Today’s fire investigators face increasingly dangerous environments while conducting fire scene investigations because of the widespread use of building materials and furnishings manufactured from plastics, foams, and polymers. These synthetic materials represent fuel loads that produce highly toxic by-products of combustion that may cause personal injuries, illnesses, and occupational diseases unless adequate protective measures are implemented. Most investigators readily recognize the perils at hazardous-materials incidents and fire/explosion dangers at clandestine drug laboratories. However, this same respect and recognition does not extend to residential and commercial structure fires, which can be equally as hazardous.

A house fire may not involve large quantities of hazardous materials and other health and safety concerns commonly found in many commercial and industrial occupancies, but various hidden dangers injure or kill investigators just as easily.

(1) Investigators may be inadvertently exposed to numerous insidious toxic substances that may cause serious chronic illnesses days, months, or years after exposure. (Photos by author.)


For example, a chief in California arrived on the scene of a residential fire and walked through the structure to assess the damage. A short time later, as he was returning to the fire station, he became ill and his aide transported him to a local hospital. The haz mat response team was called to the scene and located several glass containers of a substance later identified as liquid sodium cyanide. The chief was subsequently transported to a medical facility equipped with a hyperbaric chamber for treatment and fully recovered. Physicians and investigators eventually determined that he had inhaled near-lethal doses of sodium cyanide from a jewelry/precious metal refinishing business that was operated from the home.

In another incident, eight firefighters and a civilian were injured in a residential fire that involved a dozen 55-gallon drums containing such chemicals such as epoxy resins, acetone, benzene, and toluene in an attached garage. These toxic chemicals were used in a family-owned seamless floor covering business run from the home.1

Fire investigators also face similar hazards from the proliferation of clandestine drug laboratories operating in homes, hotel rooms, warehouses, mobile homes, vehicles, apartments, sheds, and storage units. Many “clan labs” operate undetected until fires and explosions expose their existence and fire and police officials are notified. The clandestine manufacture and production of methamphetamine typically requires the use of extremely volatile, flammable, and toxic chemicals including sodium metal, sodium hydroxide, hydrogen chloride, ether, freon, anhydrous ammonia, hydriodic acid, red phosphorous, and phosphine gas. Some of these chemicals are severe respiratory hazards; some may be water-reactive and corrosive and may form hypergolic mixtures that are highly flammable. Investigators may inadvertently come in contact with these chemicals while conducting origin-and-cause examinations unless they follow strict safety precautions.

The safety and health of investigators are often taken for granted, since most investigators assume that by the time they arrive at a fire scene, the potential safety and health hazards are either eliminated or diminished to the point that they are no longer a concern. Although many experts in the field readily acknowledge that fire scenes are inherently dangerous, these same experts cannot state with any degree of reasonable certainty the appropriate level of personal protective clothing and equipment (PPE) investigators should wear at such scenes. Although common sense dictates that wearing some type of basic personal protective clothing and respiratory protection is probably a good idea, the specific types and their effectiveness have yet to be determined.

For whatever reason, most of the organizations representing the interests of most fire and explosion investigators in this country have not taken the lead in promoting the safety and health of investigators, and most have only paid it lip service. Most organizations have yet to understand that conducting fire scene investigations is inherently dangerous and may cause disabling and debilitating injuries and chronic illnesses that may surface days, months, or years after fire scene investigations have been completed and investigators have retired to enjoy the “good life.”

For years, the mindset of fire investigators has been to respond to a fire scene to conduct a fire scene examination as quickly as possible, oftentimes as the fire department is still performing suppression or overhaul operations. There are several important reasons for this: scene security, evidence preservation, and the importance of interviewing witnesses to obtain key information before they leave the scene. This mindset is continuously reinforced countless times through fire investigation training and education programs. Responding to fire scenes as quickly as possible is certainly an essential investigative tenet, particularly where arson is suspected. However, it also happens to be the time when investigators are the most vulnerable to injury and exposure to hazardous atmospheres and conditions.

The irony of this scenario is that most fire investigators who rose up through the ranks of the fire service and routinely wore structural firefighting protective clothing and respiratory protection while performing suppression and overhaul do not give much consideration to wearing respiratory protection and personal (chemical) protective clothing when they assume the role of fire investigators. Why has this attitude and behavior become the norm?

