Basic compliance
What is the standard to which fire alarm systems should comply?
I.S. 3218 is the standard for fire alarm systems in Ireland. This covers both commercial and domestic systems.
Am I required to have a fire alarm system?
Where you have a responsibility to provide a safe place of work and also have regular public traffic then you should ensure you have a fire alarm system.
Types of fire alarm systems
What is a conventional system?
Conventional fire alarm systems are a basic way of providing a fire alarm for protection.
An area is wired as a circuit (normally called a zone), starting at the control panel and ending at the last device. Smoke detectors, heat detectors and call points are placed on this circuit. A number of zones are required, depending on the building’s layout and size.
A system has up to 32 zones of detection. If an alarm occurs, the area affected shows up on the control panel in red L.E.D. The area then has to be searched to find out which device went into alarm – indicated by red L.E.D. on the device itself.
Detectors and call points are run on one circuit, while sounders utilise a separate circuit.
There is no way of programming devices to activate in certain ways, so the system provides a one in all out scenario.
What is an addressable system?
Addressable fire alarm systems are a more advanced way of providing fire alarm protection.
The area is wired as a loop, starting and ending at the control panel. Smoke detectors, heat detectors, call points, interfaces and sounders are placed on this loop. A number of loops might be required, depending on the building’s layout and size.
A system has up to four loops of detection. If an alarm occurs, both the location of the alarm and the affected device is indicated on the control panel. The device will also display a red indicator light to highlight its location.
Smoke detectors, call points and sounders can be run on the same circuit, which reduces installation costs.
What are the advantages of an addressable system over a conventional one?
Addressable systems are intelligent and allow staff to instantly identify the location of a fault or fire.
Example: Floor 2, Room 201, Loop 1, Address 24
They also involve less installation and are easier to maintain, as well as being more robust to false alarms. They allow the system to be programmed to match the client’s requirements.
Example: Should a fire be detected on the second floor of a three-storey building, an addressable system could be programmed so that only the doors on the second floor would release.
A conventional system in the same premises would only indicate the general area in alarm.
Example: Floor 2
This system does not allow for selective programming of outputs, so all outputs would be activated in the case of an alarm.
Example: All doors on all floors would release.
It stands to reason that addressable systems have a higher equipment cost, but they save on labour.
For a small facility, or one with a limited number of devices, a conventional system would suffice. Neither system is better at detecting a fire than the other, they just utilise different technologies.
It is important that, prior to installation, the system choice is discussed with the client. The system needs to be fit for purpose, taking into consideration the building’s layout and intended use.
What is the difference between a domestic and commercial system?
A commercial system has a control panel which operates and monitors all the installed detectors and sounders. It comes with a backup battery to ensure operation in the event of a power failure.
A domestic system normally consists of a number of interlinked mains-powered detectors with backup battery power. They operate independently of any control panel, but are interlinked (if one is in alarm they all are).
Are there different categories of domestic system?
Domestic systems are categorised under two headings: the grade of system (which details the equipment in operation) and the level of protection (which details where detectors are installed).
The LD2 system is the minimum Irish standard.
Grades of system:
- Grade F – Use of battery powered smoke/heat detectors
- Grade E – Use of interlinked mains-powered smoke/heat detectors, with no backup battery (the interlink can be hardwired, or radio-interlinked)
- Grade D – Use of one or more interlinked mains-powered smoke/heat detectors, each with a backup battery (the interlink can be hardwired, or radio-interlinked)
- Grade C – Use of smoke/heat detectors and sounders connected to a common system which includes mains and stand-by supply, with central control equipment
- Grade B – Fire detection and alarm system with detectors (other than smoke alarms), fire alarm sounders, control and indicating equipment
- Grade A – Fire detection system incorporating control and indicating equipment and power supply
Level of Protection:
- LD2 – Smoke/heat detectors installed in the dwelling on all circulation areas forming part of the escape route, as well as all high risk rooms
- LD1 – Smoke/heat detectors installed in the dwelling on all circulation areas forming part of the escape route, as well as all high risk rooms and other areas in which fire might start (other than toilets, bathrooms and shower rooms)
What are the categories of commercial system?
Commercial systems are categorised 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.
Sounder circuits
How many sounder circuits should I have in a building?
When standard conventional sounder circuits are used then a minimum of two circuits are required inside the building. This ensures that, should one circuit fail, there is a backup. This second circuit doesn’t need to provide the minimum sound level required throughout the building.
How many sounders should I have in a building?
It depends on the internal layout of the building and the type of sounders.
Generally, a conventional wall mount sounder will give an output of 105 decibels (dBA) when set to a high level, while sounder bases would be slightly lower. Once there is a door between a sounder and a person you will lose about 25 – 35 dBA, depending on the door type.
You require a minimum of 65 dBA above background noise. The use of beacons is allowed to visually indicate the alarm if high background noise is an issue.
In bedrooms 75 dBA is required at the bed head to wake a person, but this can be lowered in the case of healthcare institutions.
How high should I mount a sounder?
A standard sounder should be mounted 1.8m above the floor.
How high should I mount a sounder/beacon?
A standard sounder/strobe or individual strobe should be mounted 2.1m above the floor and not closer than 150mm from the finished ceiling.
Smoke detectors
What is the maximum distance between smoke detectors?
A smoke detector will provide coverage up to 100m² on a flat ceiling. However, a detector should not be more than 6m from any wall, or obstruction, and no more than 12m from another detector.
It may be necessary to have additional detectors fitted, depending on the building’s layout.
What is the maximum mounting height for a smoke detector?
A point type smoke detector should not be mounted on any ceiling exceeding 10.5m.
What is the maximum distance required between heat detectors?
A heat detector will provide coverage up to 50m² on a flat ceiling. However, a detector should be no more than 5m from any wall, or obstruction, and there should be no more than 10m between detectors.
It may be necessary to have additional detectors fitted, depending on the building’s layout.
What is the maximum mounting height for a heat detector?
An A1R heat detector should not be mounted on any ceiling exceeding 9m. For other types of heat detector the height should not exceed 7.5m.
How high should I mount my break glass units?
Break glass units or manual call points should be mounted 0.9 to 1.2m above the floor.
Cables
The type of cable required is detailed in I.S. 3218
It details the tests that a cable must pass, as well as offering advice on which cables are recommended for specific areas, ie PH30, PH60, PH120 Enhanced.
Where PH120 is specified on a job then the only cable that can be used is PH120 Enhanced.
Where burn rate cable is used it is recommended that you consult the designer, as well as the local fire authority.