Smoke detector sensitivity testing: measured, not sprayed
Canned smoke proves a detector responds. It does not prove it is in calibration. Here is the schedule, and how the longer interval is earned and lost.
Two different tests get called the same thing. A functional test proves a smoke detector responds to smoke. A sensitivity test proves it responds at the right level. NFPA 72 Chapter 14 requires both, and they are not interchangeable.
Sensitivity has to be measured
Blowing an unmeasured aerosol at a detector proves it responds to smoke, not that it is in calibration. Sensitivity is checked against the detector's listed and marked sensitivity range. Where a detector carries no marked range, the reference is 4 percent obscuration light grey smoke.
From the field
Canned smoke is a functional test, not a sensitivity test. The two get confused constantly.
The schedule
| Stage | When sensitivity is checked |
|---|---|
| New installation | Within the first year after installation. |
| After that | Every alternate year. |
| After two consecutive passing calibration tests | The interval may be stretched to a maximum of 5 years. |
| Any zone where nuisance alarms increased over the previous year | Calibration tests are performed regardless. |
This schedule does not apply to one and two family dwellings.
The 5 year interval is earned, and it can be lost
The longer interval is not a choice. It is earned by two consecutive calibration tests showing the device inside its listed and marked range. Once it is in use, records of nuisance alarms and the trends in them have to be maintained. In any zone or area where nuisance alarms show any increase over the previous year, calibration testing comes straight back.
That means the nuisance alarm log is part of the testing program. A site on the extended interval with no nuisance alarm records is not meeting the condition that comes with it.
Detectors you cannot safely reach
Devices that are inaccessible for safety reasons, such as continuous process operations, energized electrical equipment, radiation or excessive height, may be tested during scheduled shutdowns if the AHJ approves. The extended interval cannot exceed 18 months.
The test is safety, not convenience. A detector that is merely awkward to reach does not qualify, and the AHJ approves the arrangement, not the contractor.
Duct detectors
Under NFPA 72 Chapters 14 and 17, a duct detector has to be accessible for cleaning, with access doors or panels provided for the purpose, and the location of every duct detector is permanently identified and recorded.
From the field
A duct detector 30 feet up over a mechanical room with no access is a finding waiting to happen.
Who does the work
Under NFPA 72 Chapters 10 and 14, service personnel are expected to understand the alarm code and the electrical code, the equipment, and the test methods, and to be able to read the system documentation. This is the clause behind certification requirements in most jurisdictions.
Keep reading
Manual pull stations: placement, height and travel distance
Measure to the handle, put one by every exit, then walk the floor to check nobody is more than 200 feet from one.
Fire department access: the address, the road, the hydrant, the key box and the FDC
Everything inside the building depends on the fire department getting to it. Five things to check from the street before you walk in.
Fire alarm audibility: sound levels, ambient measurement and the evacuation signal
A horn passes or fails against the room it is in, not its data sheet. Measure the ambient first, then check the margin, the ceiling and the signal itself.
Waterflow and supervisory signals from the sprinkler system
The 90 seconds is the device, not the horns. What the waterflow and supervisory devices have to do, and how many go on one circuit.
Fire doors: self closing, latching and what actually voids the label
A door that closes but does not latch has lost its rating. Not every hole drilled on site has, and the listing laboratory is who decides.
Strobe mounting height and candela: how NFPA 72 sizes visible notification
Measure the lens, size the room correctly, and never drop a strobe below 80 inches without redoing the coverage.