A smoke alarm of radiation source and twin chamber design - has a shield around the intermediate electrode, built in various forms, to protect the ionisation chamber from air currents

摘要

A shield (22) is formed protruding from the isolator (6) into the ionisation chamber (B) of a smoke alarm. The shield (22) surrounds the periphery of the hole (3) in the intermediate electrode (2) and is manufactured of an insulating material. The remainder of the smoke alarm is an inner electrode (1), containing a radiation source, a printed circuit board (15), boardering an inner ionisation chamber (A), and an outer electrode (5). The outer electrode (5) surrounds the ionisation chamber (8) into which smoke can penetrate from the environment. -