Fire Alarm Cable: Types, Sizes, Standards & Selection Guide

Fire alarm cable is designed to connect fire detection and alarm devices while providing the electrical performance and, where required, fire resistance needed for the system to continue operating during a fire. The correct cable depends on the circuit type, required fire performance, conductor size, installation conditions, cable length and applicable standards.

Choosing the right fire alarm cable is important because cable selection affects circuit reliability, voltage drop, installation safety and system performance. This guide explains the main types, common sizes, UK standards and practical factors to consider when selecting fire alarm cable.

Key Takeaways

• Fire alarm cable is designed specifically for fire detection and alarm system wiring.
• Common configurations include 2 core cables, with conductor sizes such as 1.0 mm², 1.5 mm² and 2.5 mm² available for different applications.
• Fire resistant, enhanced fire resistant, screened and LSZH cables offer different characteristics and should not be treated as interchangeable.
• Cable size should be selected based on the circuit, load, cable length, voltage drop, installation conditions and system requirements.
• BS 5839-1 and BS 7629-1 are important UK standards to consider, depending on the application.
• “Type 2 alarm cable” is not simply another name for a 2 core fire alarm cable.
• There is no single “best” fire alarm cable for every installation.

What Is a Fire Alarm Cable?

A fire alarm cable is a cable specifically designed for use in fire detection and fire alarm systems. It carries power and/or signals between equipment such as fire alarm control panels, detectors, sounders, manual call points and other connected devices.

Depending on the system and installation requirements, fire alarm cable may need to provide a defined level of fire resistance so that important circuits can continue to operate for a specified period during a fire.

The cable construction can vary depending on the application. Some cables have enhanced fire resistance while others may include screening or low smoke zero halogen (LSZH) materials where the installation requires them.

Unlike ordinary electrical cable, fire alarm cable must be selected with the requirements of the fire alarm system and applicable standards in mind.

What Cable Is Used for Fire Alarms?

The cable used for a fire alarm system depends on the type of circuit, the required fire performance and the installation environment.

In UK installations, fire resistant cables designed for fire detection and alarm applications are commonly used where circuit integrity during a fire is required. Suitable cable types can include screened, fire resistant multicore cables manufactured for applications covered by relevant standards.

A common configuration is a 2 core fire alarm cable, but the number of cores and conductor size should be selected according to the actual circuit requirements rather than assuming one configuration is suitable for every system. Cable selection should also consider the total cable run and voltage drop.

Types of Fire Alarm Cable

Fire alarm cables are available in different constructions and performance categories. The correct type depends on the requirements of the fire alarm system and the installation environment.

Standard Fire Resistant Cable

Standard fire resistant cable is designed to maintain circuit integrity for a specified period when exposed to fire, depending on its construction and certification.

These cables are commonly used where the fire alarm circuit needs to continue operating during a fire. The required performance should be confirmed against the system design and applicable standards.

Enhanced Fire Resistant Cable

Enhanced fire resistant cable is designed to provide a higher level of circuit integrity under defined fire test conditions than a standard fire resistant construction. It may be selected for critical circuits or installations where a longer survival period or higher fire performance is required.

The required cable performance should always be determined by the system design and applicable fire alarm requirements rather than simply choosing the cable with the highest rating.

Screened Fire Alarm Cable

Screened fire alarm cable includes a conductive screen designed to help reduce the effects of electromagnetic interference (EMI) and electrical noise. Screening can be useful in environments where fire alarm circuits may be exposed to interference from other electrical equipment.

However a screened cable is not automatically better for every installation. The need for screening depends on the circuit design and installation environment.

LSZH Fire Alarm Cable

LSZH stands for Low Smoke Zero Halogen. LSZH cable is designed to produce very low levels of smoke and avoid halogenated gases when exposed to fire.

This can be particularly important in enclosed or occupied environments where smoke and corrosive gases could create additional hazards.

It is important to understand that LSZH describes the material characteristics of the cable. It does not, by itself, mean that the cable has a particular level of fire resistance.

Fire Alarm Cable Sizes

Fire alarm cable is available in different conductor sizes and core configurations. The appropriate size depends on the circuit requirements, current, cable length, voltage drop, installation method and required fire performance. There is no universal fire alarm cable size that should be used for every installation.

2 Core Fire Alarm Cable

A 2 core fire alarm cable is a common configuration used for fire detection and alarm circuits. The two conductors can be used to carry power and/or signals depending on the circuit design. However 2 cores only describe the number of conductors. It does not specify the cable's fire resistance, conductor size or overall performance.

For this reason a 2 core cable could have different conductor sizes and different construction characteristics depending on the manufacturer and application.

Cable Length and Voltage Drop

Cable length is another important factor when selecting a fire alarm cable. As the cable run becomes longer, conductor resistance increases, which can contribute to voltage drop along the circuit.

