Inspection, Testing, and Maintenance
Proving the system still works
ITM questions split into two families: the detection and releasing logic (NFPA 72) and the agent hardware (NFPA 2001, 12, 17, 17A, and the manufacturer's manual).
Recurring tasks:
- Container weight and pressure checks. Clean agent containers are weighed; a net weight loss greater than 5% requires recharge. High-pressure CO2 containers are recharged at more than 10% net weight loss.
- Enclosure integrity (door fan) testing at acceptance and again whenever the room is modified; uncontrolled openings are located and sealed.
- Releasing circuit testing. Exercise the panel, detection, notification, and release circuits, but never fire a live actuator. Use a test load or disconnect and secure the actuator per the manufacturer's procedure, then verify the sequence of operations.
- Kitchen systems. Inspect nozzles, caps, and piping; check the manual pull and fuel shutoff; examine the fusible link and actuation linkage (links are generally replaced, not cleaned); verify cylinder/cartridge condition and hydrostatic test dates.
- Full discharge tests are generally not repeated after acceptance; acceptance relies on a media (puff) test, flow calculations, and the door fan test.
Worked example: a container with a 100 lb net HFC-227ea nameplate weighs 94 lb at the annual inspection. The 6 lb loss is 6%, above the 5% threshold, so the container is removed, recharged to nameplate weight, and the cause of the loss investigated before the system returns to service.
Traps: passing a container that is "close enough" on weight; testing with actuators connected; skipping the re-test after a wall penetration is added; and assuming NFPA 25 frequencies apply to clean agent hardware.