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Construction Falls and Ladder Safety NewsletterFOTE REPORT – SAFETY ENGINEERING UPDATE Construction Falls and Ladder Safety
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| Duty Rating, Type | Working Load |
| Light Duty, Type III | 200 lbs. |
| Medium Duty, Type II | 225 lbs |
| Heavy Duty, Type I | 250 lbs. |
| Extra Heavy Duty, Type 1A | 300 lbs. |
The working load, as noted above in pounds, is defined as the maximum applied load, including the weight of the user plus the materials and tools, which the ladder is to support for its intended use.
ANSI’s ladder standards are very comprehensive, with each standard comprising more than 75 pages.
The testing procedures stated in each standard are both conservative and thorough. For example, a 20-foot extension ladder having a rated working load of 200 lbs. would need to withstand a test load on each of its rungs of 800 lbs.
This is accomplished by randomly selecting a rung to be tested. For example, if the tested rung has a length of 13 inches (between siderails), its maximum allowable permanent deformation is 0.13 (1/8) inch.
Ladder Safety Recommendations
• Visually inspect the ladder to check for defects.
• Do not place a ladder in front of a door unless the door is locked, blocked or guarded.
• Use a wood or fiberglass ladder, not a metal ladder, if work is near electrical equipment.
• When climbing up and down the ladder, always face the ladder and use both hands on the rails. If tools or materials need to be handled, raise or lower them with a rope.
• If using a stepladder, set the ladder on a level, firm surface and secure its spreaders.
• If using a stepladder, never climb higher than the second step from the top.
• If using an extension ladder, it should be equipped with slip-resistant feet.
• If using an extension ladder, use the 4 to 1 ratio, which places the ladder at one foot away from what it leans against for every 4 feet in height to the point where the ladder rests.
• If using an extension ladder, verify the upper and lower sections are locked.
• If using an extension ladder, the top of the ladder must extend at least 3 feet above an elevated work area, such as a roof, if access to this area is required. If not, do not climb higher than the third rung from the top.
Beil vs. Telesis Construction, Inc.
On January 19, 2011, the Pennsylvania Supreme Court upheld a lower court’s ruling in favor of Lafayette College (College), a defendant in this matter.
This case dates back to June 13, 2003, when a worker from a roofing company, Mr. David Beal, fell from scaffolding at a construction site.
That work involved the remodeling of a multi-story building on the College’s campus in Easton, Penn.
Prior to June 2003, the College hired Telesis Construction, Inc. (Telesis) as general contractor for this project.
The College entered into a written construction agreement with Telesis. Telesis provided its own on-site project manager and the College provided one of its employees as an on-site project manager.
Telesis subcontracted roofing work to Kunsman Roofing and Siding (Kunsman). The College separately contracted with Masonry Preservation Services, Inc. (MPS) for stonework repairs to the outside of the building and MPS erected the scaffolding.
On June 13, 2003, a rainy day, Mr. Beil was carrying pieces of sheet metal flashings about 2 feet by 8 feet in length. The load he was carrying weighed between 10 to 15 pounds.
While ascending a vertical ladder attached to the scaffolding, he fell about 30 feet, resulting in serious injuries to his head, neck, shoulder and heel.
OSHA requires fall protection be provided to workers on scaffolding higher than 10 feet. Such fall protection can be a stairway, which is integral to the scaffolding and includes guardrails and handrails.
Subject scaffolding had a vertical ladder that was more than 10 feet in length; therefore, to comply with OSHA’s scaffolding standard, personal fall protection is required.
For the most part, this would consist of the worker wearing a full-body safety harness. Attached to this harness would be a retractable cable, which in turn, would be securely anchored to the roof of the building.
The information presented in this case’s written review indicated the College’s project manager knew the scaffolding required fall protection. Telesis, the general contactor, testified it had complete control of the project and was responsible for safety of its subcontractors, including Kunsman and its employees, which included Mr. Beil.
On June 6, 2005, Mr. Beil filed a personal injury suit against the College, the building’s owner, Telesis, the general contractor, and MPS, the scaffolding’s owner. Before trial, the College asserted it was not liable for injuries to employees of an independent contractor or its subcontractors since the College did not retain control.
The trial court’s judge denied this legal motion and the case went to trial. On October 27, 2006, the jury found in favor of David Beil and his wife and awarded damages in the amount of $6.8 million. The jury determined liability as follows: 50% to Telesis, 35% to the College, 10% to MPS and 5% to Beil.
The College appealed to the Superior Court and on August 12, 2008, the Superior Court reversed the lower court’s trial verdict in favor of the College. The Court determined the College was not liable as a matter of law under the legal theory of “owner control.” As a general rule of law, the entity that hires an independent contractor is, for the most part, exempt from liability for injuries sustained by employees of the general contractor or its subcontractors.
For the plaintiff to prevail, he needed to successfully argue to the Court that the College “retained control” not Telesis or MPS, which was hired directly by the College and responsible for erecting the scaffolding. In order for the College to have “retained control,” MPS and Telesis would have not been “entirely free to do the work in its own way.” For example, the College may have had a right to stop work, or to inspect work, or to prescribe alternations or deviations in the work. However, these actions do not legally establish “retaining control” and therefore, the Court found in favor of the College.
The plaintiffs appealed to the Supreme Court, which on January 19, 2011 upheld the Superior Court’s ruling, finding in favor of the College.
Summarizing
Both the Superior and Supreme Courts took very firm legal stands on what constitutes owner’s control over an independent contractor, as it relates to the owner’s liability when a contractor’s employee is injured at the job site.
The College may have won legally, but this victory appears long, difficult and costly. This case’s written review is rather lengthy; it involves reading 12 pages, which are single-spaced with smaller font size and narrow margins.
Nowhere in this review was any information provided on the length of time this unsafe scaffolding had been erected on the construction site.
Generally, most contracts between the owner and general contractor require the general contractor to comply with applicable laws, ordinances, regulations, etc., which would include OSHA.
It appears some of this language was present in the contract between the College and Telesis. Also, Telesis testified it was responsible for the safety of its subcontractors’ employees such as Mr. Biel.
As noted above, this review did state the College’s project manager knew the scaffolding did not have fall protection. It would be difficult to believe the project manager for the general contractor, Telesis, did not know about this scaffolding being unsafe.
Although Mr. Beil’s employer, Kunsman Roofing, was not involved in this matter’s litigation, why did all of these entities allow this unsafe scaffolding on the job site without personal fall protection?
Over the years we have had numerous cases involving falls from elevations. Those cases included construction site falls from open, unguarded stairways and holes. Other cases related to defective ladders. At Russell Fote and Associates we were able to assist our clients in determining causes and subsequent non-controlled hazards for these types of falls, with most concluding favorably at trial or in reaching fair settlements.
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FOTE REPORT – SAFETY ENGINEERING UPDATE
Automatic sliding doors are widely used in many public buildings. The doors usually consist of two large flat panels of shatterproof glass.
Each glass panel is about three to four feet wide and seven feet high with a metal frame surrounding each panel.
These panels are electrically powered and slide horizontally to open and close, thereby providing both an entry and exit from a building.
It is not uncommon for an automatic sliding door to malfunction. The door could suddenly close, thereby striking and injuring the person who is attempting to walk over its threshold.
Some of these injuries can be severe, especially if the injured person is a young child, or is disabled or elderly.
Preventing these incidents is relatively straightforward. For the most part, that requires following the door’s instruction/owner’s manual as well as complying with ADA (Americans with Disabilities Act) requirements.
American Association of Automatic Door Manufacturers
The American Association of Automatic Door Manufacturers (AAADM) is the major trade association for automatic door safety. Its members are automatic door manufacturers and their suppliers, such as the companies that design and manufacture door sensors.
AAADM certifies automatic door inspectors, provides classroom and correspondence training programs, and prints inspection forms and door labels.
The Control System
For most automatic sliding doors, the nucleus of its control system is the main sensor, which is generally mounted above the center of the door.
When walking towards the door, one enters the sensor’s motion zone, which results in the sensor activating, thereby opening the door. Most sensors operate using microwave technology.
Microwaves have shorter wavelengths but higher frequencies than commercial radio and television transmitters and can be focused much like light waves.
With this directional property, the sensor can be adjusted to a defined activation zone so that when one enters the doorway’s zone, the transmitted microwaves’ wavelengths will be broken and the door will open.
As a safety precaution, to prevent the door from inadvertently closing and injuring a person who is in the door’s threshold, an additional sensor may be installed above the door, at the center of the door.