In many organizations, investigators are working in cultures of the past in which it is perfectly acceptable to spend hours digging out a fire scene without wearing any PPE other than coveralls, a helmet, boots, and gloves. There are also many “lone wolves” roaming around fire scenes who refuse to take any precautions to protect themselves because “that’s the way it has always been done.” Since they haven’t been injured or killed so far, “what’s the big deal?” This attitude is inherently dangerous and will eventually injure or kill someone unless a new awareness, appreciation, and approach are adopted.

(2) Virtually all fire scenes contain numerous toxic by-products of combustion, several of which are known or suspected carcinogens.


Wearing basic protective equipment such as chemical-resistant coveralls, gloves, helmet, eye protection, boots, and adequate respiratory protection may help prevent injury, exposure, illness, and death. Over the past decade, several studies of firefighter occupational safety and health hazards associated with fire scene overhaul operations conducted in Canada, the United Kingdom, New Zealand, and the United States have documented the presence of numerous toxic by-products of combustion, several of which are known or suspected human carcinogens, such as acrolein, acrylonitrile, benzene, formaldehyde, and vinyl chloride. These studies also noted that exposure to these toxicological hazards may result in increased incidence of cancers of the brain, lung, kidney, bladder, and liver. Firefighters working in these environments routinely wear structural firefighting protective ensembles including respiratory protection equipment to prevent exposure. However, most fire investigators seldom think to wear a similar protective ensemble even though they often enter scenes during or shortly after overhaul is completed.

The inhalation of harmful dusts, toxic gases, and vapors at fire scenes is a common hazard to investigators who typically arrive to initiate their investigation after fire suppression operations are completed. In these situations, adequate respiratory protection is critical to avoid exposure and potential short- and long-term adverse health effects. Fire scenes often contain harmful by-products of combustion such as those listed above and also aldehydes; formaldehyde; hydrogen chloride; polynuclear aromatic hydrocarbons; volatile organic compounds; respirable dust; hydrogen cyanide; carbon monoxide, nitrogen dioxide, sulfur dioxide; and asbestos. Some of these substances have been classified as known or potential human carcinogens by the International Agency for Research on Cancer (IARC) and the U.S. Environmental Protection Agency (EPA). If we step back and focus on this issue for a moment from a “commonsense” perspective, we can easily see that standing, kneeling, or crawling around fire scenes for 20 years inhaling benzene, formaldehyde, hydrogen chloride, hydrogen cyanide, carbon monoxide, asbestos, and acrolein is probably not the most healthful thing to do.

The next time you decide to enter a fire scene during or after overhaul operations without wearing any type of respiratory protection, or you are tempted to remove your respiratory protection for comfort, consider the following. According to an in-depth study conducted by Robin Rowland of CBC News in Canada, the most dangerous time for personnel working at fire scenes is after the fire is out because potentially toxic levels of smoke, fumes, and soot are still present. The report Deadly Duty, Firefighters Cancer Risk, states that at least 15 studies show a statistical link between brain cancer and firefighting.2

After reviewing the death reports of 6,000 Toronto firefighters, Epidemiologist Kristin Aronson, a specialist in the causes of cancer quoted in the report, identified a myriad of toxic substances created by burning and smoldering plastics that produce potentially cancer-causing vapors. These insidious vapors can be found in smoke from glues, wraps, paints, insulation, and other synthetic building materials found in almost every modern residential and commercial structure. Polyvinyl chloride (PVC) is found in upholstery, wiring, pipes, and wall coverings. When burning, PVC produces hydrogen chloride and phosgene; it can be more dangerous when smoldering than when burning at the height of a fire because during incomplete combustion it emits carbon monoxide, hydrogen cyanide, hydrochloric acid, and other harmful substances.

