Jean-Marie Maldijan, Schneider Electric, explained the importance of fire resistance in electrical components, such as switches, plugs and circuit breakers.
Electrical connections can deteriorate because of wear of contacts, loosening of wire screws, incorrect installation or damage or simply by corrosion of contacts, resulting in resistance which can cause very high local temperatures when current flows.
Such electrical parts are often situated very close to larger flammable items (such as casings or internal parts in consumer white goods) so a small fire in the polymer in e.g. a switch can spread rapidly.
These parts can be made of either thermoplastics or thermosets. Fire testing is by either UL94 or the GWFI (Glow Wire Flammability Index). GWFI pass can be achieved by polymers which melt away from the applied glow wire. Intumescent PIN flame retardants can ensure fire safety and pass both tests, and PIN systems generating ceramic-based char layers are preferable because carbon-based or graphite char is generally not electrically insulating.