Patent ID: 7118272

Claim:
An apparatus for detecting a fire in an enclosed space, comprising: at least one thermally reactive element respectively arranged in said enclosed space and comprising a thermally intumescent material that undergoes an expansion in volume when heated above a trigger temperature; and an optical sensor arrangement arranged in said enclosed space and having an optical field of view encompassing said at least one thermally reactive element within said enclosed space, such that said expansion of said thermally intumescent material when said material is heated above said trigger temperature can be optically sensed by said optical sensor arrangement; wherein said at least one thermally reactive element comprises a plurality of said thermally reactive elements arranged in a dispersed pattern in said enclosed space with each respective element among said thermally reactive elements located at a respective unique distance and a respective unique angular position relative to a vertex of said field of view of said optical sensor arrangement so that each said element unambiguously links said respective unique angular position thereof to said respective unique distance thereof in said field of view.