A 1994 Ontario Industrial Disease Standards Panel Report estimated that 80 percent of firefighters’ injuries result from smoke inhalation or oxygen deficiency and that more than 50 percent of line-of-duty deaths are caused by smoke exposures. The report also noted that firefighters sometimes found self-contained breathing apparatus (SCBA) to be too hot, heavy, and cumbersome under strenuous conditions. Consequently, firefighters often removed their SCBA as soon as the fire was extinguished since they perceived that the danger of exposure to potentially hazardous substances generated by the various toxic by-products of combustion no longer existed.3 In addition to brain cancer and carbon monoxide poisoning, recent research has shown that failure to wear adequate respiratory protection during overhaul and other nonfirefighting operations can lead to severe respiratory problems, including respiratory failure. Regularly working in contaminated environments may also be more threatening to individuals with preexisting heart and lung conditions.

Although these studies specifically targeted firefighters, fire investigators may face similar risks from working at fire scenes for hours, days, weeks, months, and years with inadequate or no PPE. In these situations, the real question that needs to be answered is, Are investigators subject to the same increased incidence of cancer and other serious medical conditions such as heart disease as firefighters? Unfortunately, the answer is “no one really knows for sure” because no comprehensive scientific research studies have been published to date. Therefore, we can only make general assumptions and educated guesses based on evidence derived from studies of fire service personnel, which may or may not be valid for fire investigators.


Safety is both an attitude and a behavior, and personnel need to have the proper mindset to be safe and stay healthy. Organizational safety programs, standard operating procedures, training and education programs, and the best equipment money can buy will not in and of themselves prevent someone from being injured or killed. These key components of a comprehensive safety and health program cannot always control the two most important factors in accident and illness prevention: a person’s attitude and behavior.

According to the most recent Bureau of Labor Statistics (BLS) Occupational Injury and Illness Data, 90 percent of on-the-job injuries are self-inflicted. The key to safe behavior lies with the proper attitude coupled with proper actions. This philosophy needs to be continuously reinforced in all employees in an organization and supported by all levels of management. Organizations must reinforce the safety mindset through refresher training, continuing education programs, and strict enforcement of safety policies with immediate disciplinary action for noncompliance. One of the most important components of an occupational safety and health program for fire investigators is respiratory protection.

Some fire and law enforcement agencies with no formal written respiratory protection programs as required by Occupational Safety and Health Administration (OSHA) requirements incorrectly assume that low cost, disposable dust-type masks are suitable for investigators to use while processing fire scenes. As was determined during the investigation into the collapse of the World Trade Center, these types of masks offer little or no protection against the majority of harmful substances present in and around the scene. As a result, many first responders involved in the initial response to the incident continue to suffer from a variety of chronic respiratory problems.

Some agencies issue this type of mask because their use is not subject to the requirements of OSHA’s Respiratory Protection Standard (29 CFR 1910.134). However, dust-filtering masks are not considered respiratory protection devices and provide no protection against toxic atmospheres or asphyxiation from oxygen-deficient environments. Inves-tigators working in environments where there is a potential for chemical exposures need respirators designed to adequately protect them in these situations. A respirator equipped with a three-way combination cartridge (organic vapor, particulate, and acid gas) or a positive-pressure SCBA provides a much higher level of protection from toxic or noxious fumes and gases from burning materials. Dust masks also often fail to maintain a tight face-to-face piece seal, therefore allowing harmful contaminants to enter the airway and lungs. In addition, these types of masks offer no protection from potential eye exposures.

A respiratory or breathing hazard exists when a toxic contaminant is present in the air at a sufficient concentration to cause harm when inhaled. The damage may occur immediately, or it may take days, weeks, months, or years for effects to surface. Investigators need to be especially concerned with those atmospheres considered to be immediately dangerous to life and health (IDLH). In an IDLH atmosphere, if a person’s respiratory protection fails, he cannot escape without suffering adverse health effects or serious physical injury. Air that contains insufficient oxygen (less than 19.5 percent) and concentrations of toxic gases such as carbon monoxide and hydrogen cyanide that exceed established permissible exposure limits are considered IDLH environments.

