An apparatus comprising: a base plate for a passive infrared detector adapted for attachment via a rear surface to a wall; a pyroelectric element mounted to a front surface of the base plate, wherein the pyroelectric element is tilted downwards to receive and detect a predominant portion of energy from an area extending outwards and directly in front of the PIR detector and a relatively small portion of energy from an area directly below the PIR detector; a Fresnel lens mounted in front of the pyroelectric element that transmits the predominant portion of energy from the area extending outwards and directly in front of the PIR detector onto the pyroelectric element; a lookdown window mounted below the pyroelectric element that transmits the relatively small portion of energy from the area directly below the PIR detector onto the pyroelectric element; and a pivoting door having a first position and a second position mounted below the pyroelectric element between the lookdown window and the pyroelectric element, wherein the pivoting door pivots upwards to the first position so that the relatively small portion of energy is blocked and pivots downwards so that the relatively small-portion of energy is transmitted onto the pyroelectric element, wherein the Fresnel lens includes a cover that supports the Fresnel lens and the lookdown window, the cover being attached to a periphery of the base plate and extending outwards over the pyroelectric element, wherein the cover further comprises a flange extending partially around the Fresnel lens that supports the pivoting door, wherein the pivoting door includes a transverse shaft extending through the pivoting door that is supported by a flange, wherein the cover includes a pair of slots each of which is on an opposing side of the Fresnel lens and receives an opposing end of the transverse shaft via an interference fit, wherein each of the opposing ends of the transverse shaft comprises a rib extending outwards from a side of the transverse shaft, thereby engaging a marginal edge of each of the pair of slots, wherein each of the pair of slots includes first and second grooves extending into the marginal edge of a respective one of the pair of slots parallel to the transverse shaft, and wherein each of the first and second grooves engages a respective rib to retain the pivoting door in one of the first position and the second position. a base plate for a passive infrared detector adapted for attachment via a rear surface to a wall; a pyroelectric element mounted to a front surface of the base plate, wherein the pyroelectric element is tilted downwards to receive and detect a predominant portion of energy from an area extending outwards and directly in front of the PIR detector and a relatively small portion of energy from an area directly below the PIR detector; a Fresnel lens mounted in front of the pyroelectric element that transmits the predominant portion of energy from the area extending outwards and directly in front of the PIR detector onto the pyroelectric element; a lookdown window mounted below the pyroelectric element that transmits the relatively small portion of energy from the area directly below the PIR detector onto the pyroelectric element; and a pivoting door having a first position and a second position mounted below the pyroelectric element between the lookdown window and the pyroelectric element, wherein the pivoting door pivots upwards to the first position so that the relatively small portion of energy is blocked and pivots downwards so that the relatively small-portion of energy is transmitted onto the pyroelectric element, wherein the Fresnel lens includes a cover that supports the Fresnel lens and the lookdown window, the cover being attached to a periphery of the base plate and extending outwards over the pyroelectric element, wherein the cover further comprises a flange extending partially around the Fresnel lens that supports the pivoting door, wherein the pivoting door includes a transverse shaft extending through the pivoting door that is supported by a flange, wherein the cover includes a pair of slots each of which is on an opposing side of the Fresnel lens and receives an opposing end of the transverse shaft via an interference fit, wherein each of the opposing ends of the transverse shaft comprises a rib extending outwards from a side of the transverse shaft, thereby engaging a marginal edge of each of the pair of slots, wherein each of the pair of slots includes first and second grooves extending into the marginal edge of a respective one of the pair of slots parallel to the transverse shaft, and wherein each of the first and second grooves engages a respective rib to retain the pivoting door in one of the first position and the second position.