A carbon monoxide (CO) detection unit incorporates a sensor which is a film or
layer of NixCo1-xOy where x is from 0.1 to 0.9,
e.g., spinel. The CO is detected by measuring the change in the electrical properties
of the sensor. The detector can measure CO concentrations below 100 ppm and is
capable of operating at room temperature and can be applied to domestic, industrial,
medical and vehicular use.