Its sensor zone is directed downward toward the door’s threshold.
An alternative to this second sensor above the threshold is a photoelectric beam mounted inside the door’s frame, about two to three feet above the floor.
This device uses photoelectric technology with a light beam crossing a horizontally located receiver, which is mounted on the surface of the door’s frame. When this light beam is interrupted, the door immediately reverses direction and opens.
Revised ADA Standards
Americans with Disabilities Act’s (ADA) accessibility standards were enacted in 1990 and became effective, January 26, 1992. If a business serves the public, it is most likely covered by the ADA.
There are no “grandfather” provisions under the ADA; therefore, a business owner must comply with ADA accessibility standards, if the cost to comply does not place the business in a financial hardship. ADA uses the term “readily achievable” as their guideline for businesses to comply; reference 28 CFR 36.304.
On September 15, 2010, the Federal Register published revised ADA standards for Accessible Design, which will be effective, March 15, 2012.
These standards set minimum requirements for both new construction and alterations of existing facilities. Changes mostly involve entities not previously covered by the 1990 Act, such as recreation facilities (golf, swimming, fishing, boating, etc.) and residential dwelling units.
Of interest is the revision of the accessible route’s definition relating to its location. All accessible routes connecting site arrival points and accessible building entrances are required to coincide with or be located in the same general areas as general circulation paths.
The revised ADA Standards for Accessible Design include section 404.3, Automatic and Power- Assisted Doors and Gates.
This section states automatic sliding doors shall comply with ANSI/BHMA (American National Standards Institute/Builders Hardware Manufacturers Association) A156.10-1999.
The 1999 edition of A156.10 is similar to the previous ADA cited 1985 edition, which states an automatic sliding door shall require no more than 30 pounds of force to prevent it from closing.
Also, the door’s closing speed shall not be greater than one foot per second for a door weighing 160 pounds or less per panel. If the door’s weight is greater, a formula is used to determine its maximum speed.
Daily Safety Checks
AAADM recommends each automatic sliding door be checked daily and after an electric power loss. This safety check includes walking through the door and standing motionless in the door’s threshold for 10 seconds. Then, the person checking needs to move clear of the door. The door should remain open for 1.5 seconds and then close slowly.
Also, AAADM recommends the door’s instruction/owner’s manual be followed and an AAADM certified inspector inspect the door annually.
Price vs. Frederick C. Smith Clinic
On September 27, 2010, the Court of Appeals, Marion County, Ohio, reversed a lower court’s verdict involving a case in which the plaintiff, Ms. Thelma Price, was seriously injured by an automatic sliding door.
Ms. Price, who was 90 years old and used a walker, entered the Frederick C. Smith Clinic (the clinic) on September 19, 2005 to visit her physician.
While walking through the clinic’s automatic sliding door, and at the door’s threshold, the door very suddenly started to close on her. She raised her arm to stop the door, but it continued to close, knocking both her and her walker to the floor. As a result of this fall, Ms. Price fractured her right leg.
The clinic filed for summary judgment stating it owed no duty to Ms. Price and that the automatic doors were an open and obvious danger, which the trial court granted.
Attorneys for Ms. Price appealed, stating the clinic was responsible for the doors closing on her because the clinic did not properly conduct the daily safety checks that were recommended by Stanley Access Technologies (Stanley), the clinic’s door servicing company.
Also, Ms. Price asserted the clinic was responsible for the door closing on her since the clinic did not follow the recommendation of the Stanley technician conducting routine preventative maintenance in June 2003.
At that visit, he recommended the clinic’s door sensor be upgraded to a current version. The present sensor had a blind spot and if there was no movement in the threshold for a certain period of time, the sensor would time-out, resulting in the door closing.
However, conflicting evidence was presented, which indicated the technician did check the door and that the door complied with American National Standard (ANSI) standards.
Also, there was no holding beam, which is an additional sensor installed in the sides of the doorway so that the door would not close if someone was in its threshold.
Therefore, Ms. Price’s attorneys argued the clinic chose not to upgrade their door’s sensor or install an addition holding beam sensor, which would have significantly controlled the inadvertent closing of this door.
The attorneys further argued that the clinic knew of other persons being injured by subject door. In September 2002 a woman using a walker was hit at this door’s threshold, resulting in a fractured finger. In April 2004, another woman who used a cane was knocked down in the door’s threshold; she received a fractured elbow.
There was no evidence presented which indicated any preventative action was taken by the clinic resulting from these two incidents.
The door’s next service work was performed in December 2004, by the clinic’s servicing company, Thomas Door Controls, Inc. (Thomas Door). The work completed involved the repair of a dragging door, which resulted in installing new guide rollers.
Nothing in the work order indicated the technician did any testing or inspecting of the sensors.
The clinic’s facility director testified the service contracts with Stanley and Thomas Door were for yearly inspections and maintenance of the door. If additional work and parts were required, a service order would be forwarded to him for approval.
The door in question had an inspection checklist attached to its frame. Further, the clinic’s employee performed an inspection of this door every morning at 6:30 am. This involved a walk through the door, but did not include stopping in its threshold to determine whether the door would close on the employee.
Based on the above information, the Court found the clinic’s open and obvious defense did not apply since anyone using this automatic sliding door would reasonably expect it to operate properly; therefore, no one should need to take appropriate actions to protect themselves.
The Court determined these doors were under the exclusive management and control of the clinic. Further, the clinic was placed on notice about this door’s hazard via two previous persons being similarly injured by the door.
Lastly, Ms. Price did not act in any negligent manner. In part, for these above reasons, summary judgment by the lower court was reversed.
Summarizing
Some information provided in this case’s review appears very inconsistent. A clinic’s employee checked subject door via a walk-through the door every morning at 6:30 am, supposedly following a checklist posted on the door.
However, per the information provided, this door’s checking did not include the employee stopping in the threshold to determine if the door would close on the employee.
There is no information defined in this review to indicate if this door’s attached checklist stated the need to stop in the threshold. Was this a requirement or not, and if so, why did the employee fail to follow this requirement?
Major automatic door manufacturers, such as Stanley, belong to AAADM and use their door labels or similarly worded labels. An AAADM door label/checklist states minimal daily safety checks in addition to those checks required by the door’s instruction/owner’s manual.
This label/checklist states that someone should be able to stand motionless in the threshold for at least 10 seconds without the door closing. Also, listed on this label/ checklist is the requirement to have the door inspected by an AAADM certified inspector at least annually or after any adjustment or repairs.
Nothing in this matter’s detailed review stated any information pertinent to AAADM and/or this door’s maintenance requirements per its instruction/owner’s manual, which appears very unusual.
Over recent years, our firm has had several personal injury matters involving automatic sliding doors. For the most part, ADA’s requirements and AAADM’s recommendations were not followed by the doors’ owners and in some cases, not even by the doors’ servicing companies.
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FOTE REPORT – SAFETY ENGINEERING UPDATE
Recent statistics from the National Fire Protection Association (NFPA) indicate an estimated 1,200 home fires are caused each year by propane ignition.
These 1,200 fires result in an estimated 34 deaths, 135 injuries and $48 million in property damage each year.
NFPA further estimates that nearly 90 percent of propane fires involve some type of propane-fired equipment, with the most common types being gas grills, water heaters and stoves.
Propane, also named liquid petroleum or LP gas, is manufactured as a component during the crude oil refinery process.
Propane can be stored easily under pressure as a liquid, which facilitates the fuel’s ease of transportation by rail car or truck through various distribution channels and ultimately to retail customers.
Large quantities of propane are sold annually to customers who have their 20-pound gas grill tanks filled at local retail outlets.
Propane is also delivered in bulk, for example, to large 500-gallon storage tanks installed in the yards of rural homes.
These customers usually use propane to fuel their furnaces, space heaters, water heaters, cooking appliances, and other equipment.
NFPA states the leading cause of these propane fires was a part failing or a leak. Therefore, propane leak detection is a top priority for reducing the number of fires caused by propane-fueled appliances and household heating equipment.
When a leak is discovered, the individual or individuals exposed need sufficient time to take corrective action to repair the leak, or at least escape the hazardous condition.
Propane is Odorized
When propane is manufactured from the petroleum refinery process, the final product contains no odor; an odorant is added as a primary safety precaution.
To comply with this safety requirement, NFPA developed a national voluntary consensus standard.
NFPA’s Code 58 states propane shall be odorized and detectable by a distinctive odor at a concentration in air not greater than one-fifth the lower limit of flammability, which relates to approximately one-half percent propane in air.
