Categories of
Fire Alarm Systems

Last Updated: June 29, 2022

There are two main categories of fire alarm systems; protection of life and property. Which one is best for you?

In existing commercial buildings, premises are subject to The Regulatory Reform (Fire Safety) Order 2005. The Order states that the ‘Responsible Person’ within the organisation has a legal duty to undertake a suitable and sufficient fire risk assessment at their premises. This assessment is a detailed report of the fire risk in your building, the adequacy of existing fire precautions, and the need for any additional fire precautions. The fire risk assessment will determine the level of fire alarm system required for your business premises.

What is meant by "categories of System"?

BS 5839-1:2017, the code of practice for designing, installing, commissioning, and maintaining fire detection and alarm systems in non-domestic buildings, contains recommendations for the locations of fire alarm system components based on the objective of the system should fulfil – known as Categories. These Categories are L and M for systems designed to protect life and Category P for those intended to protect property and it is very common, for a fire alarm system installed in a building to incorporate a mixture of Categories.

The brief guide below details classifications for commercial systems, we also have more information on domestic fire alarm systems.

Life protection

Life Protection will often depend on the number of people accessing a particular building and depending on variations, the systems can range from Type L1 to simple M categories.

Category l

Category L systems are automatic fire detection and alarm systems with the aim of protecting life. There are 5 levels within this category, each offering a different level of fire protection.

Category L1 Fire Alarm Systems

A Category L1 fire alarm system provides the highest standard for protection of life as they recommend both manual call points (MCPs) and automatic fire detection (AFD) be installed throughout the entire premises (including roof spaces and voids) to provide the earliest possible warning. Some areas need not be protected if they are of low fire risk such as stairways, lobbies, and small cupboards.

Typical installations for an L1 system include residential care premises and large office blocks.

L1 Fire Alarm System

Category L2 Fire Alarm Systems

A Category L2 fire alarm system is a further enhancement of protection to a Category L3 system but with additional detection in an area where there is a high chance of ignition. These areas can be identified following a fire risk assessment (FRA) undertaken by a competent person.

A Category L2 fire alarm system has automatic detectors installed in escape routes, rooms adjoining escape routes, and high hazard rooms e.g. kitchens, boiler rooms, plant rooms, sleeping risk, storerooms (if not fire-resistant) and is designed to give occupants as much time as possible to be evacuated before escape routes become impassable due to smoke and flames.

In medium-sized premises (sleeping no more than ten residents) a Category L2 system is ideal.

L2 Fire Alarm System

Category L3 Fire Alarm Systems

A Category L3 fire alarm system includes manual call points (MCPs) at defined positions and automatic fire detection (AFD) in all escape routes and rooms, corridors, and compartments that open onto escape routes of the protected premises. They are designed to provide warning to occupants beyond the room in which the fire starts so that they use escape routes before they are smoke-filled.

Category L3 systems provide more extensive cover than Category L4.

L3 Fire Alarm System

Category L4 Fire Alarm Systems

A Category L4 fire alarm system has manual call points (MCPs) throughout the building for occupants to manually identify a fire while automatic fire detection (AFD) should be installed along escape routes including stairwells. The reasoning behind this is to alert people of the danger before the corridor becomes ‘smoke-filled’ so people can escape safely.

Category L4 provides detection within the escape routes only, whereas Category L3 not only covers these areas but all rooms leading onto the escape route.

A Category L4 fire alarm system would not satisfy the requirements of legislation in buildings in which people sleep.

L4 Fire Alarm System

Category L5 Fire Alarm Systems

A Category L5 fire alarm system is for meeting specialist fire safety objectives, often in variation to the recommendations where strict adherence would not be possible. For example, such systems could include automatically closing metal shutters on a shopfront to contain the fire away from a shared concourse or computer rooms, which may be protected with an extinguishing system triggered by automatic detection. 

Often the requirement for a Category L5 fire alarm system is based on recommendations from a fire risk assessment (FRA) and should be provided as part of the fire system specification. This is a custom category and relates to a particular risk identified which warrants some special attention and special client requirements for their premises.

L5 Fire Alarm System

Category m

A Category M fire alarm system simply requires manual call points (MCPs) installed on all exits as well as corridors where persons are not expected to walk more than 30/45m to operate one and therefore incorporate no automatic detection. They rely on the occupants of the building to discover the fire and activate the system.

Such systems form the basic requirement for places of employment with no sleeping risk and are well suited to specific situations such as workshops or factories.

M Fire Alarm System

property protection

The objective of Category P is to provide the earliest warning of a fire to minimise the time taken from the ignition of fire to detection and the subsequent attendance by the fire services, minimising loss to the property.

category p

These types of systems are purely for the protection of property and fall into two classifications, Category P1 and Category P2.

Category P1 is designed to protect the whole building, Category P2 is installed in defined parts of the building only, which may have a high risk or hazard.

Category P1 Fire Alarm Systems

A Category P1 fire alarm system is designed to protect the entire building and offers the earliest possible fire warning. Detectors and alarms should be placed in all areas of a building so that the moment a fire breaks out the fire and rescue service can be alerted to stop the spread of the fire and minimize property damage.

A fire risk assessment (FRA) is helpful for designing Category P1 systems, as appropriate detectors will need to be installed in each room to cover the specific risks present

P1 Fire Alarm System

Category P1/M Fire Alarm Systems

The addition of /M does not stipulate that “some” MCP are necessary, it indicates that a full Category M system should be combined with a full Category P1 system. This means there should be AFD, MCPs, and alarm devices installed throughout the entire building.

Category P2 Fire Alarm Systems

A Category 2 fire alarm system provides fire detection in specified parts of the building where more specific coverage may be needed. For example, there is either high risk and/or where business disruption must be minimised and/or the contents are particularly valuable.

P2 Fire Alarm System

Category P2/M Fire Alarm Systems

The accompanying /M does not call for “some” MCP are necessary, it signifies that a full Category M system should be linked with a full Category P2 system. This means there should be AFD, MCPs, and alarm devices installed throughout the whole building.

Fire Risk Consultancy Services have the knowledge and experience to assist your business to comply with all legal requirements surrounding Fire Safety including the legislation regarding Fire Alarms. Be sure to read our accompanying guides: British Standards Relating to Relating to Fire Alarms,  A Guide to Fire Alarm System Types, Different Types of Fire Detector Heads, Fire Alarms in the Home, AND Fire Extinguishers, Emergency Lighting, Fire Door Regulations, Fire Safety Signs, also published on this site. 

Please take a moment to have a look around our website where you will find related articles and guides to all the services we can provide your business with, from providing fire risk assessments, fire safety training, advisory services to Articles on Fire Safety Provisions and our Top Fire Safety Tips!