One of the more difficult challenges for industrial hygienists and safety professionals involves the selection of chemical protective clothing for use when chemical and fire hazards are present at the same time. Such scenarios can include a single substance that is both toxic and flammable or multiple chemicals that share a combination of these hazardous properties. Dual chemical and fire hazards are common to refineries, petrochemical and other chemical plants, and even certain laboratory settings.  The key issue is that each hazard often requires different types of protection, and the protections may not always be compatible. For example, most materials used in traditional chemical-resistant garments are flammable. Some materials can even melt upon exposure to heat. Conversely, most materials used in traditional flame-resistant clothing offer little or no chemical protection. Compounding the problem, if chemical and flammable hazards are present at the same time, a traditional CR garment must not be worn over the top of or underneath a traditional FR suit.
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FIRE HAZARDS When discussing flame resistance regarding fire hazards, it is essential to understand that this involves more than just how a material reacts to an open flame. Flame-resistant materials need to protect users from more serious events, such as flash fires. Flammable and combustible materials are often visualized as burning in an open pool of fire where the energy is released relatively slowly, with the fire lasting for long periods until the fuel supply is consumed. An example of this scenario is release of a flammable or combustible material from an overturned tank truck that ignites and burns, shutting down a highway for hours. However, under the right conditions, an ignitable concentration can be produced and, in the presence of an ignition source, certain materials can explode or flash with an immediate release of energy. Fires started in this manner are commonly referred to as flash fires. Some materials may also flash without an ignition source if the temperature is above its autoignition temperature. Examples of conditions that can lead to a flash fire include the following: 
  • flammable gases released into the atmosphere
  • flammable or combustible liquids being handled above their boiling point or flash point and released into the atmosphere
  • combustible dusts agitated and suspended in the air

Flash fires can be very intense, but they don’t last long—only three to four seconds. But in that short period they can be very damaging and result in severe burns, lung damage from breathing hot gases, and injuries from shrapnel and debris. Exposed skin will be burned by the heat and flame of a flash fire; however, some of the worst burns can be caused by the ignition of common work apparel. Ignition of work clothing is particularly problematic because the clothing burns in direct contact with the skin, will burn away from the point of ignition with increasing flame spread, and will continue to burn until extinguished or consumed as a fuel source. Typically, the clothing can burn for a much longer period of time than the initial flash fire. The solution to ignitable work clothing is the use of FR clothing, which is work clothing or outerwear that provides protection against clothing ignition and sustained flame spread, will self-extinguish almost immediately after removal of the ignition source, and prevents spread of flames away from the immediate area of high heat impingement.

RISK ASSESSMENT OVERVIEW According to OSHA’s standard for personal protective equipment (29 CFR 1910.132), OSHA expects employers to assess the workplace to determine if hazards are present that require the use of personal protective equipment. If such hazards are present or likely to be present, the employer must select PPE that will protect the affected employees from the hazards. Hazard risk assessments should always consider the likelihood of chemicals igniting or otherwise reacting when personnel are present. A hazard risk assessment should answer the following questions:

  1. What is the task or operation to be performed?
  2. What substances are involved?
  3. What is the physical state of the substances?
  4. How is each substance a hazard?
The last question is used to establish whether a chemical hazard or a flammable hazard, or both, are present. The key considerations for establishing the presence of a flammable hazard include the flammability of the material (as indicated by its National Fire Protection Association flammability rating), its boiling point, its flash point, and its autoignition temperature. The environmental or process conditions must also be considered, such as temperature, pressure, and the presence of oxidizers, which can widen the flammable range and lower the BP, FP, or autoignition temperature. Depending on the results of the initial screening, a more detailed evaluation may be required. Table 1 offers guidance for evaluating the flash fire risk for liquids, vapors, and gases.
Table 1. Flash Fire Initial Screening Guidance for Liquids, Vapors, and Gases
Tap on the table to open a larger version in your browser.
CHEMICAL HAZARDS AND PROTECTIVE CLOTHING SELECTION In addition to answering the questions asked during a hazard risk assessment, two sets of additional questions need to be answered to select appropriate CPC:

  1. What is the result of the substance’s contact with the skin? What is the chemical action on the skin? Is the substance dermally absorbed and toxic systemically? How toxic is the substance? 
  2. What is the potential exposure to the substance? What is the likelihood of contact with the substance? If contacted, what is the amount, the duration, and the direction of contact?
Once the CR/FR exposure scenario has been defined, then the CPC selection process can proceed. The next step should be to identify an appropriate garment design. For example, is a fully encapsulating suit, a hooded coverall, the partial body coverage of an apron, or some other design needed? Next, identify an appropriate seam type and closure system. Then determine a suitable material or fabric for the CPC.  The garment material/fabric must provide an effective barrier for the specific chemicals identified in the exposure scenario. Chemical barriers can be assessed in three ways: degradation, penetration, and permeation. Degradation is the physical change in one or more properties of the material due to exposure to a chemical—for instance, swelling or cracking. Penetration involves the bulk flow of a chemical through voids in the material matrix, such as gaps, pores, holes, imperfections, and seams. Permeation, on the other hand, is the process by which a chemical migrates through the material matrix on a molecular level by absorbing at the point of contact, diffusing through the material, and desorbing from the opposite surface.  The American Society for Testing and Materials and the International Organization for Standardization have developed test methods to assess all three barrier properties. However, note that some chemicals may pass the penetration test but fail the permeation test. Permeation is a better measure of chemical barrier protection than penetration. Degradation tests are important in the garment selection process because product failure may result if the chemicals are incompatible with the clothing material.  FR SELECTION When determining the appropriate level of FR protection, identify whether “primary” or “secondary” FR protection is needed. Primary FR garments can be worn alone to protect against burn injuries. Daily-wear work uniforms such as FR fabric-type Nomex coveralls are one example of primary FR garments. Secondary FR garments are meant to be worn over primary FR garments to keep the primary FR garment clean or to protect the wearer from another hazard, such as a chemical, in which case chemical- resistant protection is needed. Refer to the decision tree in Figure 1 for selection assistance when determining whether CR, FR, or combination CR/FR protective clothing is needed.
Figure 1.  Decision tree for selecting CR and FR clothing. Courtesy DowDuPont.
Tap on the figure to open a larger version in your browser.
BENEFITS OF CR/FR Although not within the scope of this article, it is important to recognize that CPC is only one component of a protective ensemble that also includes respiratory, hand, head, and foot protection matched to the CR/FR exposure scenario. So, if CR/FR protective clothing is required, what does that mean, exactly? In the simplest terms, it means the following:

  • The garment will not ignite when exposed to a flame or, if it does ignite, it will quickly self-extinguish once the flame source is removed.
  • The garment will not melt and drip.
  • The garment will remain intact and provide thermal insulation to protect the wearer’s skin to reduce likelihood of thermal burn injury.
  • The garment will remain intact and continue to protect against any remaining chemical hazards.
ASSOCIATED PERFORMANCE STANDARDS How can it be determined that a garment meets appropriate performance criteria? Three NFPA standards address individual aspects of CR/FR protection: 

