Aerosol detection device

Abstract

Fire alarm system utilizing an aerosol detector of the type formed by outer and inner interconnected ion chambers with a single particle source located within the inner chamber. The particle source radiates charged particles emitted therefrom into the inner chamber as well as through the path of chamber interconnection into the outer ion chamber. The outer chamber communicates directly with atmosphere to be monitored and operates as a sensing ion chamber. The inner chamber, operates as a reference ion chamber, is only interconnected with the outer chamber, and is otherwise totally isolated from outside atmosphere to avoid contamination of the particle source therein. Two embodiments of aerosol detector are disclosed. The first has a radiation permeable, aerosol impermeable dielectric film, made of a material such as Mylar, Teflon or the like, mounted as a barrier across the path of chamber interconnections to permit charged particles emitted from the particle source to pass essentially uninfluenced therethrough while isolating the inner chamber from smoke and combustion aerosols to prevent contamination of the particle source. The dielectric film also provides a physical barrier which prevents a detached particle source from falling out of the inner chamber. The second embodiment is like the first with the addition of a second similar type dielectric film which covers over the particle source itself. The second film improves the operation characteristics of the device as well as providing an additional physical barrier to hold the particle source in place. A third embodiment provides for selective positioning of the radioactive source and a collector electrode in the outer chamber.