The voltage available at the end of the cable must remain suitable for the connected fire alarm devices. This is particularly important for circuits with long cable runs or multiple connected devices.

For a more detailed explanation of cable length, conductor resistance and voltage drop in fire alarm circuits see our fire alarm voltage drop calculation guide.

Worked Voltage Drop Calculation

Consider a simple 24 V DC fire alarm circuit with:

The resistance value is only an illustrative example. For an actual installation use the resistance stated in the manufacturer's technical data and account for the conditions required by the relevant design calculation. Because the current travels from the panel to the device and returns to the panel, the approximate circuit length is:

Circuit length = 100 m × 2 = 200 m

Convert 200 m to kilometres:

200 m = 0.2 km

Now calculate the resistance of the complete circuit:

Circuit resistance = 12.1 Ω/km × 0.2 km

Circuit resistance = 2.42 Ω

The voltage drop can then be calculated using:

Voltage Drop = Current × Resistance

Voltage Drop = 1.0 A × 2.42 Ω

Voltage Drop = 2.42 V

Therefore, the approximate voltage available at the end of the circuit would be:

End voltage = 24 V − 2.42 V

End voltage = 21.58 V

So, under these simplified assumptions, the circuit would have an approximate 2.42 V voltage drop, leaving about 21.58 V at the far end.

This calculation demonstrates why cable length, conductor resistance and circuit current all matter when selecting a fire alarm cable. For a more detailed explanation of the calculation method see our voltage drop calculation guide.

In a real installation, the calculation should use the manufacturer's actual cable resistance, the relevant operating conditions, the complete circuit configuration and the connected load. The device manufacturer's minimum operating voltage and applicable fire alarm design requirements must also be checked.

• One way cable length: 100 m
• Circuit current: 1.0 A
• Cable: 1.5 mm² copper conductor
• Example conductor resistance: 12.1 Ω/km at 20°C

1.0 mm² Fire Alarm Cable

1.0 mm² fire alarm cable is available for certain fire alarm and detection applications where the circuit requirements allow its use.

Whether 1.0 mm² is suitable depends on factors such as cable length, circuit load, installation conditions and the required voltage at the connected devices. It should therefore be selected based on calculation and system requirements rather than simply choosing the smallest available cable.

1.5 mm² Fire Alarm Cable

A 1.5 mm² fire alarm cable is a commonly available size for fire alarm installations. The larger conductor cross sectional area provides lower resistance than a smaller conductor of the same material and length. This can help reduce voltage drop on suitable circuits.

However 1.5 mm² should not be treated as a universal requirement. The correct size still depends on the specific circuit design and applicable requirements.

2.5 mm² Fire Alarm Cable

The 2.5 mm² fire alarm cable has a larger conductor cross sectional area and therefore lower conductor resistance than smaller sizes of the same conductor material.

It may be considered where circuit length, load or voltage drop calculations indicate that a larger conductor is appropriate. The cable must still meet the required fire performance and installation requirements for the specific system.

How to Choose the Right Fire Alarm Cable?

Selecting a fire alarm cable involves more than choosing a conductor size. Use the following steps to assess the requirements of the installation.

1. Identify the Circuit and Application

First determine what the cable will connect and how the circuit operates. Different fire alarm circuits can have different requirements so the cable should be selected according to the system design rather than using one cable type throughout an installation without checking.

2. Determine the Required Fire Performance

Check how long the circuit needs to maintain its function under fire conditions and what level of fire performance is required. Standard and enhanced fire resistant cables are designed for different performance requirements so the cable specification should match the system design.

3. Check Conductor Size and Configuration

Determine the required number of cores and conductor cross sectional area. Common options include 2 core cables with conductor sizes such as 1.0 mm², 1.5 mm² and 2.5 mm², but other configurations may also be available.

If you are comparing cable sizes for a particular installation our electrical cable size guide can help explain the main factors involved in cable selection.

4. Consider Cable Length and Voltage Drop

Calculate the expected voltage drop over the complete cable run. A longer cable run generally has greater resistance, which can result in greater voltage drop.

The calculation should consider the conductor resistance, circuit current, cable length and system voltage. The voltage at the end of the circuit must remain within the required operating range of the connected devices.

5. Consider the Installation Environment

Consider where the cable will be installed and whether it may be exposed to conditions such as:

These factors may affect whether a screened, LSZH, mechanically protected or otherwise specialized cable is appropriate.

• Electromagnetic interference
• Mechanical damage
• High temperatures
• Moisture
• Confined or occupied spaces
• Other electrical services

6. Verify Standards and Manufacturer Requirements

Finally, check that the selected cable meets the relevant standards, certification and manufacturer requirements for the intended application. The cable specification should be compatible with the fire alarm system design and the requirements applicable to the building.

Fire Alarm Cable Standards in the UK

UK fire alarm cable selection should take account of the relevant standards for the system and cable construction.

