PPE

Fired up

A close look at flame-resistant clothing standards

September 1, 2011
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Despite clear OSHA requirements for fire hazards1, many industrial organizations do not give the same attention to flame-resistant (FR) clothing as other personal protective equipment (PPE). This article will attempt to provide perspective on how to properly address the hazard of thermal exposure and fires in the workplace.

Standard misconception

Let’s start with a discussion of applicable standards. There is a perception with many industrial professionals that simply providing workers with garments compliant to the National Fire Protection Association NFPA 2112 Standard on Flame-Resistant Garments for Protection of Industrial Personnel Against Flash Fire is all that is needed to meet OSHA regulations. Regrettably, unless the requirements of 29 CFR 1910.132 have been satisfied (to include an applicable hazard assessment of the fire hazard, PPE protection assessment, training in use, etc.), compliance has not been met1 irrespective of the fire hazard scenarios that exist in the workplace. Actually, the industry consensus standard that OSHA generally recognizes as meeting the requirements of the PPE standard for development and implementation of FR garment programs is NFPA 2113 Standard on Selection, Care, Use, and Maintenance of Flame-Resistant Garments for Protection of Industrial Personnel Against Flash Fire, not NFPA 2112. Why? Because NFPA 2112 is a minimum performance standard that must be met for a garment to legitimately be represented as being “flame resistant” for use by industrial personnel against flash fire. It does not attempt to provide any guidance on matching the PPE to the quantified hazard — that is what NFPA 2113 is designed for. A few aspects of NFPA 2112 need to be examined in more detail to understand why this is an issue.

Three-second exposure

Much of the confusion with the selection of the appropriate standard comes from the instrumented mannequin garment testing identified in NFPA 2112. Here, a three-second flame engulfment exposure is specified2 using a propane jet-fire heat source that delivers a 2 cal/cm2s [84 kW/m2] heat flux for a total exposure of 6 cal/cm2 [16.8 J/cm2]. This testing condition is based on industrial and U.S. military historical experience for comparing the performance of FR PPE3. Unless the workplace exposure hazard is propane vapor at a similar flow rate and exposure profile, workers could experience heat flux very different than that used in the testing. Jet fires, pool fires and even “flash” (vapor cloud) fires can subject a worker to substantially more heat flux than 2 cal/cm2s [84 kW/m2]4. Materials such as solid propellants and organic solvents can have higher or lower heat flux rates than propane. The fuel material, quantities available, pressures they are under, and escape routes must all be considered to begin to understand the exposure scenarios that may exist in a particular work environment.

What’s worse is the misguided notion that all industrial fires are three seconds or less. Industrial fires happen on average more than once a day in North America and a short duration fire is a rare exception. Open the newspaper, turn on the TV, or visit web sites such as the U.S. Chemical Safety Board (www.csb.gov) to see firsthand evidence of just how extensive fires usually are when they occur at manufacturing, chemical and petroleum-based industrial sites. Three seconds is a performance specification that is only used to qualify a garment as FR. It has nothing to do with establishing the correct level of PPE workers need in your particular fire hazard environment.

50-percent body burn

The next issue to examine in NFPA 2112 is burn injury. For a garment to pass NFPA 2112 testing, it must exhibit a 50 percent or less total predicted body burn using a standardized burn injury model. This burn injury value cannot be directly related to an actual burn injury a person might expect to receive in a fire. It is simply a tool to allow the performance comparisons of one protective garment to another. Fortunately, many years of industrial and U.S. military experience shows that it is a useful predictor for actual performance. So here’s the hard question: Is a garment that generates a 50-percent predicted body burn from a standardized model acceptable to your organization? If not, then you need to look beyond NFPA 2112 compliance and evaluate garment systems for their actual performance levels and not simply a pass/fail criteria based on the 50-percent predicted skin burn injury model.

NFPA 2113

These are only some aspects of worker protection not addressed when specifying NFPA 2112 garments, and this is where NFPA 2113 comes in.

Under NFPA 2113, a hazard assessment must be conducted that will deliver a quantified energy level for the various tasks that workers perform. To properly conduct this hazard assessment, following are some items you should include:

  • Fuel source. What material(s) are burning?
  • Quantities available, pressures they are under, geographic and environmental factors. How much air is available to mix with the fuel to support combustion?
  • Worker reaction time. How long does it take for a person to first identify the fact that they are in trouble and then to do something about it? How many seconds could someone be in a flame rich environment before reaching safety?
  • Worker environment. Are they wearing a fall protection harness, in a confined space, on a catwalk or gantry, in an excavation, etc.?
  • Other gear. Are workers wearing gear that can slow them down or impede their escape?

 

In addition to NFPA 2113, other tools and resources can help address the hazard assessment. The American Institute of Chemical Engineers’ Center for Chemical Process Safety (CCPS) has a variety of publications that provide supplemental questions, analysis strategies, and worked examples.5

In summary, protection from industrial fire hazards must be treated with the same degree of focus and professionalism as any other workplace hazard — the hazard must be identified and quantified, and the appropriate engineering controls, operational SOP, or PPE must be put in place. Just because a garment carries an NFPA 2112 “pass” rating does not necessarily mean it will protect your workers adequately or meet applicable OSHA regulations. There are no shortcuts — do the homework, generate the data, and work with garment providers to understand what type of garments or garment systems will provide the levels of protection required.

 

References

1 The Occupational Safety and Health Act of 1970, and the regulations cited in 29 CFR 1910

1 See for example OSHA Standard Interpretations 03/07/2006 - Requirement for flame-resistant clothing in petrochemical plant covered by PSM.

2 Following ASTM International F1930 Standard Test Method for Evaluation of Flame Resistant Clothing for Protection Against Fire Simulations Using an Instrumented Manikin

3 Historically, the heatflux value represents the approximate energy delivery rate measured by the U.S. Air Force for a typical JP-4 jet fuel pool fire. The three (3) second exposure time represents an approximate minimum escape time, or in the case of the JP-4 pool fire, the time to transit the pool.

4 Large, open hydrocarbon pool fires have been observed to have heat fluxes in excess of 2.9 cal/cm2s [120 kW/m2], jet fires in excess of 5.3 cal/cm2s [220 kW/m2], and vapor cloud fires in excess of 3.3 cal/cm2s [140 kW/m2] for durations > 16 seconds. See the SFPE Handbook of Fire Protection Engineering, Fourth Edition, National Fire Protection Association, 2008, Chapt. 10 for additional information.

5 See for example “Guidelines for Hazard Evaluation Procedures with Worked Examples”, 2nd Ed., 1992, AIChE-CCPS

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