A portable communication device may include a gas sensor enclosed in an enclosure, a port to allow flow of air into and out of the enclosure, and a light source disposed on an internal surface of the enclosure. The light source is operable to facilitate generation of ozone gas within the enclosure. The enclosure may contain a heating element that allows baseline calibration of the gas sensor by thermally decomposing ozone gas molecules. The gas sensor includes a miniature gas sensor such as a metal-oxide (MOX) gas sensor.