Ethyl mercaptan is the odorant primarily used for propane. It has an extremely pungent odor and is similar to the smell of rotten eggs.
NFPA recommends one pound of ethyl mercaptan per 10,000 gallons of liquid propane.
Detection of propane is a special problem because of its physical properties. Propane is much heavier than air, with a specific gravity of 1.5. Therefore, propane tends to seek low levels.
For example, a leak may occur in the control valve, burner or pilot mechanism of a water heater. These items tend to be near the floor.
A homeowner who uncovers a non-functioning water heater may not detect an odor when attempting to light the burner. If he or she bends to the floor with a lighted match, the propane gas may ignite, causing an explosion and/or fire and possible serious injury.
Rust, or more appropriately, iron oxide, reacts chemically with the ethyl mercaptan, thereby reducing and in some extreme circumstances, nearly eliminating ethyl mercaptan’s odorant capabilities.
New tanks with non-coated inner surfaces, which are pressure tested with water and left to dry in air, are very susceptible to forming iron oxide on inner surfaces.
Iron oxide also forms on the inner surface of refilled, used tanks whose filling valves are left open, allowing air to enter the tanks.
The Human Response
Our olfactory system consists of odor receptors in the nose, which transmit nerve impulses to the olfactory bulbs inside the brain.
The olfactory system is sensitive to various odorants and is very inconsistent. Different individuals exhibit different sensitivities to the same odor.
Age is also a factor, causing reduced sensitivity to ethyl mercaptan. A past study was conducted using ethyl mercaptan to compare sensitivity in young adults under age of 25 to adults over age of 75. The older adults required 10 times the concentration of ordorant in air to recognize the same odor level as the younger age group.
Another sensitivity factor is olfactory fatigue, which involves an individual’s perceived intensity of an odor versus time.
When exposed to an odor for a few minutes, the olfactory system becomes fatigued to a point where the odor’s magnitude appears to be only a fraction of its intensity at initial contact.
A general consensus by authorities on olfactory responses indicates odor-intensity drops by over 60 percent within two to four minutes of initial odor contact.
Also of concern is an individual’s distraction by some activity not relating to the sense of smell. Studies in this area have focused on the brain’s information processing related to odor detection.
Odors involve the brain’s limbic system, the system that also triggers our emotions. That system may play an important part in distracting us from the physiological aspects of the sense of smell.
Odor Testing and Documentation
Since propane may be stored and transported in several different tanks before reaching the final customer’s tank, it is extremely important each entity in the distribution chain conduct documented odorant testing.
NFPA’s Code 58 requires odor testing when propane is delivered from the refinery to a bulk tank distribution facility.
Most industry experts recommend odor testing and the accompanying documentation be performed by the propane retailer when filling its tank trucks for delivery to customers.
This testing may be conducted by simple smell or using an instrument such as an odor meter.
Huitt vs. Southern California Gas Co.
The California Court of Appeals on October 7, 2010 reversed a lower court’s verdict involving a natural gas explosion that seriously injured an experienced plumber, Mr. Michael Huitt and his helper, Mr. Matt Nino.
The trial court had awarded each plaintiff more than $1 million in compensatory damages, plus a total $5 million in punitive damages for the two men.
Although this case involves natural gas, safety-engineering principles concerning odor fade and warnings can easily be associated with most propane applications.
A plumbing contractor employed Mr. Hutt, an experienced plumber, and his assistant, Mr. Nino. On November 16, 2005, these men were sent to a local school’s construction site to perform work.
Once there, their first job was to light a natural gas-fired water heater, which was located in a closet. Mr. Huitt turned on the gas valve, held down the red button and pushed the igniter to light the pilot, which did not light.
Since he had lit many water heaters in the past, he did not read the instructions posted on the water heater, nor did he read the instruction manual. Mr. Huitt turned off the gas valve to the water heater and opened another gas valve to purge air from the gas piping.
He testified that after several seconds, he closed this valve and reopened the gas valve to the water heater.
Since neither he nor Mr. Nino smelled any natural gas, he proceeded to again attempt to light the water heater. At this time an explosion occurred, which severely burned both men.
At trial, testimony was presented that in nature, natural gas is odorless and an odorant is added per Federal regulations to ensure it is readily detectable for safety purposes.
The explosion site was also a construction site, and the testimony provided did not discuss the extent of how much new gas piping was present.
The odorant commonly used in natural gas is a sulfur based compound, tert-butyl mercaptan (TBM). When TBM flows through new steel pipe that contains rust and metal oxides, a chemical reaction can take place to produce disulfides, thereby causing odor fade.
A mechanical engineer retained by the plaintiffs opined there was no odorant in the natural gas because Mr. Huitt, an experienced plumber, would have smelled the odorant and therefore, would not have attempted to light the water heater.
Also, he opined Mr. Huitt was not at fault for his lack of reading the water heater’s installation manual since he had worked with a similar water heater in the past. He was not installing it but just attempting to light the water heater.
However, it was shown during the trial that the water heater’s installation manual included a warning regarding odor fade.
Also presented to the jury were several instruction manuals for other natural gas-fired appliances. Those manuals contained odor fade warnings.
Two other mechanical engineers who were experts for the defendant testified they performed calculations. They estimated the amount of time Mr. Huitt used to purge the gas piping was in the two minute range.
They evaluated the size of the closet, which contained the water heater, and the properties of natural gas. For natural gas to be ignitable, a mixture of about 5 to 15 percent of natural gas in air is required.
A defendant’s employee, a measurement technician, testified during trial that on November 16, 2005, sufficient odorant was present in the natural gas supplied to the school’s construction site. The plaintiffs did not dispute his testimony.
The plaintiffs needed to present evidence to the jury that the defendant, Southern California Gas, should have issued a warning that could have been successfully received by them, thereby preventing the injuries.
Since odor fade occurs in new steel piping, any effective warning must be directed toward the construction industry, especially those involved with new construction, such as workers and customers.
Plaintiffs’ failure to establish a causal connection between defendant’s failure to warn and their injuries resulted in the appeals court reversing the judgment entered on the jury’s verdict.
Further, it directed the trial court to enter judgment in favor of the defendant, Southern California Gas Co.
The appeals court recognized odor fade as being very hazardous and not common knowledge in the construction industry.
It encouraged the defendant and others in the industry to undertake efforts to educate those working in new construction about this hazard.
Summarizing
Our firm has been involved in several cases where the lack of sufficient odorant contributed to propane-fueled flash fires and resulting fatalities.
The first defense for injury prevention for most propane-related fires or explosions is recognizing the seriousness of the leak.
Preventative action can be initiated only through this immediate leak-recognition.
Ethyl mercaptan, the odorant used by the vast majority of propane suppliers, can fade due to reaction with the tank’s iron oxide.
Also, ethyl mercaptan can cause the loss of one’s odor sensitivity if exposed to it over a prolonged period of time or through psychological and emotional factors.
Odor fade is an on-going problem for the propane industry. The industry has attempted to address these issues through documented testing.
However, with thousands of propane suppliers, poor work practices are not uncommon and result in safety loopholes and serious injuries.
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FOTE REPORT – SAFETY ENGINEERING UPDATE
The National Safety Council estimates there are approximately 200,000 non-fatal injuries, which occur annually from rear impact collisions.
These statistics are not broken- down, but we may assume many rear impact collisions occurred at speeds less than 10 mph (miles per hour).
For example, let's assume a vehicle is stopped in traffic and another vehicle hits the stopped vehicle from behind.
Under this scenario, the torso of the driver in the hit vehicle is thrown forward; however, the head lags behind, resulting in the neck being excessively extended or hyper-extended.
The torso does not rebound until its interaction with the seatbelt, at which time it hits the seat. The head now moves forward but is snapped back once more at the neck resulting in the neck again being hyperextended.
If the vehicle's seat, along with its headrest is not designed and/or not adjusted properly, the resulting whiplash can be even more severe. This whole occurrence takes less than a second.
The Neck's Anatomy
The neck contains seven cervical vertebrae, which are numbered C1 to C7, with C referring to cervical. These vertebrae consist of seven individual and irregularly shaped bones that make up the neck's skeletal system.
C1 and C2 form the head joint, and C7 is near the shoulder. Between each bone is a large spongy mass or disc. This disc sits between two flat surfaces of each vertebra's bony surface and forms a cushion between the vertebrae.
The spinal cord travels through the center of these seven vertebrae. It contains the nerve elements that send messages from the brain to rest of the body.
The purpose of the cervical vertebrae is to protect the spinal cord from injury during motion and activity.
