Knowledge and understanding
Understand all associated hazard knowledge
Cables are predominately found in buildings or modes of transport, and may present hazards including:
- Hazardous products of combustion
Cabling may become unsecured or exposed for reasons including:
- Heat, potentially due to fire or explosion
- Partial or structural collapse of a building
- Damage to a mode of transport in a collision or fire
- When accessing a casualty in a structure or mode of transport
Cabling, including electrical, communication and data cables, sometimes relies on surface mounted conduit and trunking. Cabling may be concealed above suspended ceilings, with little or no fixing.
Most cables are sheathed or protected with polyvinyl chloride (PVC), polyethylene (PE) or thermoplastic polyurethane (TPU). In a fire, these plastics release dioxins, hydrogen cyanide and hydrogen chloride. For further information refer to Fires and firefighting – Smoke and fire gases.
From 1 January 2016, regulations require that all new wiring systems use metal, rather than plastic, to support cables in escape routes, to prevent their premature collapse in a fire. However, electrical installations fitted before changes to the regulations, or that do not conform to the regulations, may still present a hazard.
Lightweight cable fixings may be present in older buildings due to electrical upgrades and retrofitted electrical sockets, light fittings, security or fire alarms and data cables.
Plastic conduit or trunking that is surface mounted on ceilings and walls will fail at relatively low temperatures of around 100oC. Aluminium trunking may fail due to heat. Suspended ceilings may distort or fail at relatively low temperatures.
If a suspended ceiling, conduit or trunking fails, cables may be released, potentially at some distance from the seat of a fire in a building. As a result, cables may present a risk of entanglement or electrocution to personnel.
Modes of transport
If the interior of a mode of transport is damaged through collision or fire, cables may present an electrocution or entanglement hazard. Cables run through the chassis, usually behind interior furnishings; there is a risk of cutting through cables when carrying out a rescue.
Older aircraft have cables under tension; these usually run from the flight deck to moving surface components, such as the rudder, elevators and flaps. If these components are operated by the aircrew, or moved from outside the aircraft, these internal cables will move and could result in entanglement.