Hazards in different firefighting tasks

The following list of various tasks gives a picture of the wide variety of environments where firefighters must face different kind of hazards.

Firefighting

Heat and fire in different forms are the most important hazards in firefighting. The thermal hazards in ground fire conditions are usually radiant or convective energy from open flames, explosions, flashing or back-draughts or radiant heat from hot surfaces, objects, etc., falling objects, debris and hot materials or objects exposed to contact heat (Coletta et al., 1976). Hoschke (1981) divides the thermal conditions into three categories, i.e., routine, hazardous and emergency, each defined by a range of air temperature and a range of radiant flux (Fig. 22.1). Figure 22.1 also shows why high thermal protection is needed, e.g., exposure to a radiant heat level of 4kW/m2, which is quite normal in structural firefighting (Rossi, 2003), causes second-degree burns to bare skin in 30 seconds.

The minimum required function of protective equipment in hazardous conditions, e.g., during entry into a burning room, is to protect the user sufficiently throughout the operation time and to minimize heat stress. In emergency conditions the protective equipment should not hinder escape (Makinen, 1991). It has been estimated that it takes 3-10 s to escape from aircraft or vehicle crash fuel spills with heat flux intensities peaking between 167 and 226kW/m2 (Holmes, 2000a).

The heat flow can today be higher than shown in the Hoschke-Table (Hoschke, 1981) because of increased fuel loads from the use of synthetic building materials, interior finishes and furnishings. Lawson (1997) showed that very high heat fluxes, as high as 30 kW/m2, with a temperature of 175 0C on the ground are possible. Rossi (2003) measured radiant heat fluxes typically between 5 and 10 kW/m , and the temperature reached 100-190 0C at 1 m above ground level.

The introduction of properly maintained and functioning smoke detectors, residential alarm systems, and modern fire service communications systems have made it possible for firefighters to arrive on the fire scene before a structure is fully involved, and they can start extinguishing at the source of the fire. The increased performance level of personal protective equipment provides a

22.7 The thermal environment of firefighters in firefighting (Reprinted from Fire Safety Journal, Vol. 4, Hoschke 'Standards and specifications for firefighter's clothing', pp. 1 25-137 1981, with permission from Elsevier).

sufficient delay in heat transfer for the firefighters to operate longer, and to enter a very hazardous zone where the temperature is high enough to increase the possibility of the structure collapsing. If there is no early warning device in the protective equipment or clothing, the operating time is limited by the air supply of the breathing apparatus, which normally contains an air supply for 20-30 minutes. Thus escape may not be possible in time. In addition to thermal hazards, firefighters face electrical hazards, climatic conditions, water, mechanical hazards, poor visibility, biological and chemical hazards, and physiological/heat stress.

Wildland firefighting

Wildland firefighters generally operate for long periods (8-16h/day) and are generally exposed to a radiant heat flux of 1 kW/m2 to 8 kW/m2. But they can be exposed during increased activities in extreme fire conditions for shorter periods to higher radiant heat fluxes up to 100kW/m2. The hazards in wildland fires vary, depending mainly on the following factors (Donarski and Poulin, 2004): fine fuel load, fire danger index, slope, drought factor, air temperature, relative humidity, wind velocity, fuel volume. Heavy working at high temperatures for long periods exposes the firefighters to heat stress. These problems are dealt with in a special issue of International Journal of Wildland Fire (Weber, 1997).

Chemical attacks and hazardous environments

The increased use and transportation of toxic chemicals raises the risk of accidents. In such situations the first responders often do not know what chemical(s) are involved, or which hazard level they will encounter. In certain countries, including the UK, 'Hazchem' coded plates are fitted to road tankers. The number and letter codes give rescue teams information on the nature of the contents, the level of hazard, and advice on the safest ways of treating any spills.

Motor vehicle accidents

When removing victims from the accident vehicles many tools with a high level of working power are needed. This creates mechanical hazards as well as flying pieces of sharp broken glass, sharp metal, etc. There is also the risk of the fuel tank exploding. The normal traffic presents an additional risk on the roads and highways.

Other types of rescue work

In urban search and rescue tasks, firefighters face a wide range of hazards, such as: (Stull et al., 1996a)

• physical hazards (metal and masonry debris, working around heavy equipment, floating and submerged debris, slips and falls)

• thermal hazards (exposure to cold water, air and radiant temperatures causing heat stress, subzero temperatures)

• flame and heat related hazards

• chemical hazards (broken gas lines, open solvent containers)

• biological hazards (direct exposure to bacteria-contaminated water, involvement in emergency medical services, contact with victims having infectious diseases).

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