BACKGROUND
For reliable functioning of Fire Alarm System a periodic test program is crucial. It is clear that testing cannot prevent failures but rather help on identifying failures so reducing downtime by promptly repair and replace, minimizing the time that property and people are left unprotected.
All components of every system are based on electronic components, so understanding its failure rates is worthwhile task. Based on the failure rates of electronics components, then failure rate for smoke detectors and other devices can be calculated. Failure rate is expressed in failures per million hours of operation (or its inverse, mean time between failure MTBF) and includes failures other than physical damage, dirt, dust or loss of power.
A good estimation of 3.5 failures per million hours applies to smoke detectors. So, testing once a year a detector could be out of service for 52 weeks undiscovered. From the table below, this average weeks is near 28 at 1 year operation. Furthermore, testing twice a year can drop this average weeks in half.
Testing a device, however, does not increase system reliability, rather identify failed units.
Different failure rates can be selected by design, selecting smoke detector model/brand accordingly. In any case, increasing the frequency of testing is the best way known to identify faulty units thus reducing system downtime. Even though modern systems have self-diagnostic features that may help identifying faulty units, only periodic test has proven to be an effective method recommended by applicable codes and standards, and not dependent of particular technology. Bear in mind that NFPA does not exclude alternative means for testing and encourages the use of equivalent methods, described in accordance between designer and local authority.
COMMISSIONING
All functions of the system has to be tested satisfactory in presence of the local authority, this has to be made right after installation or alterations. Every operation mode such alarm, trouble and normal condition shall be tested on every component, cable, initiating device and signaling appliance for proper response.
PERIODIC TEST AND MAINTENANCE
Smoke, Heat and Flame Detectors, should be inspected for missing parts, building modification, cleaned from dust and dirt and tested.
Audible and Visual Signaling Devices, inspected for missing parts, building modification, cleaned from dust and dirt and tested. All devices must be reseted as necessary.
Control Panel, every circuit must be tested on fault and alarm conditions following circuit style design performance. Power supply and backup batteries operation must be verified. All functions programmed in the control panel has to be verified as per cause-and-effect matrix.
Voice Alarm Communication, proper activation and intelligibility of voice messages through phone boxes, two-way telephones and speakers must be verified in each zone defined in system.
Manufacturer’s instructions must be followed for test and maintenance procedures applicable for each device and apparatus. Only qualified personnel must perform test and maintenance, local authority must witness.
Every device not performing accordingly must be replaced and re-tested. Written records must be furnished and signed by local authority after witnessing all tests activities. NFPA 72 contains mandatory minimum requirements of test type and frequency that must be complemented by system/building specific needs.
Recommended documents to keep in safe place:
As-built drawings
Operating instructions
System specifications
Battery and Voltage drop calculations
Cause-and-Effect matrix
Hard copy of system configuration program
Keys and passwords required
Reports of Acceptance, Inspection and Tests
References:
-NFPA 72, National Fire Alarm and Signaling Code
-UL 268 Smoke Detectors for Fire Alarm Systems
-R.W. Bukowski, “Fire Alarm Signaling Systems”
-DOD Military Handbook 217, Reliability Prediction of Electronic Equipment