Skip to main content

Developed and maintained
by the NFCC


Smoke and fire gases

Hazard Knowledge

Smoke is generally a mixture of fine solid particles, droplets of water and other liquids, and gases given off by the materials involved in the fire. The most important toxic product in any fire is carbon monoxide, which is produced by all organic materials when they burn. However, tests have shown that a 'cocktail' of nearly a hundred gases can be detected by specialised equipment. In addition to producing smoke, fire can reduce oxygen levels, either by consuming the oxygen or by displacing it with other gases. Heat is also a respiratory hazard, as superheated gases burn the respiratory tract.

Smoke is made of:

  • Particles: unburned, partially burned, and completely burned substances
  • Vapours: fog-like droplets of liquid that can poison if inhaled or absorbed through the skin, such as benzene, formaldehyde and other volatile organic compounds
  • Toxic gases: carbon monoxide (CO) can be deadly, even in small quantities. Hydrogen cyanide results from burning plastics and interferes with cellular respiration

Regulation 7(5) of the Control of Substances Hazardous to Health Regulations (COSHH) sets out clear requirements for the control of carcinogenic and mutagenic substances, including a requirement that exposure be reduced to as low as is reasonably practicable.

Working in smoke and darkness reduces visibility and the effectiveness of other sensory perceptions, making navigation difficult even in relatively simple environments. When committed to a building there is a strong possibility that firefighters will encounter conditions limiting visibility and affecting their key human senses. For example, when deployed to locate a fire internally in a structure, firefighters wearing breathing apparatus (BA) will often rely on touch and hearing as their primary senses; their sense of smell will be lost and their visual sense impaired when working in smoke and darkness.

Smoke, steam and fire gases can increase the distance electricity can jump and may result in arcing between sources, affecting firefighter safety.

See National Operational Guidance: Utilities and fuel