A smoke detector comprising: a housing including a base, the base including a planar surface configured for being positioned against and attached to a ceiling, a printed circuit board comprising a substantially planar shape with a front surface and an opposing back surface spaced in a thickness direction T, and a plurality of perimeter edges including a bottom edge and an opposing top edge spaced in a height-wise direction H, a first side edge and an opposing second side edge spaced in a transverse direction, wherein; the top edge comprises a first projection extending in the height-wise direction away from the top edge, the first projection including a first temperature sensor height-wise spaced from the top edge, and the PCB is mounted to the housing so that the front surface of the PCB is perpendicular to the planar surface of the base, and the first projection extends away from the planar surface of the base; the top edge of the PCB includes a first segment which is transversely intermediate the first side edge and the second side edge, the first segment having a profile shape that defines a cutout area in the planar shape of the PCB, the first top segment of the PCB includes a first transverse end proximate the first side edge of the PCB, the first transverse end comprising the first projection extending in the height-wise direction away from the first top segment; the first top segment of the PCB includes second transverse end that opposes the first transverse end and is proximate the second side edge of the PCB, the second transverse end comprising a second projection extending parallel to the first projection, wherein the smoke detector includes a plurality of temperature sensors including the first temperature sensor and a second temperature sensor, and wherein the second projection includes the second temperature sensor. a housing including a base, the base including a planar surface configured for being positioned against and attached to a ceiling, a printed circuit board comprising a substantially planar shape with a front surface and an opposing back surface spaced in a thickness direction T, and a plurality of perimeter edges including a bottom edge and an opposing top edge spaced in a height-wise direction H, a first side edge and an opposing second side edge spaced in a transverse direction, wherein; the top edge comprises a first projection extending in the height-wise direction away from the top edge, the first projection including a first temperature sensor height-wise spaced from the top edge, and the PCB is mounted to the housing so that the front surface of the PCB is perpendicular to the planar surface of the base, and the first projection extends away from the planar surface of the base; the top edge comprises a first projection extending in the height-wise direction away from the top edge, the first projection including a first temperature sensor height-wise spaced from the top edge, and the PCB is mounted to the housing so that the front surface of the PCB is perpendicular to the planar surface of the base, and the first projection extends away from the planar surface of the base; the top edge of the PCB includes a first segment which is transversely intermediate the first side edge and the second side edge, the first segment having a profile shape that defines a cutout area in the planar shape of the PCB, the first top segment of the PCB includes a first transverse end proximate the first side edge of the PCB, the first transverse end comprising the first projection extending in the height-wise direction away from the first top segment; the first top segment of the PCB includes second transverse end that opposes the first transverse end and is proximate the second side edge of the PCB, the second transverse end comprising a second projection extending parallel to the first projection, wherein the smoke detector includes a plurality of temperature sensors including the first temperature sensor and a second temperature sensor, and wherein the second projection includes the second temperature sensor.