An air quality sensor includes a detector element array, a processor operatively connected to the detector element array, and a memory. The memory is disposed in communication with the processor and has instructions recorded on the memory that, when read by the processor, cause the processor to execute certain operations including measuring electrical resistance of one of more detector element of the detector element array. A difference is calculated between the measured resistance and a reference resistance, and a determination is made of presence or absence of a contaminant in air communicated to the detector element array from an atmosphere of an aircraft cabin based on the difference between the measured resistance and the reference resistance. Aircraft and methods of monitoring air quality also described.