OSHA regulations specifically define what constitutes an IDLH atmosphere and the required level of respiratory protection. If investigators enter fire scenes immediately after overhaul, IDLH conditions could still exist, requiring the use of positive-pressure SCBA. As an alternative, if the area is considered to be IDLH, engineering controls such as proper ventilation may reduce the level of harmful contaminants to a level that can be deemed safe through air monitoring. At that time, the level of respiratory protection can be downgraded. In these instances, investigators are often left with an atmosphere contaminated with particulates and an approved respirator equipped with a high-efficiency particulate air (HEPA) filter can be used. Personnel should remember that the atmosphere determines the level of protection, not the type of task to be performed. According to National Fire Protec-tion Association (NFPA) 921, Guide for Fire and Explosion Investigations, personnel entering fire scenes immediately after fire suppression has been completed should wear SCBA. At “cold” scenes, filter masks with the appropriate cartridges should be worn.

By wearing the appropriate type of respirator, investigators can protect their lungs from numerous inhalation hazards. OSHA regulations require that, if possible, engineering or administrative controls and work practices be used to prevent air contamination at the workplace and reduce employee exposure below the OSHA Permissible Exposure Limits (PEL). However, if these controls are not possible, the employer is required to provide the employee with an appropriate type of respirator.

(3) Investigators should avoid the tendency to “rush in” but should take some time to properly evaluate the potential hazards and risks before entering a fire scene.



Several types of respirators are available, each designed for use in a specific hazardous environment. There are two basic types: air-purifying and air-supplying.

Air-purifying respirators (APRs) only remove harmful contaminants from the air and cannot be used in an oxygen-deficient environment or in any other IDLH atmosphere that may be found at a fire suppression scene or a haz-mat incident.

Air-purifying filters and cartridges have a limited lifespan and must be changed frequently. Chemical cartridges/canisters must be changed before the chemical absorbent is depleted; this should be done under the guidance of a qualified person, such as an industrial hygienist.

Air-supplied respirators provide air from a clean source outside the work area or from a compressed air cylinder. They are used in IDLH environments and for substances with poor warning properties (e.g., odorless and tastless). Examples of air-supplied respirators include airline units and SCBA.

Respirator face pieces come in two forms: full-face and half-face. The full-face mask covers the face from hairline to chin and provides the most reliable fit, as well as eye protection against contaminants that are irritants or corrosives. The half-face covers only from the bridge of the nose to the chin and provides no protection for the eyes unless some type of protective eyewear is worn.


Before selecting a respirator, it is essential to determine what the hazard is and quantify how much is present, if possible. If this is not possible or practical, the highest level of respiratory protection should be donned prior to entering the scene. The organization should conduct a hazard and risk assessment of the workplace in an attempt to characterize the types of environments and associated safety and health hazards. This should be completed prior to the selection, purchase, and issuance of any respiratory protection equipment designed for the specific hazards investigators are likely to encounter.

It is very important to understand the functions and limitations of the specific types of respiratory protection devices that are issued. Selection of respirators should be made according to guidelines established by OSHA, the Mine Safety and Health Administration (MSHA), the National Institute of Occupational Safety and Health (NIOSH), and the NFPA. Selecting the proper respirator is a complicated process. If the wrong type of respirator is chosen, personnel will not receive adequate protection, and the consequences can be serious.

It is important to understand that the degree of respiratory protection varies greatly with the type of respirator and is indicated by the assigned protection factor (APF). The protection factor represents a respirator’s efficiency in removing air contaminants from the individual’s breathing air. The APF is the ratio of contaminant concentration outside the respirator to the concentration inside the respirator. The higher the protection factor, the better the respirator’s efficiency. Protection factors range from 10 for APRs to 10,000 for positive-pressure (SCBA). A list of the protective factors assigned to various respirators can be obtained from OSHA at


Another important factor to consider while wearing a respirator is maintaining a tight fit. A respirator can only protect an individual effectively if there is a good seal between the wearer’s face and the face piece. A gap or poor seal will allow contaminants to leak into the respirator and be inhaled; therefore, respirators that leak should not be worn because of the potential for exposure.

To ensure that respirators fit correctly, fit-testing is essential. It must be performed for each person to provide a style and size that would provide the best fit and the most comfort.

In the qualitative fit-testing method, the respirator wearer is exposed to an irritant smoke or odorous vapor test agent (such as banana oil) for which the respirator must have the proper cartridges. If the wearer does not detect the presence of the agent in the face piece, the fit is considered acceptable.

