An air conditioning system, comprising: a unit receptive of a refrigerant having a moderate-to-low global warming potential, GWP, value for thermal interaction with a fluid; an enclosure comprising a main section surrounding the unit and having a vent, an outlet and an inlet, an exhaust duct leading from the outlet to the vent and a return-air duct extending from the exhaust duct to the inlet; a fan disposed and configured for urging a flow of the fluid through the unit; a refrigerant detection sensor disposed in the enclosure and configured to be operable in a first mode in which a baseline response is established and a second mode in which refrigerant leak detection is executed based on the baseline response; the refrigerant detection sensor being further configured to generate a binary output of leak and non-leak signals in accordance with a result of the refrigerant leak detection; and a control device and firmware configured to communicate to a main controller of the air conditioning system for operations of the fan and the vent based on the output; characterized in that: the refrigerant detection sensor comprises: a detection assembly; and an actuation assembly receptive of a signal from the detection assembly and configured for generation of the binary output based on the signal and for issuance of the binary output to the controller; the detection assembly comprises: an emitter; a detector; an optical element to reflect radiation emitted by the emitter toward the detector such that the radiation passes through an elongate section of the enclosure; and a band pass filter disposed along a radiation pathway between the emitter and the detector; and the detection assembly is configured to detect multiple types of the moderate-to-low GWP value refrigerant, and wherein a beam splitter is disposed along the IR radiation pathway to split the IR radiation into at least first and second beam components directed through corresponding first and second band pass filters and toward corresponding first and second detectors. a unit receptive of a refrigerant having a moderate-to-low global warming potential, GWP, value for thermal interaction with a fluid; an enclosure comprising a main section surrounding the unit and having a vent, an outlet and an inlet, an exhaust duct leading from the outlet to the vent and a return-air duct extending from the exhaust duct to the inlet; a fan disposed and configured for urging a flow of the fluid through the unit; a refrigerant detection sensor disposed in the enclosure and configured to be operable in a first mode in which a baseline response is established and a second mode in which refrigerant leak detection is executed based on the baseline response; the refrigerant detection sensor being further configured to generate a binary output of leak and non-leak signals in accordance with a result of the refrigerant leak detection; and a control device and firmware configured to communicate to a main controller of the air conditioning system for operations of the fan and the vent based on the output; characterized in that: the refrigerant detection sensor comprises: a detection assembly; and an actuation assembly receptive of a signal from the detection assembly and configured for generation of the binary output based on the signal and for issuance of the binary output to the controller; the detection assembly comprises: an emitter; a detector; an optical element to reflect radiation emitted by the emitter toward the detector such that the radiation passes through an elongate section of the enclosure; and a band pass filter disposed along a radiation pathway between the emitter and the detector; and the detection assembly is configured to detect multiple types of the moderate-to-low GWP value refrigerant, and wherein a beam splitter is disposed along the IR radiation pathway to split the IR radiation into at least first and second beam components directed through corresponding first and second band pass filters and toward corresponding first and second detectors. the refrigerant detection sensor comprises: a detection assembly; and an actuation assembly receptive of a signal from the detection assembly and configured for generation of the binary output based on the signal and for issuance of the binary output to the controller; the detection assembly comprises: an emitter; a detector; an optical element to reflect radiation emitted by the emitter toward the detector such that the radiation passes through an elongate section of the enclosure; and a band pass filter disposed along a radiation pathway between the emitter and the detector; and the detection assembly is configured to detect multiple types of the moderate-to-low GWP value refrigerant, and wherein a beam splitter is disposed along the IR radiation pathway to split the IR radiation into at least first and second beam components directed through corresponding first and second band pass filters and toward corresponding first and second detectors.