Patent ID: 7884731

Claim:
A photoelectric smoke sensor for detecting smoke in a region, as well as its vicinities, where an optical axis of a light emitting element and a light-reception axis of a light receiving element cross each other, the photoelectric smoke sensor comprising: a casing member in which an internal space is formed by a labyrinth wall and in which an opening communicating with the internal space is provided on a setting-face side; and a printed board which is placed on the setting-face side having the opening of the casing member provided thereon and which has a hole opposed to the opening of the casing member, wherein the light emitting element and the light receiving element are mounted on the printed board in such a fashion that the optical axis of the light emitting element and the light-reception axis of the light receiving element cross each other at a point nearby the opening or within the opening in the internal space of the casing member and on one plane that is substantially parallel to an opening plane of the opening.