This resource does not replace the Occupational Health and Safety Act (OHSA) and its regulations and should not be used as or considered legal advice. Health and safety inspectors apply and enforce these laws based on the facts they find in the workplace.


Today’s fires have the potential to give off a myriad of fire gases such as hydrogen cyanide (HCN), carbon monoxide, acrolein, formaldehyde and glutaraldehyde.


Firefighters may be exposed to levels of gases which result in health effects and exceed occupational exposure limits.

HCN is a deadly gas that occurs as a by-product of combustion. Symptoms of HCN exposure could range from a headache or blurred vision to seizures or death. Long-term health effects could include respiratory problems, heart disease or brain damage.

Prolonged exposure to carbon monoxide can lead to brain damage. Acrolein is a suspected human carcinogen and formaldehyde is a known carcinogen. Repeated exposure to glutaraldehyde can cause asthma.

Actions for employers

Employers should:

  • develop a program to reduce firefighter exposure to fire gases, in consultation with the joint health and safety committee or health and safety representative
  • coordinate with local health authorities to ensure there are treatment protocols and/or antidotes for fire gas exposures

Reducing exposure to fire gases

Consider the following elements in your program to reduce firefighter exposure:

  • awareness training on topics such as the properties of fire gases, recognizing potential exposure hazards, and signs and symptoms of exposure
  • air monitoring (including at the rehab area) to detect fire gas levels
  • protocols for respiratory protection, on-scene decontamination of equipment and personnel, personal protective equipment, transportation of contaminated equipment and post-event decontamination
  • reporting and documentation of air sampling and exposure
  • operating policies or guidelines

Hydrogen cyanide exposure

The greatest amounts of HCN are released during the smoldering stages of fire. HCN is immediately dangerous to life or health at 50 parts per million.

Elevated levels of HCN can be produced from fires such as a pot on a stove or other cooking fires, car fires or dumpster fires. An average small kitchen fire may produce 75 parts per million of HCN. Firefighters may also be exposed to elevated levels of HCN during overhaul operations and fire investigations.

The antidote for HCN is cyanocobalamin.

Applicable regulations and acts



Read firefighter guidances notes: