For over a decade the world health community has been researching the health effects of vehicle exhaust emissions produced by internal combustion engines. The conclusion is that long and even short-term exposure to diesel, gas and compressed natural gas (CNG) can cause cancer in humans.

The exhaust from all internal combustion engines, including diesel and gasoline-powered engines, contains over 100 individual hazardous chemical components that when combined, can result in as many as 10,000 chemical compounds. A large majority of these compounds are listed by state and federal regulatory agencies as being cancer causing or suspected carcinogens.


What are the hazards?

There are many published reports that identify diesel exhaust fumes as carcinogenic, and not just a noxious fume, and therefore a health issue that must be addressed. There are also published reports on the different methods to remove diesel fume from the Fire Station. Over the past twenty years there has been a considerable interest in the potential adverse health effects from exposure to diesel engine emissions. In considering the potential health effects arising from exposure to diesel exhaust, it is helpful to view the exhaust as being composed of two phases, gaseous and particulate. The gaseous phase of diesel exhaust is composed of carbon monoxides, oxides of sulfur and nitrogen and unburned and partially burned hydrocarbons.

Diesel engines also emit particulates, in an amount 50 to 80 times greater than gasoline powered vehicles. These particulates are small in size, easily inhaled and they contain a myriad of different chemicals adsorbed on their surfaces, which typically represent 15-65% of the mass of the particles.

There are many published reports on the subject of diesel exhaust and suggested actions in order to eliminate exposure to these emissions. Highlights of these reports are as follows:

Diesel Exhaust Hazards, The Windsor Occupational Safety & Health Council, describes the compounds found in diesel exhaust fumes. The main concerns discussed are the Polynuclear Aromatic Hydrocarbons (PAH) and benzo (a) pyrene (BaP) a known and powerful carcinogen. The report states, “The only exposure to a carcinogen is no exposure at all.”

NIOSH Pocket Guide to Chemical Hazards, U.S. Department of Health and Human Services, National Institute for Occupational Safety and Health, now classifies diesel exhaust in a separate category listed as NIOSH Potential Occupational Carcinogen. Appendix A states “occupational exposure to carcinogens be limited to the lowest feasible concentration. To ensure maximum protection from carcinogens through the use of respirator protection (such as an SCBA).

Benzene in Diesel Exhaust Increases Firefighters Cancer Risk, Gary Girod, instructor in Hazardous Materials for the California Fire Academy and University of California at Santa Barbara, states that “the active firefighter, responding with diesel apparatus, on 4 to 6 calls per shift, may increase the danger of lung cancer by 200%”. To limit exposure he lists 8 steps, of which:

  • Item #2 is positive pressure the living quarters.”
  • Item #3 is provide an exhaust system connected to the tailpipe.

Girod also says, “By far, the most positive approach the reducing diesel exhaust exposure is the specially designed, fan assisted exhaust removal system (Source Capture System). Chronic Exposure is not worth taking the risk.”

NFPA 1500 Handbook, Paragraph 7-1.5 requires that the fire station be designed and provided with means to ventilate exhaust emissions from the fire apparatus to prevent exposure to fire fighters and contamination of living and sleeping areas. It also states:

  • “that the carcinogenic effect of diesel exhaust is present even if the particulates (soot) are filtered out of the exhaust.”
  • “the most effective means is to connect a hose that ventilates exhaust to the outside to the exhaust pipe of all vehicles.”

Diesel Exhaust in Fire Stations, Information Bulletin, New Jersey Department of Health, identifies Polynuclear Aromatic Hydrocarbons (PAH) and benzo (a) pyrene (BaP) as compounds of potential toxicological significance.

New York City Report of five fire stations evaluated by Mine Safety Appliances (MSA) Research Corporation. Four methods of removing diesel fumes from the fire stations were tested.

  • Exhaust fans that provided twelve (12) air changes per hour were found to be ineffective.
  • Ceramic Filters installed in the diesel exhaust air stream removed particulates but did not address the gaseous emissions. The filter element needed to be removed from the vehicle for regeneration servicing.
  • Implementation of a more rigorous preventative maintenance schedule had only minimal improvements.
  • Source Capture with flex hose attached to the tailpipe was the only method to consider.

