What type of low voltage wiring is used for fire alarms?

The type of low voltage wiring used for fire alarms is FPL, which stands for Fire Power Limited cable. This designation indicates that the cable is specifically designed for fire alarm applications, adhering to the National Fire Protection Association (NFPA) standards, including the National Electrical Code (NEC). FPL cable is constructed to be resistant to a variety of environmental factors, including moisture and temperature variations, and is designed to limit the power supply in order to reduce the risk of fire hazards.

The other options, while commonly used in various wiring applications, do not meet the specific requirements for fire alarm systems. CAT5e is primarily used for networking applications, THHN is a type of thermoplastic insulated wire typically used in general wiring for buildings, and NM-B is non-metallic sheathed cable used primarily for residential wiring. None of these carry the necessary fire resistance or reduced power characteristics that FPL wiring offers, making FPL the correct choice for fire alarm wiring.