Abstract: According to one embodiment, a hazard detector includes a front casing coupled with a back plate to define a housing having an interior region. The hazard detector also includes a passive infrared sensor device that is disposed within the interior region and that is positioned to face a room within which the hazard detector is positioned so as to detect objects within the room. The hazard detector additionally includes a Fresnel lensing component that is disposed on an exterior of the front casing and that is positioned in front of the passive infrared sensor device to direct infrared radiation onto the passive infrared sensor device. The Fresnel lensing component is configured to be inwardly pushable by a user to cause contact with a switch positioned therebehind so that input is provided to the hazard detector by the user.

Abstract: According to one embodiment, a hazard detector may include a back plate and a front casing coupled to the back plate to define a housing having an interior region and an opening through which air flows into the interior region. A circuit board may be coupled to the back plate and have a plurality of components mounted thereon. A smoke chamber may be mid-mounted on the circuit board, mid-mounting being characterized in the smoke chamber extending through a hole formed in the circuit board such that a top surface of the smoke chamber is positioned above a top surface of the circuit board and a bottom surface of the smoke chamber is positioned below a bottom surface of the circuit board, whereby an interior region of the smoke chamber is accessible to smoke from both the top and bottom surfaces of the circuit board.

Abstract: According to one embodiment, a hazard detector may include a housing having a back plate and a front casing coupled therewith to define an interior space within which various components are contained. The components may include an alarm device and a hazard sensor that is configured to detect a potentially hazardous condition to trigger the alarm device. A cover plate may be coupled with the housing and may face an occupant of a room in which the hazard detector is positioned. The cover plate may include a relatively large population of relatively small openings that are positioned, configured, and dimensioned so that internal components are substantially hidden from view of the occupant while air is allowed to substantially freely flow through the cover plate. A collective area of the openings may be at least 30% of the total area of the cover plate.