Health and safety risks of firefighting

What fire risks are firefighters exposed to? For ease of discussion, the main firefighting risks are classified into four groups: those related to heat, smoke, the physical characteristics of the fireground, and finally, the psychosocial load of the activity. Some of these risks, e.g., most of the risks from heat exposure are peculiar to firefighting, while others (like psychosocial risks) also occur in other types of task.

Heat risks

Two main types of risk are associated with the heat from a blaze. One is that the heat generated by a fire in a confined or semi-enclosed space can produce hostile fire events (sometimes called "thermal phenomena") that are particularly hazardous to firefighters. But also, even without hostile fire events, working in a high temperature environment poses a big risk to firefighters’ health and safety from the specific and potentially severe disorders it entails.

Hostile fire events

Two hostile fire events ("thermal phenomena") are particularly dangerous for firefighters. The first is known as backdraft. This is a smoke explosion. Among its other properties, smoke is flammable and explosive. Backdraft occurs when air is suddenly re-introduced into an overheated, oxygen-starved environment. This happens, for example, where the fire is confined to a room which is well-insulated or sealed-off from the outside, so there is little or no combustion agent (e.g., the oxygen content of the air). As a result, combustion is incomplete: the fire smoulders, no longer produces flames and contains a lot of soot particles. Even so, significant amounts of uncombusted gases are given off, producing excess pressure inside the room. As the temperature rises, the gases expand and this excess pressure increases. In these conditions, sufficient combustion agent can be introduced by ventilating the room, e.g., opening a door to cause a very rapid oxygen enrichment of the combustible hot smoke and uncombusted gases, producing an explosive effect. Opening a door or breaking a window can feed oxygen to the fire area and thus cause an explosion.

While characterized by an explosion, backdraft is also accompanied by a shock and heat wave. Exposed individuals are likely to suffer a range of organ damage known as "blast". Primary blast consists of internal injuries caused by the direct action of the shock wave in the body (e.g., pneumothorax, acute lung injury [or adult respiratory distress syndrome], ruptured eardrum, subarachnoid haemorrhage, myocardial infarction, peritonitis, etc.). Secondary blast comprises injuries resulting from the high-speed projection of explosion debris. Casualties may suffer superficial or deep multiple lesions. Tertiary blast injuries are caused by the victim being projected within the fire room (e.g., fall, impact). Finally, quaternary blast comprises burn injuries, smoke inhalation injuries and injuries from being buried under collapsing debris. The severity of the injury depends on the intensity of the explosion, the conditions of propagation of the shock wave (e.g., a compartment explosion is accompanied by haze heat and reverberations) as well as individual factors (e.g., the position and weight of the exposed person). Needless to say that exposure to a backdraft can be fatal.

The second hostile fire event, which is no less dangerous, is that of flashover a near simultaneous ignition of all flammable gases which have built up across the ceiling of an adequately ventilated compartment. This can happen when a fire develops in a semi-open space. Initially, the fire has sufficient air supply to grow. It produces smoke. The smoke, heated by the point of origin of the fire, produces a rise in temperature resulting in pyrolysis of all the combustible materials in the room (e.g., partition walls, furniture, decorations, etc.). The unburned gases distilled by the combustible materials in the environment will mix with the smoke and create a "gas layer" in the upper part of the room. At this point, the seat of the fire situated in the lower part of the room is still being supplied with oxygen and so the temperature continues to rise. It is then enough for the "gas layer" to reach its ignition temperature (e.g., autoignition temperature) or come into contact with burning materials transferred by the point of origin for the fire to spread across to all the distilled smoke and gases present in the fire room. This is flashover.

Exposure to a flashover is invariably fatal because it causes a surge in temperature to above 1,000 degrees Celsius.

Given the severity of these phenomena which can develop during any fire in an enclosed or semi-open space, any firefighting operation must necessarily be preceded by a risk assessment done from outside by the incident commander. He must first determine whether the indicators of these fire events are there (e.g., is the window glass blackened or opaque? Is the smoke being pushed out by existing ventilation or the roof? Are the flames visible? etc.) and whether steps need to be taken to make the fireground safe (e.g., establishing a safety perimeter). Based on the risk assessment, the incident commander will determine the most appropriate fire attack technique (e.g., offensive vs. defensive). If rescue or reconnaissance personnel need to be committed, the incident commander will take different prevention and protection measures to ensure their safety. These will include at least ensuring that they wear full personal protective equipment, that there is an escape route if the way in/out has become unsafe, a "two-out" standby team is ready to go in at the slightest sign of danger, and that a sufficient number of charged water appliances are on hand.

It is vital for the tactical actions carried out by the different crew members to be coordinated by the incident commander and for there to be efficient communication between the "two-in" attack team and the outside. In conditions that can produce fire events, a lack of communication and coordination can have tragic consequences. For example, if a firefighter working outside a burning structure freelances independently of both incident command and the deployed entry team by venting the structure (e.g., by opening a door, breaking a window or by positive pressure ventilation), his action may in some circumstances improve matters, but can also make things worse by causing a backdraft or flashover that will put his entry team colleagues' lives in danger.

Face with these incipient fire events, it is vital that attack firefighters should be able to respond appropriately, quickly and calmly. That means that they must be able to fully read a fire, including understanding the specific indicators.