Toxicity and radiated heat hazards of smoke

Smoke produced by combustion or pyrolysis is composed of solid particles, gases and aerosols. Their chemical composition depends on the materials involved in the combustion, the state of combustion (e.g., complete vs. incomplete) and the oxygen concentration.

Smoke released from house fires can contain 200 or more toxic gases. The most common are carbon monoxide (CO), carbon dioxide (CO2), hydrogen chloride (HCl), hydrogen cyanide (HCN), nitrogen oxides (NOx) and soot particles. Not uncommonly, it may also contain benzene, toluene, sulphur dioxide (SO2), aldehydes, acrolein, trichloroethylene, and others. The effects of contact with or inhalation of these gases and particles obviously depend on their concentration in the air and the exposure time.

The effects of exposure to some chemicals may not appear until much later on because diseases like cancer have long development periods. Medical surveillance throughout but also after the end of working life is vital for firefighters.

The smoke that firefighters are exposed to if not wearing a self-contained breathing apparatus (SCBA) contains different toxins and irritants, typically resulting in multiple poisoning. A self-contained breathing apparatus can prevent these toxins being inhaled. Wearing them should be compulsory where there is visible smoke, but also during fire scene overhaul, because residual embers give off large quantities of what may be invisible and odourless carbon monoxide and other toxic gases.

The temperature of smoke adds to its toxicity. Hot smoke gives off radiant heat which at certain temperatures can ignite combustible materials. They can cause serious injury to human beings. Entering the airways at a temperature below that which causes fatal burns, hot smoke destroys the lungs’ innate defence system, heightens the action of the toxins it contains and passes into the bloodstream.

Smoke opacity

Fire smoke can be more or less opaque depending on the concentration of solid particles and aerosols. Dense, thick smoke forms a screen that reduces visibility sometimes to zero and especially deadens sound waves. Sounds and voices are muffled. That makes it hard to judge distances. In smoke, all visual and sound bearings are lost (or missing). Firefighters are effectively having to find their way around rooms they are normally unfamiliar with as if they were partially sighted or blind, hearing impaired or deaf. Moving forward through or reconnoitring the scene in such circumstances carries clear high risks: firefighters may lose their sense of direction and head back to the seat of the fire when they think they are exiting. This is the mistake that may cost lives if the self-contained breathing apparatus (SCBA) cylinder’s reserves are too low to turn back or if a fire event is developing. They may also sustain injury tripping over objects or losing their teammate who is close by because they can no longer locate or hear his calls. Smoke puts firefighter safety particularly at risk and renders on-scene rescue personnel operations very difficult.

Text 9.

Physical hazards

 

Fire control exposes firefighters to a wide range of physical and structural hazards, largely determined by the characteristics of the fireground. First, moving forward through a compartment whose boundaries, size and height differences are hidden by opaque smoke can result in falls, slips and collisions with objects. Also, a structure fire (e.g., house, shed, etc.) increases the risk of collapse because combustion or prolonged exposure to heat alters and reduces the structural strength of materials. Given the potential severity of collapse injuries to fireground personnel, the risk assessment prior to any operation must marshal all available knowledge about the yield points of the structural materials used and their loss-ofstrength behaviour in fire. Finally, firefighting operations involve risks from energy sources in the structure – electricity, gas, etc. which do not mix with water or fire and involve potentially fatal risks of electrocution and explosion. Before committing entry teams, the risk assessment must identify the energy sources present in order to cut off the supply. A word must be said here about new risks emerging in firefighting. The solar panels equipping increasing numbers of house roofs in recent years are a source of growing concern to fire and rescue service personnel because they remain powered even when the mains power is off, leaving the risk of electrocution.

Emergency travel to fire stations or call-outs to incident sites is also responsible for many accidents. The emergency services’ road traffic accident record is a source of growing concern. It could be brought down by improvements to vehicle markings. Specific emergency vehicle driver training modules for difficult or dangerous conditions would also be a good idea.

Text 10.

Psychosocial risks

The risks considered above and the macho culture prevalent in many fire services of suppressing emotions and feelings often mean that scant attention is paid to the psychosocial risks of firefighting missions.