BS 5839-1

BS 5839-1 provides recommendations for the planning, design, installation, commissioning and maintenance of fire detection and fire alarm systems in non domestic premises. The current edition is BS 5839-1:2025, published by BSI in April 2025.

This standard is concerned with the fire alarm system as a whole, including the design and installation requirements that influence cable selection.

BS 7629-1

BS 7629-1 covers certain fire resistant, screened, fixed installation multicore cables used in applications including fire detection and fire alarm systems.

When selecting a cable, check its actual construction, certification and stated applications rather than assuming that any cable described as fire alarm cable automatically meets a particular standard.

Other Relevant Standards

Other standards may apply depending on the cable construction, fire performance and installation. For example, standards relating to fire resistance, circuit integrity, smoke emission and halogen characteristics may be relevant to a particular cable.

The exact requirements should therefore be checked against the project specification and the cable manufacturer's technical documentation.

What Is Type 2 Alarm Cable?

Type 2 alarm cable is a term associated with cable classifications used for alarm and security systems, including BS 4737 cable. It should not be confused with a 2 core fire alarm cable. 2 core simply describes the number of conductors in a cable, whereas Type 2 refers to a particular cable classification and construction.

For example, a Type 2 alarm cable may use copper conductors with PVC insulation and a PVC sheath. Its suitability depends on the intended alarm or security application and the relevant specification. Therefore, if someone searches for “Type 2 alarm cable,” they should check the actual cable standard and application rather than assuming it means a fire resistant 2 core fire alarm cable.

How Much Does Fire Alarm Cable Cost?

The price of fire alarm cable varies depending on the cable specification and quantity purchased.

Important price factors include:

For example a 2 core 1.5 mm² fire alarm cable with enhanced fire performance can cost more than a simpler cable with fewer performance requirements. Because cable prices change between suppliers over time, it is better to compare the complete specification rather than choosing a cable based only on price.

• Conductor size
• Number of cores
• Standard or enhanced fire resistance
• Screened or unscreened construction
• LSZH or other sheath materials
• Manufacturer
• Certification and testing
• Drum or reel length

Can Fire Alarm Cable Be Run With Other Cables?

Fire alarm cables should not simply be installed alongside other electrical or data cables without considering the applicable installation requirements. Other cables can create potential issues involving electromagnetic interference, segregation, mechanical protection and maintenance.

The required separation or installation method depends on the system design, cable type, building and applicable regulations or standards. Where different services share the same route, the installation should be designed and installed so that the fire alarm system remains reliable and compliant.

Fire Alarm Cable vs Regular Electrical Cable

Fire alarm cable and ordinary electrical cable can look similar, but they are designed for different applications.

A regular electrical cable should not automatically be substituted for a specified fire alarm cable simply because it has a suitable conductor size.

Conclusion

Choosing the right fire alarm cable requires more than selecting a cable by size or price. The cable must be appropriate for the fire alarm circuit, required fire performance, conductor configuration, cable length, voltage drop and installation environment.

Common options include 2 core cables in sizes such as 1.0 mm², 1.5 mm² and 2.5 mm² while standard, enhanced, screened and LSZH constructions are available for different requirements.

Always check the complete cable specification, relevant UK standards and manufacturer documentation before selecting or installing fire alarm cable. For critical fire alarm installations, cable selection should form part of the overall system design and be carried out in accordance with the applicable requirements.

FAQs

What cable is used for fire alarms?

Fire alarm systems commonly use purpose designed fire resistant cables, with the exact cable type depending on the circuit, required fire performance, installation conditions and applicable standards.

What size cable is used for fire alarms?

Commonly available sizes include 1.0 mm², 1.5 mm² and 2.5 mm², but there is no universal size for every fire alarm circuit. The correct size depends on the system design, load, cable length and voltage drop.

Is 1.5 mm² cable suitable for a fire alarm?

A 1.5 mm² cable can be suitable for some fire alarm circuits, but suitability depends on the circuit requirements, cable length, voltage drop, installation conditions and required fire performance.

What are the different types of fire alarm cable?

Common categories include standard fire resistant, enhanced fire resistant, screened and LSZH fire alarm cables. These characteristics can overlap so the complete cable specification should be checked before selection.

What is a 2-core fire alarm cable?

A 2-core fire alarm cable contains two conductors. The term 2-core describes the conductor count and does not by itself specify the cable's fire resistance, size or certification.

What is a Type 2 alarm cable?

Type 2 alarm cable is a classification associated with certain alarm and security cable specifications such as BS 4737. It should not be confused with a 2 core fire alarm cable.

Can fire alarm cable be run with data cables?

Fire alarm cable and data cables may require appropriate segregation or installation arrangements depending on the system and applicable requirements. The installation should be designed to avoid interference and maintain the required system performance.

What makes a fire alarm cable fire resistant?

Fire resistant fire alarm cables use specific conductor insulation, insulation materials, construction and protective layers designed to maintain circuit integrity under defined fire test conditions.