Cartilage, which is tough, semi-transparent, elastic and flexible tissue, connects the vertebrae on its outer surfaces. Also, cartilage helps support and form the vertebra structure of the neck.
The top two vertebra, C1 and C2, form the head joint, which enable the head to nod up and down and rotate right to left.
To strengthen this joint - which also prevents uncontrolled stretching, bending and turning movements that could injure the spinal cord - four major ligaments provide most of the support to the bones that comprise C1 and C2. Ligaments are very strong fibrous tissues and connect bones to other bones.
In addition to nerve cords, two primary arteries travel through the cervical spine. Those two arteries supply blood to the brain, near the cerebellum. This area of the brain controls the body's hearing and equilibrium functions.
The two key neck muscles involved in many whiplash injuries are the trapezius and the sternocleidomastoid, also named the SCM. Muscle is human tissue formed into filament structures. Muscle is connected to bones using tendons, which are strong fibrous tissues.
A muscle's primary purpose is to produce force and cause motion. The trapezuis muscle is an irregular shaped large muscle, which connects via tendons to the clavicle (collarbone) and the neck's and upper back's vertebra.
The SCM is attached near the back of the ear while its other end is secured to a joint between the clavicle (collarbone) and the sternum (breastbone).
The History of Whiplash
Whiplash type neck injuries started to be recorded toward the middle of the nineteenth century. At that time, it was called railway spine. Railway collisions were frequent, with both passengers and workers filing claims for personal injury.
Most of these injuries were not visible and therefore, rejected by the railroads. However, their investigations indicated most of those injured were sitting and facing forward when the trains suddenly stopped.
The next notable occurrences of whiplash injuries were during World War I. These involved navy pilots who were flying their aircraft off war ships using catapult-assisted takeoffs. The very sudden and powerful acceleration forward caused the pilots' necks to fly backward with resulting whiplash occurring.
Investigations and further analyses resulted in raising the pilot's seat so it fully supported the head and neck.
It was not until 1969 that most American automobiles were equipped with adjustable headrests. However, a headrest in a low position may provide a fulcrum for the head to bend backward rather than provide support for the head.
Also, if the driver or passenger is seated somewhat forward in their seat at the moment of impact, hyper-extension of the neck is likely to occur, even with a properly adjusted headrest.
Forces and Rear Impact Collisions
Using basic laws of physics, which relate to objects in motion and conservation of energy concepts, there are two primary equations involving low speed rear impact collisions.
The first is F = MA or force in pounds is equal to mass in slugs times acceleration, usually stated in feet per second squared. The second equation is KE = ½ MV² or kinetic energy is equal to one half the mass in slugs times velocity squared.
Using F = MA, the following example will determine the force that can be exerted on the driver's head in a low speed rear impact collision.
Assume the driver is impacted by another vehicle in the rear at a speed of 5 mph (7.3 ft/sec) and the driver's head has a weight of 10 lbs (pounds) and the collision's impact time is 0.1 second.
Using F = MA, the equation becomes 10 lbs ÷ 32.2 ft/sec² times 7.3 ft/sec ÷ 0.1 sec, which equals 22.6 lbs.
A force of 22.6 pounds on one's head during a collision may not appear to be significant, but this is only the force developed on the head as it initially moves forward during the impact. It does not take into account the rebound effect of the head hitting the seat's backrest.
It should be noted, this example uses a vehicle impacting a rigid barrier. If, for example, the rear end impact was between two similar sized sedans, energy would be absorbed by both sedans and the force to the driver's head in the hit sedan would be less. This will be discussed later.
There is some discussion based on past studies where whiplash forces to the neck (which occur during motor vehicle collisions) were not much greater than those forces that occur in everyday life.
Such incidents, for example, could include plopping down into a chair or jumping off a step. However, such activities do not take a person by surprise; one can instinctively brace the neck muscles in anticipation of these actions.
Conversely, this is not the case in a motor vehicle collision where one is completely surprised and the force to the neck is violent and sudden.
Conservation of Energy
Determining the speeds involved in low speed collisions is generally difficult since there are many variables. One of the better approaches in estimating these speeds is to use the conservation of energy law.
This law of physics states that total energy crossing a system's boundary is equal to the change in energy inside the system. For a motor vehicle collision, the equation is:
KE (pre-impact) = KE (postimpact) + Crush Energy
KE (pre-impact) is the kinetic energy of the vehicles prior to the collision while KE (postimpact) is the kinetic energy possessed by the vehicles after the collision. Crush Energy is the energy dissipated via damage to the vehicles. Updating the above equation for a rear end impact with two vehicles, vehicle (1) and vehicle (2), the equation becomes:
KE (1) pre-impact + KE (2) preimpact = KE (1) post-impact + KE (2) post-impact + Crush Energy (1) + Crush Energy (2)
The above equation may be used in an example when two vehicles are involved in a slow speed rear impact collision, where vehicle (1) hits parked vehicle (2). Both vehicles are sedans with each weighing 3000 lbs and each equipped with bumpers rated at 5 mph (7.3 ft/sec).
Since vehicle (2) at pre-impact is parked, its velocity is zero and the velocities of vehicle (1) and vehicle (2) at post-impact are both also zero since these vehicles are stopped by the impact. Therefore, the equation is as follows:
KE (1) pre-impact = Crush Energy (1) + Crush Energy (2)
½ MV² (1) = ½ MV² (1) + ½ MV²(2)
½ (3000 lbs/32.2 ft/sec²) V² (1) = ½ (3000 lbs/32.2 ft/ sec²)(7.3 ft/sec)² + ½ (3000 lbs/32.2 ft/sec²)(7.3 ft/sec)² V(1) = 10.3 ft/sec or V(1) = 7.1 mph
Vehicle (1) would have been traveling at a speed of 7.1 mph when it collided with parked vehicle (2). Again, both vehicles had bumpers that absorbed 5 mph energy with no damage and both vehicles were of the same weight.
The above example could be modified to calculate different vehicles' weights and bumpers' ratings.
During the investigation of a low speed impact collision it is essential the investigator obtain as much information as possible about the damage to each vehicle.
Where exactly did the damage occur to each vehicle? Were shock absorber bumpers involved? If there was damage to the bumper cover, which is usually constructed of hard plastic resin, were any of the bumper's steel reinforcement parts damaged, and to what extent?
Determining Delta V
Determining delta V of the target vehicle for the purpose of evaluating the potential of serious whiplash injuries in rear-impact collisions is essential. Delta V is that very sudden change of velocity of the target vehicle upon impact, which is measured in milliseconds.
This is somewhat confusing, since delta V is not the change in velocity from when the target vehicle is impacted to when it is comes to a complete stop. This velocity change usually involves a greater time frame.
Conservation of Momentum
The law of physics, which relates to the conservation of momentum, can be used in conjunction with the law of conservation of energy to determine delta V of the target vehicle.
Momentum is energy in motion, or for a motor vehicle collision, the mass of the vehicle multiplied by its velocity.
The law of conservation of momentum as is relates to a motor vehicle collision states: total momentum before a collision equals total momentum after a collision. More simply, the amount of energy entering a system is equal to the amount of energy exiting the system.
For a rear impact collision, this law states that momentum of the first vehicle plus the momentum of the second vehicle must be equal to the vehicles' total momentum after the collision or:
M(1)V(1) + M(2)V(2) =
M(1)U(1) + M(2)U(2)
M(1) is the mass of vehicle one (1) and M(2) is the mass of vehicle two (2). V(1) is the velocity of vehicle one (1) and V(2) is the velocity of vehicle two (2), both before the collision. U(1) is the velocity of vehicle one (1) and U(2) is the velocity of vehicle two (2), both after the collision.
Using conservation of momentum and relating it to the previous example, the change of velocity of vehicle two (2) upon impact may be determined. For the purpose of this calculation we are assuming the velocity of vehicle one (1) is U(1) and the velocity of vehicle two (2) is U(2) and this velocity is the same upon impact. Also, this velocity is the change of velocity of vehicle two (2) or its delta V. Therefore, using the equation:
M(1)V(1) + M(2)V(2) =
M(1)U(1) + M(2)U(2)
M(1) and M(2) are the masses of the two vehicles, which are each 3000 lbs ÷ 32.2 ft/sec².
V(2) is the velocity of vehicle two (2) before the collision, which is zero.
V(1) is the velocity of vehicle one (1) before the collision, as calculated earlier, which is 10.3 ft/sec.
U(1) and U(2) are the velocities of vehicle one (1) and vehicle two (2) upon impact and are the same, therefore, U(1) = U(2).
