In order to achieve maximum benefit from a fire detection system in the event of genuine fire activation, the fire services need to attend as quickly as possible. In many cases this is carried out satisfactorily by the occupants dialling 999. However, an automatic signalling system is likely to be of benefit if the size/complexity of the building or low level of occupancy may result in significant delay between discovering a fire and notifying the fire and rescue services.
When should you consider adding automatic signalling to a fire alarm system and what is a monitored system?
Monitored systems provide automatic transmission of a fire condition signal to a specified monitoring station or Alarm Receiving Centre. The aim is the same whether called a Monitored System, a Signalling System or an Automatic Transmission System.
There are many obvious benefits:
- Ensuring business resilience in the event of a fire outside of the premises opening hours
- Overcoming the difficulty of occupants who are unsure of or are unwilling to follow correct procedures
- Improve maintenance services by including system ‘Fault’ monitoring
BS5839 helpfully lays out certain aspects which should be considered carefully as follows.
When is a Monitored Signal required?
If, in order to ensure the safety of occupants, it is considered critical that the fire and rescue services are called at an early stage, then a system to give automatic transmission of alarm signals should be provided. This critical aspect may be indicated following a risk assessment or due to other inadequate arrangements to summon help.
Certain applications require an automatic signalling system:
- In residential care premises, facilities should be provided for automatic transmission of alarm signals to an Alarm Receiving Centre.
- Except for continuously occupied premises, Category P systems should have automatic signal transmission to an Alarm Receiving Centre.
- In non-domestic premises in multiple occupation, Category L systems should incorporate an automatic means for transmission of alarm signals to an Alarm Receiving Centre, unless there are arrangements in place for summoning the fire and rescue service by occupants of the building, at all times that the premises are occupied (or partly occupied).
What are the key tasks to be considered?
If a Category L or P system incorporates an automatic signalling system, any critical areas such as telephone switch rooms or similar must be protected by automatic fire detection or an automatic fire extinguishing system.
As far as reasonably practicable, cables within the building (including telephone lines) should be routed through areas of low fire risk or be routed through areas protected by automatic fire detection or an automatic fire extinguishing system and these cables should be of standard or enhanced fire resistance.
Signalling should not be prevented by silencing the fire alarm sounders, i.e. it is not suitable to connect a relay to the bell circuit: a suitable Fire Protection output should be used which clears on RESET rather than SILENCE.
If the signalling unit is mounted in a separate enclosure from the fire alarm (as it usually is) then the connection to the signalling unit should be monitored.
Consider a suitable means to disable the signalling system for test purposes, i.e. the installation of a keyswitch. However, be aware that a disabled signal may be accidentally forgotten, so ensure that the disablement action also generates a disablement or a fault warning at the main control panel.
Discuss with the client and any other interested parties whether filtering may be implemented, i.e. if staff are present there may be a time delay for them to investigate any incidents before the automatic signal transmission takes place.
How does this affect a system installer?
Ensure that you have a current copy of BS5839 Part 6 2013 for the relevant details. This will ensure that you capitalise on any additional business with signalling systems in a safe and compliant manner.
The next port of call is always to ask your supplier to recommend the best product for your requirements. Most good suppliers will have their own technical support teams for this purpose and will be quite used to each situation.
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