Health Assessment Document for Diesel Emissions, Volume I of II , section Atmospheric Transformations of Primary Diesel Emissions by the United States Environmental Protection Agency (EPA). Some of the main points are:

  • “primary diesel emissions are a complex mixture containing thousands of organic and inorganic constituents in the gas and particulate phase.”
  • Figure 3-2. shows the Polycyclic Aromatic Hydrocarbon (PAH ) distribution as a percentage of particles and vapor (gas). On an average, 75% of the PAH diesel fume is in a gas form.
  • Table 3-9. shows Benzene (which is a gas) still present after 18 days.

Source Capture As The Recommended Method To Control Diesel Exhaust Emissions At the Fire Station, Jeffrey O. Stull, International Personnel Protection, Inc. states in his report that “diesel exhaust can penetrate into and absorb onto clothing, furniture and other items which fire fighters have routine contact, where it can be later released after initial exposure or absorb into the fire fighters’ skin.” On the discussion of available solutions, listed are:

  • After market diesel exhaust filters added to the apparatus exhaust system may appear to clean exhaust by removing visible particulates, but still allow hazardous gases to pass through and remain within the fire station.
  • General ventilation has several disadvantages:
    • Does not guarantee removal of all diesel exhaust because of dead air space within the station.
    • The rate of air exchange within the apparatus bay does not always keep pace with the generation rate.
    • No precautions in place to know when the system is not performing as designed.
    • Does not keep diesel fume from absorbing into clothing and equipment which may be stored on the apparatus floor or other textile/plastic materials within the station.
  • Exhaust Source Capture is considered the most reliable means to significantly reduce or eliminate exposure.

Under the recommendations stated, “Given the high incidence of cancer among the fire fighters, each department should take immediate steps to reduce the levels of diesel emissions within their fire stations as urged by the IAFF. A “proven” source capture system remains the only viable option for effectively dealing with diesel exhaust emissions.”

International Association of Fire Fighters, Richard M. Duffy, Director Occupational Health and Safety Department, letter dated October 19, 1992, states:

  • General ventilation should only be used as an interim system, since general ventilation only dilutes the ambient air and does not eliminate exposure.
  • Use “local exhaust system such as tail pipe exhaust system.”

The Commonwealth of Massachusetts, Department of Labor and Industries, division of Occupational Hygiene, letter April 1, 1992, inspection of Andover Fire Department, states “Like other Carcinogens, there is no safe level of exposure to diesel emissions. Even minimal exposures are believed to involve some increased risk of developing cancer, however small that increase in risk may be.” They also report:

  • “For this reason, many fire departments have moved to install “state of the art” local exhaust ventilation systems which capture exhaust at the tailpipe.

The Commonwealth of Massachusetts, Department of Labor and Industries, Division of OccupationalHygiene, General Recommendations For Fire Stations, list guidelines to establish and maintain a low-risk environment in all fire station. Among these are:

  • Flexible hoses attached to the vehicles’ exhaust pipes and venting directly to the outside are the most effective method of removing exhaust and minimizing accumulation in the fire station. The hoses are equipped with automatic drive-away disconnect. This system does not require heated air to be removed from the building as wall fans do.
  • A less effective alternate is general ventilation. Sufficient air must be exhausted to ensure a negative pressure in the apparatus area relative to occupied areas.

Click here for more information on the hazards of vehicle exhaust.


1. Tailpipe Filters

This method involves retrofitting a device in the apparatus exhaust system to remove the diesel particulate hazard. No agency or report recommends using this method. This is because the gases, which account for 75% of the PAH in diesel fume, are not captured and pass through the device. NFPA 1500 Handbook, Paragraph 7-1.5 states…”that the carcinogenic effect of diesel exhaust is present even when the particulates (soot) are filtered out of the exhaust.”

The New York City Report found that Ceramic Filters installed in the diesel exhaust air stream did not remove the gaseous emissions.

