A photocell smoke detector comprising a housing defining a dual section smoke chamber having a first smoke sensing chamber and a second compensating chamber, a smoke sensing photocell coupled to the smoke sensing chamber and a compensating photocell coupled to the second chamber, a light source coupled to the compensating chamber and transmitting a beam of light generally parallel and away from the photosensitive surfaces of the two photocells, and a light trap communicating with the smoke sensing chamber and fabricated of layers of corrugated media sandwiched between relatively flat liners whereby light is absorbed in the flutes of the corrugated media and smoke is enabled to pass freely into and out of the smoke sensing chamber.