Techniques are described herein for air quality sensing. In some examples, the techniques are implemented as an apparatus including first and second light sources, a light detector having a detector output, and a processing circuit having a processing input coupled to the detector output and a processing output. The first light source is configured to generate a first light signal having a first wavelength. The second light source is configured to generate a second light signal having a second wavelength different from the first wavelength. The light detector is configured to generate a first detection signal at the detector output responsive to the first light signal and a second detection signal at the detector output responsive to the second light signal. The processing circuit is configured to generate a third signal representative of an air quality measurement at the processing output responsive to the first and second detection signals.