All fires are in reality small hazardous materials incidents. It comes as no surprise that the increasing use of chemicals combined with the complex materials used in building construction create a fairly toxic cocktail when these substances are burned under uncontrolled conditions in a structural fire. The emission of toxic plumes is not limited to facilities that manufacture or use chemicals – most fires evolve a large variety of toxins, carcinogens, and highly hazardous substances.
Numerous studies have characterized the types of contaminants that are commonly encountered at structural fires. As would be expected, there are a number of fire gases. Some examples of fire combustion products include:
- • inorganic gases (hydrogen sulfide, hydrogen cyanide, nitrogen oxides)
• acid gases (hydrochloric acid, sulfuric acid, nitric acid)
• organic acids (formic acid, acetic acid)
• aldehydes
• chlorinated compounds (carbon tetrachloride and vinyl chloride)
• hydrocarbons (benzene)
• polynuclear aromatic compounds (PANs)
• metals (cadmium, chromium)
In addition, chemicals at the site of a fire further contribute to hazardous contaminants in fire smoke. A classic example are polychlorinated biphenyls (PCBs), found in electrical transformers and other equipment, which when burned may form dioxin, an acutely deadly substance. Even the normal household will contain cleaning supplies, pesticides, pool chlorine and other substances which contribute to release of toxic substances at fires.
These chemicals can enter the body through inhalation, ingestion, and skin adsorption. The widespread use of positive pressure, open circuit, self-contained breathing apparatus (SCBA) helps eliminate the most respiratory exposures while SCBA facepiece keeps contaminants from being accidentally ingested. However, the primary means for preventing skin absorption comes from wearing protective clothing that provides barriers to fireground contaminants.
Contact of these chemicals with fire fighting clothing can both penetrate and permeate protective fabrics. Since most firefighter protective clothing uses porous fabrics, the chemical vapors or liquids simply penetrate or pass through the pores of the material. Molecules of chemicals can also permeate into the fibers or coatings of clothing materials and can remain in the material for long periods of time, depending on the types of exposure chemical(s) and care given to the clothing. Chemicals that get into the clothing from either means can directly contact the wearer’s skin.
The likelihood of chemical contact with the firefighter’s skin depends on the state of the contaminant, the amount of contaminant present, the length of contact. Generally, gases and volatile chemicals will quickly desorb from clothing. The one exception is that some gases can be trapped in soot particles and the soot in turn becomes trapped in the clothing retaining the hazardous chemicals. Moreover, less volatile chemicals are likely to remain in clothing, particularly those that are that are not water soluble. It goes without saying that the higher the concentration, or the longer the exposure time, the more likely chemical will be retained in clothing.
Fire departments are commonly faced with the dilemma of trying to determine if their protective clothing has been contaminated. Alternatively, they want to know that clothing has been properly cleaned to ensure that it is safe to wear following a response where contamination is suspected. Unfortunately, the very best way of making this determination can only be accomplished by destructive testing.
Testing clothing for chemical contaminants may seem straightforward, but in reality it can be very complicated. Procedures for conducting this testing can be found in NFPA 1851, Standard on the Selection, Care, and Maintenance of Protective Ensembles for Structural Fire Fighting and Proximity Fire Fighting. Appendix paragraph A.7.1.4.2 offers specific guidance for conducting tests to ascertain the contamination levels in exposed fire fighter clothing using sophisticated analytical techniques.
In order to apply these tests, samples must be removed from clothing. These samples should be taken from the most contaminated portions of the clothing and must be several square inches in size to accommodate common contaminant tests. Further a decision must be made whether to test the contaminated clothing before or after it has been cleaned. The latter will provide information if the contamination is still present, but gives no idea how much contamination was present in the first place. Either way, the clothing must be cleaned before it can be reused, if it is determined to be safe for reuse.
If the contaminant(s) are known, then specific analyses can be run to determine the concentrations present. If the type of contaminants are not known, then it becomes a more difficult analytical problem and the clothing sample must be screened for a wide range of possible chemicals. Typically, chemical screens are for semi-volatile chemicals and inorganic metals. Techniques can be applied that will list any contaminant that is identified.
NFPA 1851 also points out that it is useful to utilize “control” samples, garment materials that have sustained the same general use and that have been cleaned, but representative of garments that have not been contaminated. The purpose of controls is because everyday clothing contains different chemicals that include, but are not limited to, fabric additives and finishes, detergent residue, and other substances that might be contacted routinely. While the analytical techniques can identify contaminants, it important to “subtract” out the ordinary chemicals found in clothing so they do not interfere with the analysis of contaminated clothing.
Even with the use of controls, hundreds of different chemicals can be identified in a clothing material, generally at very low levels (parts per billion). It is difficult to establish clear findings in this kind of analysis when the clothing contaminant is not known. If there is an obvious source of contamination, then it is possible to specifically target that contaminant and then determine if any remains in the clothing. If unknown, a large number of compounds can be identified, but the key challenge is to determine the relevance of any identified chemical contamination. For example, phthalates are common plasticizers and typically show in the analysis of contaminated firefighter protective clothing. These plasticizers arise both from their use in common structural materials as well as from the clothing itself (for example, I would expect some plasticizer use in certain components of the clothing like trim).
Another issue is determining if a chemical is present at a significant concentration to warrant concern. Even when a chemical is detected at a certain concentration, there are few tools that are available to judge potential harm. Unlike respiratory exposure where there are numerous measures of tabulated permissible exposure, there are no specific acceptable levels for concentrations of chemicals as surface contaminants. This poses the question of “how clean is clean?” Certainly, the complete absence of a dangerous contaminant serves as an indication of “clean” garments, but if the contaminant is still present at a very low level, saw parts per billion for a particular chemical, it might not represent any extraordinary hazard to the wearer.
Ideally, it should be the goal of the department to have clothing that is free from any level of contamination. Therefore, if significant contamination is suspected, then clothing should be removed from service and treated as being hazardous until a determination can be made that the clothing will be decontaminated, tested, or retired. These decisions require person with expert knowledge in hazardous chemicals. These persons may be part of a local hazardous materials team or a qualified industrial hygienist (a source for some industrial hygienists can be obtained from the American Industrial Hygiene Association). Otherwise, contact the manufacturer for a recommendation for someone who may help you.
