THE DETECTION OF AIRBORNE POLLUTANTS

摘要

A smoke detector (2) which operates on the scattered light principle comprises a detector chamber (4) through which a light beam (10) passes. A series of collimator discs (24, 26, 28) with apertures of progressively increasing size are associated with the light source (6) to prevent glints of light from entering the zone of the chamber at which detection occurs as a result of the presence of scattered light induced by the presence of smoke particles. A light absorber (12) at the end of the detector chamber remote from the light source uses a target surface in the form of an asymmetric cone (42) onto which the beam is directed. The design of the collimator discs and light absorber reduce the occurrence of stray light, leading to increased sensitivity.