Incipient fire detector ii

Abstract

An improved incipient fire detector that employs a sub-micrometer size particle detector of the Wilson cloud chamber type in conjunction with a continuous on-the-fly sequential selector valve assembly and sample gas conduit system for monitoring a plurality of different enclosed spaces (zones). The sampling line for each zone can have up to ten heads, and delivers air or other gaseous atmosphere samples from the respective parts of the zone to the centrally located particle detector at a continuous flow rate of about 14 liters a minute. Each zone line is sampled sequentially by an electronically controlled selector valve assembly for a 15 second interval, once a minute. The cloud chamber particle detector operates at a cycling rate of about once per second and provides a continuous analog voltage corresponding to small particle concentration in the portions of the zone being sampled. The alarm sensitivity can be different for each zone and can be changed with time by means of an external timer to provide increased sensitivity at night, for example. A pre-alarm warning is provided for each zone with the alarm and warning states indicated by separate lights and alarm contact closures for each zone located at a centrally located control panel. The IFD incorporates several diagnostic circuits to monitor its operation, and in case of a problem a trouble indication is provided together with an indication on a diagnostic panel which shows the source of the problem.