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.

How Should A Fire Alarm System Be Tested

How Should A Fire Alarm System Be Tested

We are often asked by customers "How Often Should A Fire Alarm System Be Tested?". The British Standard associated with fire alarm systems gives some recommendations as to when and how often a fire alarm system should be tested.

BS5839 recognises that although modern fire alarm systems incorporate a high degree of monitoring, so that faults are indicated at the control panel position, it is still necessary for a responsible person nominated by the user to ensure that fault indications at the panel are identified for appropriate action.  It is also impertitive for a regular test to be carried out to ensure that there has not been any major failure of the entire system, or significant part of the system.

How Often Should The User Test Their Fire Alarm System?

BS5839 recommends that the user / responsible person for the fire system tests their fire alarm system on a weekly basis.  The recommendations of the standard are as follows:-

1. Every week, a manual call point should be operated during normal working hours.  It should be confirmed that the control equipment (fire alarm panel) is capable of processing a fire alarm signal and providing an output to fire alarm sounders installed on the system, and if applicable to ensure that the fire alarm signal is correctly received at any fire alarm receiving centre to which fire alarm signals are transmitted.  It is not necessary to confirm that all fire alarm sounder circuits operate correctly at this time of the test.
2. The British Standard recommends that the weekly test carried out by the user should be carried out at approximately the same time each week.  Instructions to occupants should then be that they should report any instances of poor audibility of the fire alarm sounders.  In systems with staged alarms that incorporate an 'Alert' and 'Evacuate' alarm signal, the two signals should be operated, where praticable, sequentially in order they would occur at the time of a real fire event (i.e. 'Alert' and then 'Evacuate').
3. In premises in which some employees only work during hours other than at which the fire alarm system is normally tested, an additional test(s) should be carried out at least once a month to ensure familiarity of these employees with the fire alarm system singal(s).
4. A different manual call point on the system should be used at the time of every weekly test, so that all manual call points within the building are tested in rotation over a prolonged period.  There is no maximum limit for this period (e.g. in a system with 150 manual call points, the user will test each call point every 150 weeks). The result of the weekly test and identity of the manual call point should be recorded in the system log book.
5. The duration for which any fire alarm signal is given at the time of the weekly test by the user should not normally exceed one minute, so that, in the event of a fire at the time of the weekly test, occupants will be warned by the prolonged operation of the fire alarm devices.
6. Voice alarm systems should be tested weekly in accordance with the recommendations of BS5839-8.

Recommendations For Monthly Attention By The User Of The Fire Alarm System

Each month BS5839 makes the following recommendations upon the monthly attention on a fire alarm systems each month if applicable.

1. If an automatically started emergency generator is used as part of the standby power supply of a fire alarm system, it should be started up once each month by simulation of failure of the normal power supply and operated on-load for at least one hour.  The test should be carried out in accordance with the instructions of the generator manufacturer, including instructions on the load that should be operated.  At the end of the test, the fuel tanks should be left filled, and the oil and coolant levels should be checked and topped up if necessary.
2. If vented batteries are used as a standby power supply, a visual inspection of the batteries and their connections should be made to ensure that they are in good condiction.  Action should be taken to rectify any defect, including low electrolyte level.

Note:  Care should be taken to ensure that any person undertaking these monthly tasks is competent to do so safely and has the relevant technical knowledge and training.

BS5839 Part 6 2004 - Fire Alarm System Installations in Dwellings

BS5839 Part 6 2004 - Fire Alarm System Installations in Dwellings

The British Standard Associated with Fire Alarm System Installations in Dwellings is BS5839 Part 6 2004.  This part of the British Standard is split up into 3 categories of systems.  These categories are as follows:-

• LD1 - Alarms in all circulation spaces that form part of escape routes and all areas where a fire might start, but not bathrooms, shower rooms or toilets
• LD2 - Alarms in all circulation spaces that form part of escape routes and rooms or areas that present a high fire risk
• LD3 - Alarms in circulation spaces that form part of escape routes

The category of system that should be installed in a building is often defined by Councils, Insurance Companies, Fire Officers, Building Control and many others.

The above categories indicate the category of system that should be installed.  Further to this information different grades of system may be specified.  

These are as follows:-

• Grade A - A full system with control and indicating equipment installed to BS 5839: Part 1
• Grade B - Detectors and sounders using simpler specified equipment
• Grade C - Detectors and sounders or alarms with central control
• Grade D - Mains powered alarms with an integral stand-by power supply
• Grade E - Mains powered alarms with no stand-by power supply
• Grade F - Battery powered alarms

These grades are used in conjunction with the category type, to indicate what type of system should be installed within the property.  For example if an LD2 Grade A system is requested, this would require a system with alarms in circulation areas that form escape routes and high fire risk areas with the equipment with control and indicating equipment compliant to BS5839 Part 1.