Source Capture As The Recommended Method To Control Diesel Exhaust Emissions At The Fire Station, Jeffery O. Stull, International Personnel Protection, Inc. states “After market diesel exhaust filters add to the apparatus exhaust system may appear to clean exhaust by removing visible particulates, but still allow hazardous gases to pass through and remain within the fire station.”

The fire fighter still must breathe the carcinogenic gases of the diesel fume. The carcinogenic gases of diesel fume can remain for 18 days.


2. Air Cleaners

This method involves placing self-contained air cleaners at ceiling level in the apparatus area. As the diesel fumes rises it is treated by a series of filters and re-circulated. No agency or report recommends this method. This is because the apparatus area will begin to fill with the diesel fumes before it rises to the inlet of the air cleaner and the fire fighter still must breathe the carcinogenic diesel fumes. The carbon monoxide, nitrogen dioxide and other gases are not removed. Air cleaners cannot prevent the soot from collecting on the walls, clothing and equipment in the station.

Activated Carbon’s Effectiveness on Diesel Exhaust Gases, letter dated February 16, 1995 by Jay Kasmark, President of D-MARK, Inc. “Activated Carbon will remove the odors from Diesel Exhaust. It will not effectively remove Carbon Monoxide, Carbon Dioxide or Nitrogen Dioxide. Obviously, if Carbon does not absorb these gases they will build up within the station and will only be removed by air leakage. This is a dangerous and potential deadly situation. My recommendation is that during engine operation, hoses be adapted to the exhaust pipes and fumes be exhausted directly outside.


3. Positive Pressure

This method involves using fans to force outside air through rigid or flexible ductwork in to the apparatus area. No agency or report recommends this method. This is because the carcinogenic diesel fume is “pushed” into the office and living quarters and exposing additional people to the harmful fume. The only part of the building to have positive pressure is the living quarters and office area.

The New York City Report says to positive pressure the living quarters and office area, not the apparatus area.

The Commonwealth of Massachusetts, Department of Labor and Industries, Division of Occupational Hygiene, General Recommendations For Fire Stations says that sufficient air must be exhausted to ensure a negative pressure in the apparatus area relative to occupied areas.


4. Exhaust Fans

This method uses fans to exhaust the air in the apparatus area to the outside. Fan size, number of fans and the placement of fans will determine how effective the diesel fume can be evacuated. No agency or report supports this method. This is because the air volume to evacuate the diesel fume is excessive. From the New York City Report you find that 12 air changes per hour (the total volume of air in the station exhausted every five minutes) was found to be ineffective.

From The Commonwealth of Massachusetts, Department of Labor and Industries, Division of Occupational Hygiene, General Recommendations For Fire Stations, you find it is noted that general ventilation is less effective.

With high volume exhaust fans removing the heat from the building during the winter, additional heating equipment may have to be added.


5. Source Capture – the only logical solution to limit exposure to diesel emissions!

This method involves attaching a hose with a positive sealing nozzle to the tailpipe. The hose is connected to ductwork and an exhaust blower to discharge the diesel fume of the building. When the apparatus engine is started, the exhaust blower is activated to remove the fume. As the apparatus exits the door the hose nozzle automatically disconnects from the tailpipe. The exhaust blower is automatically turned off after the apparatus leaves the station. Several agencies and reports support this method. Only a source capture emergency vehicle exhaust system meets the requirement of limiting exposure to carcinogenic diesel fumes. The source capture system eliminates the fume before it fills the station with diesel smoke.


Why should you invest in a source capture vehicle exhaust removal system?

  1. Protect employees’ health from the toxic emissions.
  2. Protect medical supplies, medical equipment and sensitive equipment such as computer systems from carbon black and chemicals that damage electrical components.
  3. Increase employee productivity by improving morale.
  4. Reduce maintenance costs and improve the image of your facility by controlling oil-film, carbon black and odors from spreading through the work area.
  5. Reduce insurance costs by controlling the risk of workers’ compensation claims.
  6. Save money by not having to exhaust large volumes of heated or conditioned air from your workshops or bays.
  7. Prolong the interior décor of your facility (save money).
  8. Meet or exceed state, county, or city heath codes or standards.