Can the sensitivity of smoke detectors be tested with cigarette smoke?Back
Examination with cigarette smoke is not a suitable or accurate method to determine the sensitivity of fire alarm detectors. Special laboratory tunnels, which go through regular calibration, are used for this purpose. The tunnel regulates very accurately the amount of smoke and the rate of temperature rise, so that there are equal and stable conditions for the test of different detectors. On the basis of these tests and the EN54 standard which regulates detector sensitivity, a certificate is issued that confirms the appropriate work of the detector.
Comparing the sensitivity of fire detectors with cigarette smoke is inappropriate because:
1. In order for an accurate comparison to be made, we need to be sure there is equal amount of smoke particles in the air. This is impossible to be done by exhaling cigarette smoke, because the smoke chamber of one of the detector might be filled with more particles. The spreading of smoke particles in the air depends on the direction of exhaling, the force of exhaling, air currents, surrounding temperature and the position of the detectors. The inability for these parameters to be controlled outside of a laboratory makes it impossible for analysis to be made. One of the detectors may react earlier, but this is not a definite sign of higher sensitivity.
2. Even if the amount of particles in two different detectors happen to be the same, it is possible for them to react differently. This depends on the processing algorithm. For example SensoIris detectors by Teletek Electronics react if 4 consecutive measurements show smoke particles above the norm. Measurements are made every 4 seconds. If another detector has sample time more than 4 seconds or needs more than 4 measurements it will react later. The faster reaction with equal smoke particles means that it is more precise, not more sensitive.