Chemical Protection on the Fireground
By Jeffrey O. and Grace G. Stull
AP Photo/Ed Andrieski
Denver firefighters help a HazMat team with their gear at a State office building that was evacuated after an anthrax scare on Sept. 25, 2006.
Unfortunately, chemical incidents are not always cleanly distinguished from other emergencies. What may start out as a routine response may later become a hazardous materials incident. In fact, many in the fire service now believe that most structural fires are, in fact, mini-HazMat incidents. Given the large volume of synthetic products, liquid chemicals and other hazardous materials found at most fire scenes, there is no doubt that a substantial potential for chemical exposure exists.
Responding departments at every emergency must consider whether hazardous materials exposures will occur and the appropriate PPE to be used. In some cases, standard operating procedures adopted by the organization will dictate guidelines for the on-scene leader to use in making this decision. Clearly, when there has been a spill of a known hazardous substance or if the response takes place at a chemical facility where there is no fire, these decisions can be relatively easy. Nevertheless, many of the industry guidelines for response to chemical incidents indicate the suitability of structural firefighting protective clothing for some hazardous materials incidents depending on the chemical. For example, the DOT Emergency Response Guidebook lists turnout clothing with SCBA as appropriate PPE for several chemicals. The same information can be found in many material safety data sheets (MSDS).
In order for fire departments to understand just what limitations structural clothing has with respect to chemical protection, it is essential to know how this clothing would perform in a structural firefighting environment, or other emergency involving potential chemical exposure. To be clear, the scope of the governing standard – NFPA 1971 – does not address chemical protection. However, a number of requirements that were introduced into the Standard during the 1997 edition are intended to show limited performance against fireground chemicals and hazardous liquids. These include an overall "shower" type test that demonstrates the integrity of the garment, when properly donned with all closures fastened, against liquid penetration.
There is also a series of liquid chemical penetration resistance tests that are applied to garment moisture barrier materials and seams. As a consequence, modern turnout clothing is designed to limit the inward leakage of hazardous liquid, but departments must beware that this performance extends only to each element of clothing – garments, gloves and footwear. With the exception of the optional CBRN criteria provided in the last edition of the NFPA 1971, clothing interface areas are not addressed in any great detail. This is readily evident in the use of most protective hoods that are comprised of porous knit materials that include no barrier layer, which easily allow liquids to penetrate. Likewise, glove and footwear interfaces are not evaluated as part of the standard.
The liquid barrier criteria in NFPA 1971 were put into the Standard to address protection from limited contact with liquids that could be reasonably expected to be found on the fireground. In fact, the chemicals chosen for testing include substances that most firefighters would expect to find – AFFF concentrate, battery acid, gasoline (a mixture of toluene and isooctane is used to represent gasoline), hydraulic fluid, and swimming pool chlorine additive. While these chemicals are hazardous, they are not as dangerous as many of the chemicals that can be found at an emergency scene. Many chemicals can easily vaporize and become toxic to the wearer through skin absorption. NFPA 1971 barrier requirements exist to keep hazardous liquids off the skin by showing that clothing materials, seams and the overall design will retard and prevent liquid penetration. Of course, the testing does not assume absolute worst case exposure but is more representative of splashes and prolonged direct contact with liquids.
A key point in positioning turnout clothing capabilities is recognizing that the protected exposures are from liquids, but not all liquids and other forms that hazardous substances might take. For example, some liquids can be highly hazardous. A case in point is hydrofluoric acid, which has the unusual attribute of penetrating skin and destroying bone mass. Other chemicals, such as acrylonitrile, can cause acute health reactions when prolonged exposure occurs (acrylonitrile has a particular affinity for absorbing into and staying in leather products).
So, it is important to realize that structural firefighting protective clothing is not appropriate around many hazardous chemicals. Certainly, one consideration is the relative amount of chemical present and the likelihood for firefighter exposure. The second equally important factor is how dangerous the chemical or substance is for skin contact and exposure. Chemicals are dangerous when they produce toxic or corrosive effects, or are known carcinogens. As indicated before, there are some hazardous chemicals that are dangerous, but may have little effect on the skin; a very diluted solution of an inorganic salt would be an example of this situation.
Structural firefighting clothing is not gas tight and will not prevent gases or vapors from reaching the skin. This raises several critical issues in deciding the suitability of turnout clothing in some incidents. After all, structural fires produce highly toxic gases and particles. Firefighters rely on the self-contained breathing apparatus to protect their respiratory system from inhalation of these poisons. Yet, fire gases and soot penetrate into clothing and contact or deposit onto skin, respectively. Therefore, gases such as ammonia or chlorine will pass through clothing materials. Moreover, many liquids produce vapors, depending on how volatile the chemicals are and the temperature to which they are exposed. The majority of these vapors will also reach the fire fighter’s skin if turnout clothing is worn.
So how do departments gauge the suitability of turnout clothing against gases and vapors? Once again, it is important to determine if the chemicals involved are skin toxic. If any reference reports that significant health effects can occur through skin absorption, then the department can assume that unacceptable exposure will occur using turnout clothing. The other factor is the relative amount of chemical present, most notably its concentration in air. Most occupational exposure limits are set for respiratory protection, but in the absence of other information, these limits can be applied with a large safety factor for skin exposure. For liquids that produce vapors, it is important to account for how volatile the chemical is and whether the environment will result in increased evaporation and confinement of chemicals. Chemical vapors that are heavier than air will tend to collect in low lying areas, resulting in highly concentrated chemical areas.
Most of the time, the responding units do not know the identity or concentration of hazardous substances they encounter. If there is any doubt, the department must assume that a response in turnout clothing places its members in danger unless otherwise demonstrated. The general SOP is to call the available HazMat team, isolate the area, and put together a response based on better information as it becomes available. There are too many circumstances where turnout clothing is used and firefighters experience acute or chronic health issues following the event. The incidence of elevated cancer has been shown in firefighters compared with many other occupations.
Structural firefighting protective clothing does provide limited protection against chemicals, but this protection is subject to very specific considerations as described above. The direction of protective clothing development in requirements set by NFPA 1971 has taken into account the need for some hazardous material protection in many fireground emergencies, but turnout clothing will only provide this protection for some substances, under some circumstances. Departments that are able to recognize the limitations in turnout gear are in better position to ensure the health and safety of their members.