Fire Alarm Installation

A category can also be described as an objective for the installation of a fire alarm system.

BS5839, both part 1 (Non-Domestic) and part 6 (Domestic) set out these objectives defining and describing the requirements and aims of a fire alarm system. 

These defined objectives (categories) allow the fire alarm designer to understand the desired outcome of installation and therefore meet these requirements.

For Example, Category L3 requires detection to be installed on the escape routes within a property. This allows the designer upon review of the building layout to know what areas require detection installed. 

There are the following categories of Systems defined in BS5839-1 2017:

BS5839-1:2017 in Non-Domestic Properties:

• L1
• L2
• L3
• L4
• L5
• M
• P1
• P2

BS5839-6:2017 in Domestic Properties:

• LD1
• LD2
• LD3

More specific information on each category can be found in our other FAQ's.

Under BS5839-6 2019 (For Domestic Properties) as well as categories there are also grades of systems.

These grades essentially advise the designer as to what type of system/detection should be installed.

The Grades are as follows:

• Grade A - A system that incorporates a Fire Alarm Panel and is installed in accordance with the requirements of BS5839-1:2017.
• Grade B - Fire Detection and alarm system utilising fire detectors, fire alarm sounders and a control indicating panel to either BSEN54-2or to annex C of BS5839-6. This was removed from the 2019 update to BS5839-6.
• Grade C - A system of fire detectors and alarm sounders (which may be combined in the form of smoke alarms) connected to a common power supply, comprising the normal mains and a standby supply, with central control equipment.
• Grade D1: A system of mains powered detectors with sealed tamper-proof backup batteries.
• Grade D2 - A System of mains powered detectors with user-replaceable batteries.
• Grade E - A system compromising of mains powered alarms without battery back up (stand by supply).  This was removed from the 2019 update to BS5839-6.
• Grade F1 - A system of battery-operated detectors with tamper-proof batteries.
• Grade F2 - A system of battery-operated detectors with user-replaceable batteries. 

The objective of an L1 system is to provide the earliest possible detection of fire to allow the longest available time for escape from a property. 

An L1 category design requires Automatic Fire Detection (AFD) & Manual Call Points (MCP) throughout the entirety of the premises.

Often specified for properties such as Hostels, Hotels, Hospitals, Shopping Centres, Residential Care Homes & Large complex properties.

The first step is to consult your Fire Risk Assessment. Part of this document will advise you which category ( & grade for domestic properties) of system you need to have installed to cover the premises. 

Our designers, provided with this information, will then determine the most suitable type of system & equipment for your property based on a wide range of factors. There is no "one size fits all" in terms of the type of equipment you need to be installed. This is based on what suits the specific property best in a various number of factors, such as cost, product compatibility, device suitability and even decorative appearance (for example in some buildings they require no cabling to be on show so a wireless system may be the best option).

Once provided with the requirements for the system our expert team of designers will guide you along the way and the following discussions will provide the best requirement to suit your and your properties requirements.

The objective of an L2 system is identical to that of an L3 system which is to protect the escape route of the premises to ensure it is clear for evacuation when required. 

However, L2 systems have the additional requirement to cover specified areas of high risk

The High-Risk areas should be determined by the Fire Risk Assessment and then covered by Automatic Fire Detection (AFD) to respond to reducing the risk of the escape route being blocked.

LD1 is often described as a "high level of detection".

This system would require detection installed throughout a dwelling, requiring detectors in all circulation areas that form part of the escape route and in all areas of the premises that a fire may start (excluding toilets and bathrooms). 

The objective of an L3 system is to provide a warning of a fire at an early enough stage to enable all occupants, excluding those possibly in the room of fire origin, to escape the premises safely before the escape routes become impassable.

The L3 category specifies Automatic Fire Detection (AFD) should be installed on the escape routes and all rooms which connect directly onto the escape route.

LD2, has been often referred to as "medium protection". This system would include detectors in all areas that form part of the escape route and in all rooms/areas that have a high risk of fire (For example, Kitchens). 

The objective of an L4 system is to improve the safety for occupants by providing of warning of a fire within the escape routes.

LD3 is the lowest level of detection required inside a dwelling.

Detection would only be required in circulation spaces that form part of the escape route for the property. 

The L5 category is designed for meeting specialist or unique fire safety objectives, often which vary from the "norm" where strict adherence to the requirements of the standard would not provide the optimal system.

L5 systems should be designed in conjunction with, and agreed upon by the relevant authorities before they can be signed off for installation.

An L5/M system should be designed to the full requirements of a category M system with the addition of automatic detection in required areas. 

Category M systems require no Automatic Fire Detection (AFD), rather it relies on the occupants of the building to raise the alarm by operating a Manual Call Point.

These systems will require Manual Call Points & Alarm Devices (Such as sounders, beacons, bells etc) installed throughout the property.

These systems are not often used to cover entire properties, rather specific areas of a property as part of a mixed category system. For example, the office area may have an L3 system and the warehouse or factory has a Category M system installed where occupants would likely notice a fire quicker than AFD would or where AFD could cause a high rate of false alarms.