(3000 lbs ÷ 32.2 ft/sec²)(10.3 ft/ sec) = (3000 lbs ÷ 32.2 ft/ sec²)U(2) + (3000 lbs. ÷ 32.2 ft/ sec²)U(2) 10.3 ft/sec = 2U(2) or U(2) = 5.2 ft/sec.
Coefficient of Restitution
For the above example, delta V or the change in velocity of vehicle two (2), the target vehicle is 5.2 ft/sec. The delta V of 5.2 ft/sec is assuming there is no rebound effect between the two vehicles upon impact.
The bumpers on each vehicle are equipped with shock absorbers; therefore, the collision is elastic, since there is no damage to the bumpers.
The total change in velocity is the resulting change in velocity during the vehicles initial impact up to their maximum crush plus the change in velocity that occurs during the separation of the vehicles.
This difference is the coefficient of restitution, which is defined as the ratio of the difference in the impact and rebound velocities, which is:
e = [U(2) ÷ U(1)] ÷ [V(1) ÷V(2)]
For near plastic impacts, usually at moderate to high speeds and involving significant permanent damage to the vehicles, there is little to no rebound effect; therefore, the coefficient of restitution approaches zero.
However, for completely elastic impacts usually at low speeds where no permanent damage occurs, the coefficient of restitution approaches 1. For impact speeds under 10 mph, the coefficient of restitution generally ranges from 0.2 to 0.4.
If we combine the conservation of momentum equation with the coefficient of restitution equation where pre-impact velocity of vehicle two (2) or V(2) is zero and we wish to find the change in velocity of vehicle two (2) at instant of impact with vehicle one (1), we would need to solve for U(2), which is also delta V under this condition. This equation becomes:
U(2) = M(1)[1 + e]V(1) ÷ [M(1) + M(2)]
Since M(1) equals M(2) and the coefficient of restitution is estimated at 0.3, our example becomes, U(2) = (1 + 0.3)(10.3 ft/sec) ÷ 2 = 6.7 ft/sec or 4.6 mph.
This is also delta V for vehicle two (2) upon impact since delta V for vehicle two (2) is equal to the velocity of vehicle two (2) upon impact minus the velocity of vehicle two (2) prior to impact. Therefore, delta V equals U(2) - V(2) and if V(2) is zero, then U(2) equals delta V.
Once delta V is determined for vehicle two (2) upon impact, the primary force exerted upon this vehicle at the time of impact can be calculated.
That force is also the force which is transmitted to the occupants in this vehicle.
Most collisions are in the 0.1 second time frame and force is proportional to acceleration, which is the change in velocity per unit of time.
For the above example, delta V is 6.7 ft/sec and if collision time is 0.1 second, then acceleration or in this example de-acceleration, is determined by dividing 6.7 ft/sec by 0.1 second, which equals 67 ft/sec².
If acceleration due to gravity is 32.2 ft/sec², then this collision generates over twice the force of gravity upon this vehicle's occupants.
Summarizing
The anatomy of the neck is very complex with its many bones, ligaments, muscles, arteries and nerve cords.
Compounding this complexity is the closeness of the C1 and C2 vertebrae to the brain. Also involved in this complexity are the arteries and nerve cords that travel through the cervical spine to the brain.
These are immediately adjacent to the cerebellum, which controls the body's hearing and equilibrium functions.
All of these sensitive components of the neck are affected in a rear impact and low speed induced whiplash collision.
There were numerous studies conducted over the past 15-plus years, which link the seriousness of whiplash injuries to the change in velocity of the vehicles being impacted, that being delta V.
Delta V is the very sudden change in velocity of the vehicle being impacted, which is measured in milliseconds.
These studies generally point to a greater chance of injury when delta V is more than 5 mph. For the most part, these studies are based on healthy adults that were seated in automobiles with properly adjusted headrests and were restrained with a seat belt.
As was noted above, significant amounts of information need to be collected prior to determining delta V. Collision site data must be gathered such as specific damage to vehicles and of course, some vehicles' specifications are required. Once all this information is collected, then various estimates are made so calculations can be performed.
Our firm has had several low speed motor vehicle collision cases, which involved our investigation, submission of a report and in some cases expert testimony. All of these were successfully settled before trial.
FOTE REPORT – SAFETY ENGINEERING UPDATE
Fall Statistics
The most recently published injury statistics concerning falls are from the National Safety Council. Based on statistics compiled in 2006, an estimated 12,000 fatalities occur annually in the U.S. from falls involving level or near level walk surfaces.
Many of these fatalities happen to individuals who are 75 years and older.
Walk Surfaces and Fall Prevention
Preventing falls on walk surfaces requires us to address characteristics of floor materials and finishes, shoe bottom materials and textures, possible floor surface contaminants and individuals’ walking gaits.
Obviously, there is no practical way to control a person’s walking gait or type of shoe worn in a public facility. However, floor conditions and maintenance are very controllable factors.
Most falls on a level surface occur when a person slips on a wet area made slippery by water or other contaminants. Slip-resistant floor surface materials are important in preventing falls, as is proper floor maintenance.
Application of a non-slip wax is the first step in good floor maintenance. Most major janitorial supply vendors have cleaning and wax products, which can help to provide greater slip resistance to various walk surfaces such as wood, concrete, vinyl and ceramic tile.
Remedial floor maintenance, including clean-up of spills or removal of ice and snow, may require a formal safety program involving, for example, on-going inspections, a written log, and use of temporary warning signs.
It needs to be stressed warning signs posted near spills or hazardous floor surface conditions are only a temporary measure; they are not a substitute for taking the necessary actions to eliminate or control hazards.
Floor mats are also useful in controlling slippery walk surfaces. Mats assist in cleaning and drying pedestrians’ feet, especially upon entry to buildings. For mats to be effective, they need to lay flat, not have curled up edges, and be resistant to movement.
Different locations, which may be an entryway to a department store or the floor surface under an ice machine in a motel lobby, may require different kinds of mats.
Most vendors will assist their customers in purchasing the type of mat that fits the intended application.
Coefficient of Friction (C.O.F.) (Dry Conditions)
Most pedestrians are usually aware of C.O.F. as being the resistive experience between a floor’s surface and one’s footwear.
A very slippery floor, such as polished marble, would then have a low C.O.F., while a recently sandpainted floor would not be slippery or would have a high C.O.F.
A widely accepted definition, currently used by the National Institute of Standards and Technology (NIST), defines coefficient of friction, under static conditions, as the horizontal force required to initiate relative motion between an object and the horizontal surface it is resting on.
For example, if a five-pound horizontal force is required to move a ten-pound block resting on the floor, the coefficient of friction is 0.5.
NIST also has another definition for coefficient of friction: If an articulated strut instrument is used, the tangent of the angle from the vertical that is created when the attached strut’s shoe begins to slip is defined as coefficient of friction.
Since this definition requires direct contact between the object and the surface, C.O.F. must be used only under clean and dry surface conditions.
Slip Resistance (Wet Conditions)
By definition, C.O.F. of a walk surface can only describe the slippery condition between an object, such as a person’s shoe, and the walking surface, such as a floor. A contamination, like water on the floor, thus prevents us from measuring C.O.F. and therefore, we are only capable of measuring a floor surface’s slip resistance under wet conditions.
To measure slip resistance under wet conditions, portable variable angle tribometers (VAT) were developed (tribo in Greek means to rub). These instruments are mechanical and use a test foot attached to an articulated strut. When this test foot is in motion, it contacts the testing surface in a manner similar to one’s shoe contacting a walk surface.
The test foot’s contact angle, which is a ratio of the horizontal force to the vertical force, is adjusted by the instrument’s operator. This adjustment changes the angle of the test foot hitting the floor’s surface until a slip occurs, at which point that angle is read from the instrument’s scale.
This scale ranges from a minimum of zero to a maximum of one and is divided into one-tenth intervals. Values closer to zero relate to less slip resistance for the walk surface while higher numbers, which approach one, relate to a walk surface with greater slip resistance.
The American Society for Testing and Materials (ASTM) recognized the need to establish standards for two VATs. ASTM standards for testing slip resistance under both wet and dry surface conditions were issued in 1996; F1677-96 and F1679-96. The F1677 standard determines slip resistance using the Brungraber Mark II.
The F1679 standard determines slip resistance using the English XL.
Both of the above instruments measure coefficient of friction, C.O.F., on dry surfaces under static conditions. Their measured data, for the most part, correlates with data generated by other portable and static coefficient of friction testers.