  • NFPA 1991, Standard on Vapor-Protective Ensembles for Hazardous Materials Emergencies (2016), addresses protection from hazardous chemical gases and vapors, requires a minimum flame resistance level for all covered ensembles, and provides the option for a higher level of flame resistance for escape from flash fires.
  • NFPA 1992, Standard on Liquid Splash-Protective Ensembles and Clothing for Hazardous Materials Emergencies (2012), addresses protection from hazardous chemical liquids and provides the option for a higher level of flame resistance for escape from flash fires.
  • NFPA 2112, Standard on Flame-Resistant Garments for Protection of Industrial Personnel Against Flash Fire (2012), specifies minimum performance requirements for flame-resistant fabrics and components, and specifies the design and certification requirements for garments to be used in areas at risk from flash fires.
These NFPA standards mainly deal with assessing primary FR levels of performance. When worn alone, primary FR garments are designed to reduce burn injury and increase the wearer’s chances of survival. They are intended to provide escape time from an unintended fire exposure and should not be used to enter a burning area. Secondary FR garments are typically chosen for task-specific operations when traditional primary FR garments are worn. Secondary FR garments should “do no harm” if a flame exposure occurs. In addition, secondary FR garments must not be worn alone or over everyday clothing if FR protective clothing is required based on the hazard analysis.  Refer to Figure 2 for an overview of available CR, FR, and combination CR/FR garment options.
Figure 2. Available CR, FR, and CR/FR garment options. Courtesy DowDuPont.
Tap on the figure to open a larger version in your browser.
The options for combination, all-in-one CR/FR garments are currently limited. Several CPC manufacturers offer NFPA 1991-certified Level A suits with the flash fire escape option. However, only one combination NFPA 1992/NFPA 2112-certified garment is available on the North American market today, the DuPont Protection Solutions Tychem 6000 FR, a Level B/C garment available as a hooded coverall. The same garment is available worldwide. The alternative is use of a secondary FR chemical garment (SFR/CR) over a primary FR garment. A combination SFR/CR could be an acceptable choice if it provides an effective barrier against the specific chemical hazards present, it will quickly self-extinguish once the flame source is removed, and it does not melt and drip. Several options for combination SFR/CR garments are available on the North American market today.    CURTIS HINTZ, CIH, CSP, is industrial hygiene manager at DowDuPont and a member of AIHA’s Protective Clothing and Equipment Committee. He can be reached via email. MARK TARTAGLIA, MSPH, CIH, is the senior certified industrial hygienist supporting the DuPont Protection Solutions business of DowDuPont and a member of AIHA’s Protective Clothing and Equipment Committee. He can be reached via email. Send feedback to The Synergist.

Dual Hazard Protection
Selecting Protective Garments for Both Chemical Resistance and Flame Resistance 
BY CURTIS HINTZ AND MARK TARTAGLIA
Photo courtesy DowDuPont. The worker in the image is wearing the DuPont Tychem 6000, a single-hazard, chemical-resistant garment (non-FR version). View images of Tychem® 6000 FR.
Although the print version of The Synergist indicated The IAQ Investigator's Guide, 3rd edition, was already published, it isn't quite ready yet. We will be sure to let readers know when the Guide is available for purchase in the AIHA Marketplace.
 
My apologies for the error.
 
- Ed Rutkowski, Synergist editor
Disadvantages of being unacclimatized:
  • Readily show signs of heat stress when exposed to hot environments.
  • Difficulty replacing all of the water lost in sweat.
  • Failure to replace the water lost will slow or prevent acclimatization.
Benefits of acclimatization:
  • Increased sweating efficiency (earlier onset of sweating, greater sweat production, and reduced electrolyte loss in sweat).
  • Stabilization of the circulation.
  • Work is performed with lower core temperature and heart rate.
  • Increased skin blood flow at a given core temperature.
Acclimatization plan:
  • Gradually increase exposure time in hot environmental conditions over a period of 7 to 14 days.
  • For new workers, the schedule should be no more than 20% of the usual duration of work in the hot environment on day 1 and a no more than 20% increase on each additional day.
  • For workers who have had previous experience with the job, the acclimatization regimen should be no more than 50% of the usual duration of work in the hot environment on day 1, 60% on day 2, 80% on day 3, and 100% on day 4.
  • The time required for non–physically fit individuals to develop acclimatization is about 50% greater than for the physically fit.
Level of acclimatization:
  • Relative to the initial level of physical fitness and the total heat stress experienced by the individual.
Maintaining acclimatization:
  • Can be maintained for a few days of non-heat exposure.
  • Absence from work in the heat for a week or more results in a significant loss in the beneficial adaptations leading to an increase likelihood of acute dehydration, illness, or fatigue.
  • Can be regained in 2 to 3 days upon return to a hot job.
  • Appears to be better maintained by those who are physically fit.
  • Seasonal shifts in temperatures may result in difficulties.
  • Working in hot, humid environments provides adaptive benefits that also apply in hot, desert environments, and vice versa.
  • Air conditioning will not affect acclimatization.
Acclimatization in Workers