As with all fire systems ASD's require regular maintenance, to ensure their continued performance and reduce the potential for false alarms. In many cases maintenance may be a legal requirement and while ASD's may be considered low maintenance they are not "no maintenance".
The frequency and method of maintenance should be clearly documented for each installation and determined by a risk assessment that should include consideration of at least the following:
- Equipment installed in dirty conditions will need to be checked more thoroughly and at more frequent intervals than that in clean and dry situations
- The class of the system
- Value or extent of the risk
- Detector technology employed
- Manufacturer’s recommendations
- Practicalities of performing maintenance/testing of sampling points.
Frequency of maintenance
Maintenance should be carried out at least annually. The routine to be adopted in individual premises may vary with the use of the premises.
Recommendations for routine Inspection and functional testing
ASD manufacturer’s instructions for maintenance and functional testing should be followed.
In general, the maintenance of an ASD system involves inspection/test of all elements of the system and with an overall functional test to ensure its continued performance.
Routine inspection
All fault and alarm output functions of the ASD should be tested where practicable and also any interfaces which may form part of the system. It is important to ensure that operation during testing does not result in an unwanted signal being sent from the ASD to another system.
Where ASD systems contain power supplies and battery back-ups these should be checked and tested in accordance with appropriate national Standards (e.g. BS 5839-1)
Any components fitted to the system with a defined operating life as defined by the manufacturer should be examined and replaced if necessary (e.g. filters, batteries).
It should be checked that there have been no unauthorized changes to the system configuration (e.g. sensitivity). If changes are required or have taken place, then these must be documented.
Any systems reliant on additional additives or consumables should be topped up in accordance with the manufacturer’s recommendations.
A visual inspection should be made to check whether structural, building or occupancy changes have affected the design requirements for the pipe-work and sampling points.
A visual inspection should be made of all sampling points, pipe-work, fittings, cables and equipment for secure fixing, appropriate labelling and for absence of damage and freedom from obstructions.
All systems must be functionally tested.
Functional tests
The objective of the functional test of a system is to ensure that the ASD and its associated pipe- work are still operational. This is ideally achieved by introducing smoke into each sampling point in turn and verifying a response at the detector. However where access is restricted or other conditions prevent this, other verification techniques should be employed such as:
- Verifying transport time from the furthest hole or a maintenance test point and comparing with the original and all previously recorded results to identify deviations
- Confirming that the flow monitoring is capable of detecting loss of a single sampling point or collection of sampling points that are deemed to be acceptable for the risks involved
- Inspection of flow readings and comparing with original and all previously recorded results to identify deviations that would indicate a loss of detection performance
- Measurement of the pressure at each sampling point and comparing with original and previously recorded results to identify deviations that would indicate a loss of detection performance
The technique used is dependent on the particular features of the ASD technology, the risk and the specific application and should be considered at the design stage (see section 8.6). Such techniques may also be supported by visual inspection of sampling points where this is possible but it is essential to verify that adequate detection performance is maintained. Details of the techniques used must be recorded and agreed with all parties taking the following points into account:
- Simulation smoke aerosol cans may leave residue if used to test ASD systems and / or particle lifetime maybe insufficient. Their acceptability needs to be verified by the ASD manufacturer
- The functional test carried out should not involve more than one sampling point at a time. Too large a test source is likely to affect more than one sampling point and invalidate the test results
- Differences in times to respond can indicate pipe-work and / or detection problems and / or changes to the pressure differentials between the protected areas. Response time differences should be investigated
- If the original commissioning time is not known or the acceptable deviation from it is not understood then all sample holes or groups of sample holes must be tested individually in accordance with the requirements of BS 5839-1: 2002. Where access to individual holes is restricted it may be necessary to clean the system and re-test in accordance with clause 14.2.3
- Where the ASD is specifically installed to provide early warning, regular repetition of the original commissioning performance smoke tests (clause 14.2.3.4) may be necessary to ensure that the original performance capability has not been compromised
- Many of these systems are installed in sensitive areas and permission is necessary even for the smallest amount of smoke / surrogate smoke. Where permission cannot be granted for a smoke test, other methods such as measuring the suction pressure at each sampling point, may be used to make an assessment of the system performance
User Responsibilities
Clause 47 of BS 5839-1: 2008 clearly identifies the need for the user of a fire detection and fire alarm system to appoint a person responsible for supervising “all matters pertaining to the fire alarm system”. It is especially important that a responsible person is appointed to supervise an ASD system, whether it is a “stand alone” system or an integral part of the overall building fire detection and fire alarm system.
As well as carrying out the general duties laid out in Clause 47 of BS 5839-1: 2008, the Responsible Person shall be trained in identifying potential environmental influences and situations which might affect the satisfactory performance of an ASD system, and actions which can be taken to overcome those problems. Problems may arise from:
- Changes to the use of the premises
- Changes to the layout of the premises
- Introduction of new processes or changes to existing processes
- Changes to the internal environment, such as installation of new air-conditioning
- Changes to the external environment, such as an increased level of background diesel fumes or increased levels of exhaust from another factory in close proximity
