What Is Fire-Resistant Wire for Multiple Floors?

Electric Current Requires a Closed Path

• Electric circuits do work by means of electric current flow. For electric current to flow, there must be a voltage differential across the circuit, and there must be an electrically conductive path from the area of higher voltage to the area having lower voltage. Electric wires and electric cables provide this path and supply electric and electronic devices with power. If the path is interrupted -- such as by a break in the wire -- current will stop flowing and the circuit will be turned off.

Fire-Resistant Wire Allows a Circuit to Stay On

• In the event of a fire, some circuits -- such as a fire alarm or a sprinkler control system -- may need to stay on. A circuit that has flammable insulation materials runs the risk of short-circuiting, since the insulation materials might be consumed and bare wires might contact each other. Electric wire that is “fire rated” or “fire-resistant” can withstand temperatures that can damage or destroy building structures, as well as withstand the impact loads of firefighting efforts (such as having a water jet sprayed upon the heated wire).

Fire-Resistant versus Flame-Retardant

• A fire-resistant electric wire is designed to withstand the temperatures that a structure fire may produce and still provide a circuit with power. Flame-retardant electric wire may be used in electric circuits; however, it is not designed for circuit integrity under the stresses that a structure fire may present. Flame-retardant electric wire may prevent the spread of fire into a new area; however, flame-retardant electric wire should not be used in circuits that are necessary for fire protection.

Plenum-Grade Cables

• Data and telephone cabling may be installed between floors or in a ceiling space. If the ceiling space is to be used as an air return, local electrical codes may call for “plenum-grade” cables. If a fire breaks out in a building, the data cable may be exposed to flames or temperatures that can break down some types of electrical insulation. Plenum-grade cables fall under the “flame-retardant” category rather than the “fire-resistant” category; this is because plenum-grade cables are designed to limit the amount of smoke and harmful fumes that these cables give off when they are exposed to high temperatures or flames.