Functional checking is accomplished by introducing a smoke, or simulated smoke, stimulus from the protected area through the vents of a detector to the sensor(s).Functional checking of heat detectors, with a genuine heat source, is now required by major national standards around the world.

Testing with heat sources not designed for the purpose can be both dangerous and damaging. It is required by all national standards around the world and testing by electronic means that do not involve this test is not sufficient to comply.

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