The main advantage to these two instruments is the capability of measuring slip-resistance under wet surface conditions. Other surface testing meters can produce faulty readings due to adhesion conditions between the instrument and the wet floor surface, which is similar to the situation that occurs when sliding two pieces of glass together with wet surfaces. However, the Brungraber and English instruments can measure slip resistance effectively under wet surface conditions.
Establishing 0.5 Slip Resistance Threshold
The first articulated strut instrument used to measure C.O.F. on floor surfaces is the James Machine, which was developed in the 1940’s by Mr. Sidney James, an employee of Underwriters Laboratories. It uses an articulated arm, which is attached to a test foot with a leather surface.
C.O.F. is determined when the angle of the instrument’s test foot slips upon contact with the tested surface. That measured angle is then used to calculate C.O.F.
The James Machine is bench mounted. It cannot be operated as a field instrument, such as to test a building’s floor surface. Also, it cannot test floor surfaces under wet conditions.
This instrument continues to be inservice and has a current operating standard, ASTM D2047, Standard Test Method for Static Coefficient of Friction of Polish-Coated Flooring Surfaces as Measured by the James Machine.
What is significant is that Mr. James determined a C.O.F. threshold for a safe walk surface to be 0.50.
As explained above, slip resistance is different than C.O.F since only slip resistance can be measured under wet conditions. Slip resistance uses an index system, which ranges from a minimum of zero to a maximum of one.
Again, those numbers closer to zero represent more slippery conditions while the numbers closer to one represent a much higher slip resistance.
Current consensus on a slip resistance threshold is discussed in ANSI/ASSE (American National Standards Institute/American Society of Safety Engineers) technical report, TR-A1264.3, published February 2008. This report states the following: “0.50 has emerged as the default threshold, and is the most recognized and accepted reference value in the U.S. for pedestrian safety.”
TR-A1264.3 further states: “A majority of slip and fall incidents occur as a result of contact with a spot on the floor surface that is unexpectedly slippery, usually due to moisture. It is important to determine how slip resistant the surface is under dry and wet conditions because of pedestrian expectation.”
Mincy vs. Parsippany Inn
The Superior Court of New Jersey, Appellate Division, decided a case on Nov. 8, 2010 in favor of the defendant in which the plaintiff, Ms. Candi Mincy, fell in the bathroom at defendant’s motel, Parsippany Inn. The Court affirmed the lower court’s summary judgment, which was in favor of the defendant.
Plaintiff and her husband arrived at the defendant’s motel on July 16, 2007 and stayed at the motel until the date of Ms. Mincy’s fall, July 22, 2007. On that morning, Ms. Mincy was in the bedroom and proceed to the bathroom to wash her hands; she was barefoot.
As she walked towards the sink, she took a couple of steps and fell on something she stated felt like ice.
She testified she did not observe any water on the floor and the last time she or her husband took a shower was the previous morning.
Her husband testified he saw water on the floor after her fall and estimates more than a cup of water was present. Using a photograph of the bathroom, he was able to point to the water’s location on the floor, but could not testify how the water got on the floor. Ms. Mincy suffered severe injuries to her leg, ankle and foot.
Plaintiff’s attorney retained an engineering expert to test the bathroom’s floor surface for slip resistance, which was conducted on Oct. 1, 2007.
Slip resistance measurements for the ceramic tiled floor were recorded at 0.74 when dry and 0.24 under wet conditions.
Under oral argument, the judge questioned the engineering expert at what point between 0.24 and 0.74 would a safety hazard be present. The expert cited the Ceramic Tile Institute of America, which states no such number exists.
Since no standard for “safe” slip resistance could be cited by the expert, plaintiff could not establish defendant’s breach of duty. Therefore, the judge affirmed the lower court’s ruling when it granted summary judgment to the defendant.
Two questions immediately surface: First, why did plaintiff’s testimony significantly conflict with her husband’s testimony÷ Ms. Mincey testified she did not observe any water on the floor while her husband said he saw over a cup of water on the floor.
Second question: What instrument did the engineering expert use to test the floor surface’s slip resistance under dry and wet conditions÷
There are only two instruments recognized by ASTM (American Society for Testing and Materials), the English XL and the Brungraber Mark II, to conduct such testing.
The inventor of the English XL, Mr. William English, authored a book, Pedestrian Slip Resistance, How to Measure It and How to Improve It, which was published in 2003.
In his book, Mr. English discusses 0.50 as the safety threshold for slip resistance on both wet and dry surfaces and further substantiates this number with many reference resources.
One would assume most users of the English XL would have read Mr. English’s book. Also, as previously discussed in this article, ANSI/ASSE TR-A1264.3 cites the use of the English XL and the Brungraber instruments along with the recognized safety threshold of 0.50 slip resistance.
Based on the above information, it does not appear this expert used the English XL or had any knowledge of the English XL or Brungraber instruments or 0.50 as the safety threshold for slip resistance.
Summarizing
ANSI/ASSE TR-A1264.3, in essence, validates the use of the English XL and the Brungraber Mark II/III as reliable VAT instruments for measuring slip resistance on both wet and dry surfaces. Also, TR-A1264.3 states many slips and falls occur from pedestrians’ unexpected contacts with contaminated wet spots on walking surfaces. Therefore, it is important to determine how slip resistant the surface is under dry and wet conditions.
Our firm has had numerous cases involving the measuring of slip resistance under both dry and wet conditions. Most of these matters were settled before trial; however, some were tried, which resulted in us successfully demonstrating the English XL before the jury.
Did You Know
The safety community mourns the loss of Mr. William “Bill” English who died unexpectedly on April 14, 2010. Bill was a floor safety expert, a pioneer, researcher, and inventor of the English XL slip resistance instrument.
Very fortunately, several months prior to his death, Bill sold his business to Excel Tribometers, LLC, a safety consulting firm headed by Mr. George Widas.
Mr. Widas is a professional engineer, certified safety professional and has over 30 years of experience in the field of safety engineering. Excel Tribometers continues to manufacture the English XL, conducts training seminars and performs recalibrations and repairs for these instruments.
FOTE REPORT – SAFETY ENGINEERING UPDATE
The National Fire Protection Association (NFPA) released a report late last year titled “Burns Seen In Hospital Emergency Rooms in 2008 by Burn Type and Victim’s Age.”
Statistics in this report were gathered using the National Fire Incident Reporting System (NIRS), which is comprised of local fire departments as well as state and federal fire authorities.
For 2008, an estimated 216,000 individuals visited hospital emergency rooms because of various burn injuries.
These injuries were categorized as follows: 42 percent thermo burns from non-fire causes such as contact with a hot radiator, 28 percent (60,000) scalds, 13 percent thermal burns from fire causes and 17 percent miscellaneous.
Although not specifically stated, we may expect many of the 60,000 scalds reported resulted from too hot tap water.
Children under the age of 15 were the most susceptible to scald burns. They comprised 36 percent of the total scalds reported, which is over 21,000 burns.
Anatomy of the Skin and Burns
Human skin is comprised of two distinct layers, the epidermis and the dermis. The epidermis is the most outer layer of skin that contains skin cells but has no blood vessels or nerve endings. Its thickness is about 0.8 mm.
The next skin layer is the dermis; it contains blood vessels, nerve endings and has thickness of about 2 mm. A first-degree burn causes minor harm to the epidermis but no permanent damage. Most discomfort from a firstdegree burn results from exposure of the superficial blood vessels, which causes reddening of the skin.
A second-degree burn involves damage to both the epidermis and the dermis, generally resulting in blistering the epidermis.
A third-degree burn involves more damage to the dermis than a seconddegree burn resulting in open sores. These burns cause permanent skin damage, the formation of scar tissue and require skin grafts.
For the purpose of our discussion, serious burns will be defined as fullthickness, that being the complete destruction of the epidermal. Serious burns include all third-degree burns and many second-degree burns.
Time-Temperature Relationship
Most adults know contacting very hot water can result in a burn. However, most adults don’t know contact with, for example, 150 F water will cause a serious skin burn in two seconds, or that serious burns will occur with a six second exposure with 140 F water, or a 30 second exposure with 130 F water.
This time-temperature relationship of hot tap water contact and serious skin burns dates back to the 1940s when research was conducted at the Harvard Medical College by researchers, A.R. Moritz, M.D. and F.C. Henriques, PhD.
Using both animals and humans as test subjects, their findings were published in 1947 by The American Journal of Pathology.
Past Studies
Two major studies involving in part, tap water scalds, were released in 1975 by the U.S. Consumer Products Safety Commission (CPSC).
