Posted By stevehaigh Could anyone tell me what is the difference between optical alarms and ionisation alarms? Also how do you identify smoke alarms from heat alarms?

Posted By Ashley Wood Ionisation detectors use a radio active source i.e. americium. They are used where smaller smoke particulate may be present i. e computer room, switch room, electrical area, etc. and are sensitive to levels of 'light' smoke. Optical detectors are basically a light chamber, this is where an LED projects a light beam to a receiver on the other side of the chamber, but between the 2 is a bridge or low wall. The light hits the bridge and is prevented from reaching the receiver. However, should large smoke particulate enter the chamber then light bounces off it and eventually reaches the receiver and an alarm is rased. This type of detector is used in areas where denser smoke is likely. Typical sensitivity of a smoke detector is around 4 % obscuration per meter, but the sensitivity decreases with time. If you want to remove an ionisation detector then it has to be disposed of correctly. There are 2 types of heat detector, rate of rise and fixed temperature. Fixed temperature should always be used in kitchens as it will not be effected by changes in temperature as the alarm level is 'fixed.' Then there are other types of systems i. e air sampling, UV, IR, beam, etc., etc. Thats another story!