Fire is a lethal force that can easily escape control. In structures, it often starts in the building's furnishings and then ignites the structure itself. One of the keys to fire control, therefore, is to prevent the fire from spreading throughout a building via its contents, usually by depriving the fire of the fuel it needs to grow. It is this premise of flame suppression that underlies most research into flame retardants.
There are several fire types and "hazard situations": nonflaming/smoldering fires, early or small flaming fires, and fully developed large-scale (called post-flashover) fires (The British Plastics Federation, 1990, p. 207). Nonflaming/smoldering fires can start from overheating of vulnerable substances or can be self-sustaining over a long period of time, after which the fire may finally break out into flame. The hazard of toxic gases gradually filling the atmosphere can lead to the incapacitation of anyone in the affected area. The goal of fire retardant developers, therefore, is to ensure that the production of toxic gas is not a dominant result of a materials decomposition.
Fire retardants play a significant role in early or small flaming fires by reducing the chance of flaming ignition and by slowing the rate of fire growth. As with smoldering fires, however, the production of toxic gases is a problem. Considered most effective on the early stages of fire growth, it is unclear the extent to which fire retardant materials affect (if at all) fully developed fires.
There is a wide range of chemical formulations and vehicle/additive combinations in use as fire retardants or as materials considered fire resistant. Polyurethanes; polyesters; epoxies and silicones; phenolics and other thermosets; polypropylene and polyethylene; polystyrene; polyamides and acrylics; polycarbonates, polyvinyl chloride, and other thermoplastics; natural polymers; halogen and phosphorus compounds; and various other ma...