The first study was written by Calspan, a CPSC contractor, which was issued under “The Investigation of Safety Standards of Flame Fire Furnaces, Hot Water Heaters, Clothes Dryers and Ranges.”
The other study was performed by another CPSC contractor, ABT Associates, and its report titled: “A Systematic Program to Reduce the Incidents and Severity of Bathtub and Shower Area Injuries.”
Both of these studies cite the timetemperature burn relationship of hot tap water, as reported by researchers Moritz and Henriques in 1947.
NEISS (National Electronic Information Surveillance System) data was used to obtain injury statistical sampling of hospital emergency rooms. The studies indicated the need for scald devices and to set water heater thermostats at 120 F.
The study also cited the Massachusetts state plumbing code 1973-1974, which required anti-scald devices.
Thermostat Settings
During the 1970s, residential water heater manufacturers’ instruction manuals cited 140 F as a normal thermostat setting.
This changed in the early 1980s to a normal setting of 130 F and that setting was changed again in the early 1990s to 120 F.
Scald Warnings
During the early to mid 1980s, water heater manufacturers began placing warnings on their products. Printing on thermostat knobs stated: “Caution Hotter Water Increases the Risk of Scald Injury.” Also, printed warnings were attached to water heaters citing water over 130 F may cause scalding.
In 1991, the water heater manufacturers consensus standard (ANSI) American National Standard Institute Z21.10.1a-1991 included a pictorial scald warning depicting a possible burned hand under a bathtub’s hot water spigot. The warning states: “Danger, Water Temperature Over 125 F Can Cause Severe Burns Instantly or Death From Scalds.”
Plumbing Codes
There are three major U.S. plumbing codes, Uniform Plumbing Code (UPC), Standard Plumbing Code (SPC), and the International Plumbing Code (IPC).
Since the early to mid-1990s, these codes had sections addressing scald protection for new and remodeled construction. Their wording is similar to: “Shower and tub/shower combinations shall be provided with pressure balance or thermostatic mixing controls. Such valves shall be equipped with handle stop positions and shall be adjustable to deliver water at a maximum of 120 F.”
Although existing installations may be exempt from providing specific scald protection, the Codes’ language does indicate the need to provide a safe installation such as: “The plumbing and drainage system of any premises under the Authority Having Jurisdiction shall be maintained in a sanitary and safe operating condition by the owner or the owner’s agent . . . . . no hazard to life, health or property is created by such plumbing system.”
There is general agreement in the plumbing industry that tap water temperatures above 120 F are not safe and proper precautions are required to reduce this scalding hazard.
Scald Protection
For residential applications, the most widely used device for preventing tap water scalds is the pressure balancing control valve. As stated above, these devices were required by plumbing codes starting during the early to mid 1990s.
These would be installed as either the control valve for the combination tub and shower unit, or for just the shower stall. Most of these valves are designed with a flexible diaphragm in combination with a cylinder bored with two holes, one for hot water and one for cold water. The edges of the diaphragm serve as valve seats, which control the both the hot and cold water entering and exiting the valve.
For example, when taking a shower, if cold water is activated in the home such as a flushed toilet, cold water pressure may suddenly drop and hot water would not be thoroughly mixed with the cold water thereby, causing much hotter water to exit the showerhead.
With a pressure balancing valve, a drop in pressure of cold water would move the cylinder inside the diaphragm toward the cold side, allowing more cold water to enter the control valve and less hot water.
This is accomplished almost instantaneously so the person taking the shower would not be affected by changes in water temperature.
The key to proper operation of a pressure balancing control valve is its initial setting.
For example, to ensure maximum hot water exiting the valve is 120 F, the control lever’s maximum hot water position must be set. This usually involves adjusting a set-screw while using a thermometer to measure the exiting tap water.
In the past these devices were required only for stand-alone showers and combination shower and bathtubs, not bathtubs without showers such as those equipped with whirlpool jets. However, current plumbing codes now require similar scald protection devices for these types of installations.
Scald protection can be provided for older existing applications, which do not have pressure-balancing valves. There are add-on thermostatic control devices, which attach to sink spouts, showerheads and bathtub spigots.
Usually these devices are factory set at 114 F for exiting hot water. If water above this temperature contacts the device, it will stop the hot water exiting the spout or spigot. Most individuals take showers or baths using water between 105 and 110 F.
For commercial hot water applications such as hotels, schools and apartment complexes, a combination mixing and thermostatic valve is generally installed. Such a master valve is usually attached to the main hot water pipe as it exits the water heater. The cold water supply pipe also enters this valve; a mixing action occurs, which results in tempered water exiting the valve. This tempered water, usually at 120 F, is then piped for tap water use throughout the building.
Legionella Bacteria
Some experts contend lower water temperatures allow growth of Legionella bacteria. Legionella bacteria was named after the lung disease that killed dozens of American Legion conventioneers attending a convention in a Philadelphia hotel during the mid 1970s.
This bacteria flourish at water temperatures between 68 and 122 F, usually on water slime, bio-film, sediment and scale. The assertion is Legionella bacteria can form at relatively low hot water temperatures, which are then released and inhaled when taking a shower. To date, the majority of Legionella bacteria were found in large commercial buildings and none have been found in residential homes.
Layering Phenomenon
Thermostats on residential water heaters are not precise controls of water temperature. ANSI Z21.10.1 standard for residential water heater manufacturing allows gas fired water heaters to vary ten degrees above or below the thermostat setting.
Also, allowed by ANSI Z21.10.1 is the phenomenon known as stacking or layering. Short repeated draws of hot water from the water heater could cause changes in water temperature within the water heater itself.
This is due to the inherent design of residential gas fired water heaters where the thermostat and burner are near the bottom of the tank, with cold water entering the top of the tank and hot water exiting at the top of the tank.
This layering phenomenon can increase as much as 30 degrees F to the hot water exiting the tank versus the thermostat setting. Although rare, it is possible and it reinforces the need for applicable scald protection devices and warnings.
Liability Issues
Since 1996, our firm has been involved with over three-dozen scald cases involving excessively hot tap water. Some cases centered on landlord liability, which pertained to the necessity of maintaining a safe property for tenants.
Other cases focused on contractor liability, such as improper installation of the water heater. Product liability issues were also involved, usually against the water heater manufacturers, primarily for inadequate warnings.
Under the ANSI standard, the manufacturer is required to use a detent or legible mark on the heater’s adjustable thermostat, consistent with a water temperature of approximately 120 F. Each thermostat manufacturer uses a different type of adjustable dial for temperature settings.
For example, one manufacturer states their “Hot” setting approximates 120 F. Another manufacturer states the setting that approximates 120 F is at the detent about 1/3 the distance between their “Warm” and “Hot” marks.
Although these settings are usually fully explained in the manufacturer’s instruction manual, these may or may not be explained on the water heater itself. Simply, in order to properly set the water heater’s temperature at or, at least near 120 F, a consumer is required to read the manual.
This may seem obvious, but if the instruction manual is not available, a consumer then needs to rely on trial and error in establishing a proper thermostat setting. That, of course, is just not safe.
Preventative Action
First, if the home’s water heater is gas fired, check the setting of the thermostat on your water heater.
The heater’s thermostat control knob is usually visible on the outside of the heater. As noted above, this may require the need to refer to the water heater’s instruction manual.
If the setting is incorrect, reset the control knob according to the manual’s instructions for 120 F water.
If you reset the thermostat, wait a day before you test the water temperature. To test, start with the tap closest to the water heater. Run the water for at least several minutes over a candy or meat thermometer and then read the temperature.
If the tap water check indicates the water is too hot, simply turn the control knob to a lower setting.
Wait a day and then recheck the same tap water to ensure a 120 F temperature.
If the water is still too hot, repeat the above procedure to attain the correct temperature.
The thermostat on an electric water heater is located under a metal cover, which needs to be removed with a screwdriver. You will definitely need to read your heater’s instruction manual before attempting to reset the thermostat.
Remember, first turn off the main electrical connection to the water heater, either by switching a circuit breaker or by pulling a fuse. If the procedure appears difficult or confusing, we recommend you contact a service technician.
Summarizing
Preventing serious tap water scalds is relatively easy. First, you must realize the hazards of too hot tap water. You then need a basic knowledge of your water heater’s thermostat function. Finally, you must conduct a simple test to ensure 120 F water.
FOTE REPORT – SAFETY ENGINEERING UPDATE
The NFPA (National Fire Protection Association) estimates 480 deaths occur annually from carbon monoxide (CO) poisoning relating to exposures from non-fire causes.
