Fire Alarm and Life Safety Systems
Code basis and Delaware review
Fire alarm work is governed by NFPA 72 and the adopted fire code. In Delaware, fire prevention is administered under 16 Del. C. ch. 66 through the State Fire Marshal, with local permits and inspections. Fire alarm contractors must confirm which license and permit apply before installing; low-voltage cabling alone does not authorize fire alarm system work.
Devices and circuits
An addressable or conventional FACP supervises initiating device circuits (IDCs) and notification appliance circuits (NACs). Class A pathways survive a single open; Class B does not. End-of-line resistors supervise conventional zones. Smoke detector spacing is commonly 30 ft (9.1 m) on a smooth ceiling, with 15 ft (4.6 m) from walls, but the manufacturer’s listing and ceiling height/beam rules control. Pull stations are located within 5 ft (1.5 m) of the exit door and no more than 5 ft above the floor.
Notification and audibility
Public-mode audible signals must be at least 15 dBA above the ambient sound level or 5 dBA above a sustained sound, whichever is greater, and not less than 75 dBA. They must not exceed 110 dBA at the minimum hearing distance. Visible notification must be synchronized when units are in the same field of view. Sleeping areas have lower limits and voice intelligibility requirements.
Worked example
A 24 V FACP must stand by 24 hours at 0.50 A and then alarm for 5 minutes at 2.0 A. Convert the alarm period to hours: 5/60 = 0.0833 h. Standby: 0.50 × 24 = 12.0 Ah. Alarm: 2.0 × 0.0833 = 0.167 Ah. Sum = 12.167 Ah. Apply a 1.20 safety/aging factor: 14.6 Ah. Select the next standard battery at or above 14.6 Ah, such as 18 Ah, after checking the charger’s recharge rating.
Traps
- Using 30 ft as a radius; it is a spacing dimension on the ceiling.
- Applying 15 dBA above ambient but forgetting the 75 dBA floor.
- Mixing Class A and Class B supervision.
- Sizing a battery without the 20 percent margin or without checking charger capacity.
- Treating a duct detector as a substitute for area smoke detection.