Fire alarm cable types explained
The different cable types used in fire alarm installations, what the standards require for each circuit type, and why cable selection matters for system survival during a fire.
Cable choice is one of the most technically important decisions in fire alarm installation — and one of the most frequently misunderstood. The wrong cable on the wrong circuit can mean the system stops functioning during the fire itself, precisely when it is most needed. BS 5839-1 sets out specific requirements for cable performance on different parts of the system, and these requirements have real consequences for the type of cable that must be used.
Cable Survival During Fire
Fire alarm cables serve two functions: they carry signal and power under normal conditions, and they must continue to do so under fire conditions long enough to ensure the alarm remains active during evacuation. A cable that fails early in a fire — before all occupants have evacuated — has failed in its primary purpose.
BS 5839-1 defines two levels of cable performance for fire alarm circuits based on the consequences of circuit failure:
- Standard cables — for circuits where failure during a fire is acceptable because the circuit is not critical to the alarm function
- Enhanced fire survival cables — for circuits where continued operation during a fire is essential, including alarm circuits and certain power circuits
Cable types in detail
The Main Cable Types Used in Fire Alarm Systems
| Cable type | Description | Typical application |
|---|---|---|
| Standard fire alarm cable (FP200 or equivalent) | Enhanced fire survival cable with mineral insulation or fire-resistant insulation and sheath. Maintains circuit integrity at temperatures up to 850°C for a defined period | Detection circuits, sounder circuits, and all circuits where continued operation during a fire is required under BS 5839-1 |
| Standard PVC cable | Conventional PVC-insulated cable with no enhanced fire survival properties. Fails relatively quickly when exposed to fire | Not appropriate for detection or sounder circuits. May be used for mains supply to the panel where protected by a conduit or in a separate service route — with limitations |
| Screened fire alarm cable | Fire survival cable with an additional metallic screen (foil or braid) to reduce electromagnetic interference | Addressable loop circuits where the digital communication signal requires shielding from interference sources |
| Mineral insulated cable (MICC) | Copper conductors insulated with compressed magnesium oxide and sheathed in copper. Survives extreme temperatures and mechanical damage | High-risk environments where maximum cable survival is required — plant rooms, high-temperature areas, and some industrial applications |
Which circuits need enhanced survival cable
BS 5839-1 Cable Requirements by Circuit Type
The standard distinguishes between circuits based on whether their failure during a fire would affect the functioning of the system. The key principle is: if the circuit is needed to raise or sustain the alarm during a fire, it needs enhanced fire survival cable.
| Circuit type | Enhanced survival cable required? | Reasoning |
|---|---|---|
| Detection circuits (detector loop or zone circuit) | Yes | Circuit failure removes detection capability — the system may fail to detect a developing fire if the cable fails early |
| Sounder circuits | Yes | Sounder circuit failure during a fire silences the alarm — occupants in areas served by those sounders receive no warning |
| Mains supply to panel (from distribution board) | Recommended — or routed away from fire risk areas | Mains failure causes the system to run on battery — acceptable for a period but reduces reserve capacity during a prolonged incident |
| Ancillary output circuits (door releases, lift recall) | Yes, where the output function is needed during the fire | A door release that fails to operate because its cable has burned through may trap occupants; a lift that does not recall may be used by evacuees |
| Fault monitoring circuits (remote fault signalling) | Not usually | Fault signalling is not a life safety function during the fire itself |
Cable installation and protection
How Fire Alarm Cable Must Be Installed
Even the correct cable type provides limited protection if it is installed incorrectly. BS 5839-1 requires that fire alarm cables are:
- Segregated from other services — fire alarm cables should not be run alongside mains power cables or data cables, which can introduce interference and are not subject to fire survival requirements
- Identified at both ends and at junction boxes — all cables must be clearly labelled to enable maintenance and fault-finding
- Protected against mechanical damage where they run in areas susceptible to physical damage — conduit, trunking, or armoured cable may be appropriate
- Routed away from areas of high fire risk where possible — a cable running through the room most likely to be the seat of the fire is more vulnerable than one routed via a protected service duct
Common questions
Frequently Asked Questions
No — red is a common colour for fire alarm cable but it is not a technical requirement of BS 5839-1 for all circuits. The standard requires cables to be identified and labelled, not necessarily coloured red. Red is conventional and helps installers, maintenance engineers, and building services contractors quickly identify fire alarm wiring — which is one reason it remains widespread. The detailed requirements on cable colour are covered in our separate guide to red fire alarm cable.
In limited circumstances — for example, mains supply wiring to the panel where the cable is routed in a protected service duct away from fire risk areas, or for low-voltage circuits that are not part of the alarm or detection function. In practice, most competent installers use enhanced fire survival cable throughout the installation to simplify compliance and reduce the risk of argument about whether a particular run needs enhanced performance or not.
The cable type should be documented in the original installation records, which the contractor should have provided on completion. If those records are not available, a competent fire alarm engineer can identify the cable type by inspection — the cable will typically be printed with its specification including the standard it meets. If the installation records are missing, a full survey is advisable to confirm that the installed cable meets current requirements throughout.