Those deaths relate to hazards involving motor vehicle exhaust, home heating equipment, cooking appliances and engine-driven equipment such as lawn mowers, generators, etc.
Annually, over 60,000 non-fire carbon monoxide incidents are reported to responding fire departments, with nearly 90 percent of these incidents occurring in the home.
Carbon monoxide is formed as a result of an incomplete combustion process, which involves all carbon-based fuels, such as propane, oil, natural gas, wood and coal.
Under ideal combustion conditions, a fuel's carbon molecules mix with air's oxygen molecules to form carbon dioxide; however, if lack of oxygen is present, deadly carbon monoxide is formed.
Carbon Monoxide and Oxygen Starvation
The molecules of the red blood cells, hemogoblin, which normally attach to the oxygen molecules to form oxyhemogoblin will combine instead with carbon monoxide to form carboxyhemoglibn. This process starves oxygen to the vital tissues, such as the brain.
Inhalation of carbon monoxide can affect one's memory and thinking, which in turn, leads to dizziness, fatigue and confusion. Carbon monoxide can kill within minutes.
Breathing air with only a 1.3 percent concentration of carbon monoxide will almost immediately cause unconsciousness and possible death in one to three minutes.
A concentration of carbon monoxide in air just below one-fifth of one percent can cause nausea within 20 minutes and death within an hour.
Serious non-fatal exposure to CO is marked by symptoms of memory loss and confusion, with possible resulting permanent brain damage and total disability.
The Occupational Safety and Health Administration (OSHA) requires a carbon monoxide exposure limit based on an eight hour average day of no more than 50 parts per million or 5/1000 of one percent.
CO and its Attributes
CO is very difficult to detect since it is odorless, colorless and tasteless. Low levels of carbon monoxide exposure generally result in headaches, dizziness, overall weakness, nausea and other flulike symptoms.
Prolonged exposure to low levels of CO can result in permanent brain damage and total disability.
Also, carbon monoxide is only slightly lighter than air, with a specific gravity of 0.97. This allows CO to intermix with air and travel freely throughout the home and into secondfloor bedrooms.
A Defective Venting System
A major cause of CO entering living spaces is a defective venting system. To discuss this danger, let's first look at the fundamentals of a venting system for gas-fired appliances.
A draft is defined as the flow of exhaust gases and air through a chimney or flue pipe to the outside.
Natural draft is developed by the temperature difference between the hot gases exiting the gas-fired appliance and the surrounding cooler, ambient air.
Hot gases are lighter than the surrounding air and that weight or density difference creates buoyancy, like a cork in water.
The heavier surrounding ambient air descends downward and around the appliance, which forces the hot vented gases upward through the flue pipe and/or chimney.
To facilitate these buoyant conditions effectively, sufficient amounts of cooler ambient air surrounding the appliance are necessary, both for proper combustion and draft. When the venting system is not functioning properly, vented gases are most likely, backing up into the living space, a condition known as back drafting.
Combustion Air
For complete burning, a natural gas appliance requires 10 cubic feet of air for every one cubic feet of gas burned. During combustion, natural gas, CH4, ignites with air containing oxygen, O2, and nitrogen, N2, to produce heat, light, water vapor, carbon dioxide, CO2, and nitrogen. If insufficient air is available for combustion, CO is produced, instead of CO2.
Along with the combustion requirement, additional ambient air is needed to surround the venting gases to produce a draft necessary to move the hot gases up the flue pipe and/or chimney.
The air required to produce both complete combustion and to facilitate adequate draft is referred to as combustion air.
Confined Space
The requirement for adequate combustion air is defined by NFPA 54, National Gas Code, which states a confined space is a space where its volume is less than 50 cubic feet per 1,000 Btu/hour of total input ratings of all appliances in the space.
If the space meets the criteria as a confined space, the Code requires two air openings be provided for combustion air to enter the confined space. Each opening is to be sized based on the requirement of 1,000 Btu/hour of total input ratings of all appliances in the confined space.
The top opening is to be within 12 inches from the top of the space, and the lower opening is to be within 12 inches from the bottom of the space.
For example, let's assume a home's space contains an older 80 percent efficient gas-fired furnace with an input rating of 50,000 Btu/hour and a gas-fired water heater with an input rating of 30,000 Btu/hour. This space measures 24 feet by 24 feet by 8 feet high or 4,608 cubic feet of volume.
If 4,608 cubic feet is divided by 50 cubic feet/1,000 Btu/hour, this equals 92.16. Therefore, per Code, a total of 92,160 Btu/hour of input rating appliances may be installed in this space.
The furnace in this example has an input rating of 50,000 Btu/hour and the water heater has an input rating of 30,000 Btu/hour for a total of 80,000 Btu/hour, which is less than the maximum calculated amount of 92,160 Btu/hour.
Therefore, these two appliances may be installed in this space with no additional air openings required.
Now, assume we wish to install a gas-fired clothes dryer with an input rating of 20,000 Btu/hour into this space. The total input rating of all three appliances would be 100,000 Btu/hour, which is higher than the Code's limit of 92,160 Btu/hour.
Under these conditions, two combustion air openings would need to be provided for this space to allow air from the outside or from an adjacent inside room to enter.
To access air from an adjacent room, two openings would need to be installed, each providing 100 square inches (1 square inch for every 1,000 Btu/hour of input rating).
One 100 square inch-opening would need to be within 12 inches from the top of the space and the other 100 square inch-opening would need to be within 12 inches from the bottom of the space.
Carbon monoxide poisoning caused by lack of combustion air tends to involve very confined spaces, such as a closet or small utility room containing a gas-fired furnace and a gas-fired hot water heater. If these conditions are present, CO tends to be produced erratically and therefore, it may be difficult to measure CO levels using a CO meter.
One means to determine the extent of a CO problem involving a confined space having, for example, gas-fired appliances inside a small utility room, such as a furnace and water heater, is to check the levels of CO in each appliance's vented gases.
Generally, a lack of combustion air will cause the appliance's burners to soot and clog resulting in poor combustion and high levels of CO in its vented gases.
Over 100 ppm (parts per million) of CO in the appliance's vented gases is a very suspect condition that the appliance is not operating properly. Therefore, more CO testing of the air in the confined space and in the home's living space is necessary.
Our firm has been called upon for several carbon monoxide poisoning matters involving gas-fired appliances being installed in confined spaces. Those matters were successfully investigated and resolved prior to trial.
Issues with Chimneys and Flue Stacks
Plugged or partially plugged chimneys or flue stacks can result in back drafting and CO entering the living space. One primary cause is animals, such as birds, squirrels and raccoons, nesting in the flue stack or chimney. The most effective preventative measure is installing flue or chimney caps.
Another cause of CO entering a living space is a chimney or vent pipe, which was constructed from single-wall galvanized sheet metal. Over time, the metal will rust and/or separate at its connections, resulting in cracks for CO to escape.
These flue pipes are especially dangerous if they were installed in concealed spaces, for example, between walls or nailed-off attics.
The National Gas Code, as far back as the 1960's, prohibited single-wall metal flue pipes from originating in any unoccupied attic or concealed space and passing through any attic, inside wall or floor that is concealed.
The Code cites the use of double-wall metal pipe for flue construction. That pipe has an inside pipe constructed of aluminum to prevent corrosion, and an outside pipe constructed of steel for strength.
Our firm has investigated two matters involving the use of single-wall vent pipes that were installed in concealed spaces. Those pipes had corroded and separated, resulting in CO entering the living spaces and killing the inhabitants.
Carbon Monoxide Detectors
An excellent prevention tool is a CO detector, preferably installed in a hallway near the bedrooms. In the past, these detectors were prone to setting off false alarms.
Today's detectors meet current Underwriters Laboratory Standard, UL 2034, and are designed to sound an alarm only when detecting dangerous concentrations of CO.
A carbon monoxide detector will assist in providing an advanced warning before very dangerous CO concentrations are incurred. Their cost is usually less than $50.
Summarizing
CO is a very deadly gas. Breathing air containing just over one percent CO causes almost immediate unconsciousness and death within minutes.
To prevent CO poisoning in your home involving your home's fuel heating equipment, annual checks need to be conducted. Such checks should include, for example, the furnace, space heater, water heater, fireplace, wood stove, etc. and are recommended before the beginning of the winter heating season.
Also, these checks need to ensure the flue pipes are tight and not corroded, and the chimney is clear of any debris. Also, if you do not have a CO detector in your home, please install one as soon as possible.
Russell Fote & Associates, Inc.
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Email: rfote@wi.rr.com
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