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: 

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.

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:

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.  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.

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:

How can it be determined that a garment meets appropriate performance criteria? Three NFPA standards address individual aspects of CR/FR protection: 

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.

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.    Send feedback to .