Selection, Installation and Maintenance of Control and Indicating Equipment for Fire Detection and Alarm System Code of Practice
2011 Edition

IS 15908 encompasses flame detectors, spark or ember detectors, aspirating smoke detectors, and other specialized types as specified by manufacturers or standards. Testing involves sensitivity checks according to manufacturer guidelines or Indian Standards, with at least 20% of detectors tested annually and all detectors assessed every five years. Heat and smoke detectors have specific clauses detailing their operational and visual inspections. Electrical tests are mandated every three years during annual inspections, with any faults recorded and addressed promptly to maintain detector accuracy throughout their service life.

The standby battery capacity is calculated using the formula: C_min = 1.25 × (T1 × I1 + (D × I2)/2), where T1 is the minimum 48-hour standby duration, I1 is the total standby load current, I2 is the alarm load current, and D is a derating factor (1 or 1.75 depending on battery type and manufacturer recommendations). This formula ensures batteries can support 48 hours of normal load plus 30 minutes at full alarm load, including a safety margin. Valve Regulated Lead Acid batteries are commonly used, with charging systems designed to restore capacity within 24 hours and provisions for voltage monitoring and automatic switching.

IS 15908 recommends Class A (loop) wiring for fire alarm circuits to maintain integrity in case of breaks, with Class B wiring used for tapping or conventional systems. Fire alarm cables should be segregated from other electrical circuits and preferably colored red for easy identification. Cable types include Fire Retardant Low Smoke (FRLS) PVC insulated cables with a minimum cross-section of 1.5 mm² for conventional systems, and shielded twisted pair cables for addressable systems. Mineral Insulated (MI) cables with Low Smoke and Fume characteristics are suggested for high-risk or critical environments. Proper mechanical protection and routing are essential.

Weekly functional tests are required, involving activation of at least one triggering device or end-of-line switch per zone to verify alarm signaling and transmission. For unmonitored wiring, each zone is tested weekly with a single alarm sound, whereas monitored systems with fewer than 13 zones require sequential weekly testing of each zone; systems with more zones test multiple zones weekly to ensure no zone remains untested for over 13 weeks. Visual checks on battery condition and connections are also conducted weekly, with immediate rectification of defects. All tests and faults must be recorded. Equipment placement must allow safe and easy access for maintenance.

Silencing fire alarm sounders or internal audio alarms requires manual operation of a silencing switch that activates a distinctive audible reminder near the control and indicating equipment, serving as an alert that silencing is in effect. Alarms do not automatically silence unless the system includes automatic reset functionality. If a new detector or manual call point activates in a different zone after silencing, the sounders must reactivate. Fire alarms can only be reset manually after silencing. The standard also outlines a two-stage alarm system where failure to acknowledge an initial alarm within about 60 seconds triggers a general evacuation signal.