Potential problem with Heat Detectors

Wednesday, December 1, 2010

Recently one of our members had a small fire in a lab garbage can during the night time hours.  Fortunately the fire burnt itself out and was discovered the next morning.  The 135 F fixed temperature heat detector above the fire location did not activate and when tested by the university using a heat gun it was found to be defective.  The university only had one replacement detector so a  similar detector in an adjacent lab was tested and found to be okay.  The university did not feel that testing two detectors provided sufficient data and decided to order six replacement detectors and conduct tests on the existing detectors.  It should be noted that the heat detectors are not restorable upon testing with heat.  The annual testing required by fire code only calls for verification of the electric signal from the detector.  Upon receipt of the six new detectors the old detectors were tested using a heat gun and none of the detectors operated.  The university immediately decided to remove and replace all their heat detectors.

The detectors were manufactured by Edwards and are from 1982. (See attached photograph). The detectors are supposed to be good for up to 50 years.   The university is recommending to others that if you have  similar heat detectors that you begin a program of randomly replacing and testing in order to have some assurance that they will work when needed.

February 2011 Update

A total of 20 heat detectors that were removed from the university were sent to a test facility.  Only one device successfully passed the testing based upon the manufacturer's guidelines.  Twelve of the 135 F heat detectors failed to operate even when test temperatures reached 300 F.

The heat detectors are Edwards N283A Fixed Temperature 135F ULC Issue #2479C.  Anyone who has these detectors is encouraged to develop a system of periodic testing and replacement of such devices.