L2 Fire Alarm

L2 Fire Alarm

IS 2189 : 2008: Indian Standard. Selection, Installation And. Maintenance Of Automatic Fire. Detection And Alarm System

IS 11360 (1985): Specification For Smoke Detectors For Use In Automatic Electrical Fire Alarm System [CED 22: Fire Fighting]

A fire alarm system is number of devices working together to detect and alert people through visual and audio appliances when smoke/fire is present. These alarms may be activated from Smoke Detectors, Heat Detectors, MCP etc.

Smoke detectors do not have a listed spacing. They have a recommended spacing of 30 feet between detectors. However, smoke detectors can be installed up to 41 feet apart in corridors up to 10 feet wide. The main fact to remember is that all points on the ceiling must be within 21 feet of the detector.

Commercial systems are categorized as follows (All include manual call points):

·         L1 – Detection provided throughout the entire premises

·         L3 – Detection provided on all escape routes and adjoining areas

·       L3/L2 – Detection provided on all escape routes and adjoining areas, as well as additional detection in specified high risk areas

·         L4 – Detection provided on all escape routes only

·      L4/L2 – Detection provided on all escape routes and additional detection in specified high risk areas

When a system is installed in a premises where there is more than one interlinked system in operation, then the suffix “X” is used.

Many fire authorities are now insisting on specific standards of fire alarm systems within buildings.  These categories are defined in the recommendations of BS5839.  One of the most common categories which is being asked for is a BS5839 category L2 Fire Alarm System.  The prefix 'L' for the category type stands for life protection.  This means that the primary purpose of a category L2 Fire Alarm is to protect life.  Whereas BS5839 system designs with a 'P' prefix are primarily designed to protect damage to property.

L2 Fire Alarm Systems are designed to offer automatic detection on all escape routes within a building, with the addition of all rooms adjoining to the escape route.  An L2 Fire Alarm design should also take into account any further areas of high risk which may not necessarily be covered with detection on the escape routes and adjoining rooms.  Examples of these areas could be boiler rooms, plant rooms and other areas with heavy plant machinery (such as in roof voids).

An Example of an L2 Fire Alarm Design

L2 Fire Alarm designs should also incorporate audible sounders throughout the building which operate when the fire alarm system is activated.  These sounders should achieve a minimum sound pressure of 65 dB (A) throughout the building and a minimum of 75 dB (A) at the bedhead where there people sleeping within the building.

An L2 Fire Alarm should also include manual call points on all exits to open air, and in buildings above a single storey all entrances to stairwells on the floors above the ground floor.  In large buildings it should also be noted that nobody should have to travel for more than 35 metres to reach a call point.  This means that further call points may be needed to be positioned within the property to achieve this.  Call points may also need to be positioned in high risk areas.  One example of this may be a paint booth where high flammable substances are present.  A call point may need to be positioned in close proximity to enable an alarm to be raised quicker should an incident occur.

Awareness of the system user is also essential, less able bodied people may or may not be capable of exiting without assistance, but high levels of people with sporting injuries or with hearing difficulties may require a system which addresses their needs.