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.