In quantitative fit-testing, an instrument (e.g., Porta-CountT machine) is employed to specifically measure the integrity of the face-to-face piece seal to ensure that it is adequate. The respirator should also be fit-tested before each use to verify that a good seal exists. OSHA’s Respiratory Protection Standard (29 CFR 1910.134) requires that fit tests be performed annually and anytime new equipment is purchased and issued.

A physician must first examine personnel required to wear a respirator on the job to determine whether they are physically fit. Since wearing a respirator imposes some stress on the user, people with conditions such as chronic bronchitis, emphysema, breathing difficulties, anemia, and heart disease may not be permitted to wear respirators and therefore may be determined unfit for jobs that require them to wear a respirator. Individuals with facial hair such as a beard (or long hair) or who wear an eyeglass temple piece that prevents a direct skin-to-face piece seal also should not be permitted to use respirators.


All respirators must be inspected before and after each use to detect any defect, deterioration, or excessive wear or defective/damaged components. Pay special attention to the face piece, especially the face seal surface, cartridges (or canister), and exhalation valve. Check the tightness of the connections. If you are not familiar with the parts and functions of the respirator, a trained individual should perform the inspection. A properly trained and certified individual should make repairs.

If you have been assigned a respirator for your exclusive use, the respirator must be cleaned regularly, preferably after each use, including training and fit-testing. Respirators used by more than one person must also be thoroughly cleaned after each use. Respirators should be stored in a clean and sanitary location in accordance with the manufacturer’s recommendations. Cartridges or canisters should be stored in sealed plastic bags to prevent absorption of contaminants or moisture.

The replacement intervals depend on the substance to which the individual has been exposed and the length of exposure. As a general rule, when the person begins to have difficulty breathing, it’s time to change the filter/cartridge. Some respirators are equipped with an end-of-service-life indicator (ESLI) that provides a visual indication that the cartridge requires replacement. Air-purifying filters and cartridges have a limited lifespan and must be changed frequently. For additional information concerning OSHA’s respiratory protection requirements, refer to 4

Until definitive scientific data that specifically address the safety and health hazards associated with conducting fire scene investigations and the potential short- and long-term health effects are published, investigators should approach all fire scenes with the same level of caution and respect they would have for hazardous-materials incidents. This mindset will help ensure that personnel take the steps necessary to protect themselves against exposure to toxic substances and potential acute and chronic health effects; these precautions should always include wearing respiratory protection equipment. As the old saying goes, “An ounce of prevention is worth a pound of cure.”


1. Knapp, Jerry and William Lee, “Hidden Hazards of House Fires,” Fire Engineering, November 2003, 93-98.

2. Dittmar, Mary Jane, Health Beat, “The ‘Smoldering’ and ‘Flying’ Hazards, Part I,”, October 2002.

3. McLauchlin, David, and Curt Petrovich, “Investigative Report: Firefighters Cancer Risk,” CBC Radio News; Dr. Brian Goldman, CBC Television News; Robin Rowland & Gary Graves, CBC News Online, safety/, Feb. 5-6, 2001.

4. Additional health-related information on the hazards and short- and long-term health effects associated with firefighting can be obtained at Information on investigator safety and health-related topics can be found in a new book available from Fire Protection Publications (FPP)/International Fire Service Training Association (IFSTA), Safety and Health Guidelines for Fire and Explosion Investiga-tors.

MICHAEL L. DONAHUE, IAAI-CFI, is an International Association of Arson Investigators (IAAI) certified fire investigator (CFI) and a nationally certified hazardous-materials technician. He has 20 years of experience in the fields of fire/arson investigation, occupational safety and health, and law enforcement. Prior to his current assignment in the Department of Justice (DOJ), he was a special agent/criminal investigator with the U.S. Drug Enforcement Administration (DEA) and a police officer with the Rockville (MD) Police Department. He is the author of Safety and Health Guidelines for Fire and Explosion Investigators (first edition), published by Fire Protection Publications/International Fire Service Training Association (FPP/IFSTA), and moderator of, a Web site dedicated to occupational safety and health-related issues for fire and explosion investigators.

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