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When Testing, Why Isn't the LED Lit Continuously?

To properly test a smoke detector, use canned smoke or the smoke that the manufacturer recommends. Magnets do not test for smoke.


Hi Douglas,

Hope you are doing well. What can you say about the addressable smoke detectors that when activated with solo spray, the alarm is received at the panel, but the LED lamp is not getting lit continuously?

Normally light blinks every 5 sec. but during the activation blinks every 1-2 sec. or sometimes 2 times in 1-2 secs. And then when the alarm is received at the panel, it is getting back to 1 time in 5 sec.

Thank you, A L

First off, that blink you are seeing on the smoke detector is the time that the fire panel is communicating with that particular detector. Normally, every 5 seconds or so the panel is checking with each detector and module in the system to make sure all are connected, and to receive any alarms or troubles in the system. This check of the detector every 5 seconds is called "Polling" (asking the detector).

When you spray smoke into the detector, the panel receives the "smoke-is-detected" signal from the detector. Because the panel has received the "smoke-is-detected" signal from the detector, the panel starts checking the detector every 1 or 2 seconds, using a "fast-check" polling.

Walk Test

It sounds like you are testing the smoke detectors while the system is in "walk-test". When the system is in walk test, you are testing to see if the panel receives a signal from the detector.

Each manufacturer has a different method of checking the building's alarm devices while in the walk-test mode. To find out if what you're experiencing is normal, you will have to talk to the Technical Support Team at the manufacturer. They can tell you if what you see is normal for this model of fire alarm system.

Keep in mind some things about testing fire alarm systems. The walk-test mode doesn't tell you what the panel is going to do once it receives an alarm. To find out what the panel does in real life, you have to leave the system as it was before you arrived and see what happens when smoke is detected. This is the "Live Method" of testing the fire alarm system. You can test the smoke detectors themselves in the walk-test mode, but the "Live Method" is required to find out if the whole fire alarm system works. That's what you are there for in the first place.

When you test using the Live Method, the horns and strobes should turn on, starting the evacuation of the building. And if you haven't called the off-site monitoring company so they won't take any action during the testing, the fire department should also arrive. (You don't want to see the fire department, so put the system on test with the monitoring company before any testing.)

After testing, call the monitoring company again to find out if they did receive the alarms that you sent their way. That call is required to complete the testing.

Canned Smoke versus Magnet

You are using smoke to test the detector. Whereas many smoke detectors can be "tested" using a magnet, most fires do not carry magnets around in their back pockets. Testing with a magnet doesn't show you if the smoke detector will detect smoke. Keep using the smoke; use smoke tests (even canned smoke) to see if the smoke detector will detect smoke.

See http://www.douglaskrantz.com/Blogmagnettesting.html to find out about my experiences with testing using magnets.

Douglas Krantz
Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer

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