A gas monitor comprising: a thin printed sorbent material (110, 120), comprising a printed sorbent ink with a binder, that is arranged to selectively adsorb a first target gas based on a concentration of the first target gas in a monitored environment; a second sorbent material that is arranged to selectively adsorb a second target gas based on a concentration of the second target gas in the monitored environment; a reference material (115, 125) that is not responsive to the first target gas and the second target gas; a first thermistor (120, 220) disposed within the thin printed sorbent material (110, 210), a second thermistor (125, 225) disposed within the reference material (115, 125), and a third thermistor disposed within the second sorbent material, wherein: the first thermistor (120, 220) is arranged to provide a first indication of a first temperature of the thin printed sorbent material (110, 120); the second thermistor (125, 225) is arranged to provide a second indication of a second temperature of the reference material (115, 125); and the third thermistor is arranged to provide a third indication of a third temperature of the second sorbent material; and a processing device (130, 230) arranged to: determine a concentration of the first target gas based at least in part on a differential measurement between the first temperature and the second temperature; and determine a concentration of the second target gas based at least in part on a differential measurement between the third temperature and the second temperature. a thin printed sorbent material (110, 120), comprising a printed sorbent ink with a binder, that is arranged to selectively adsorb a first target gas based on a concentration of the first target gas in a monitored environment; a second sorbent material that is arranged to selectively adsorb a second target gas based on a concentration of the second target gas in the monitored environment; a reference material (115, 125) that is not responsive to the first target gas and the second target gas; a first thermistor (120, 220) disposed within the thin printed sorbent material (110, 210), a second thermistor (125, 225) disposed within the reference material (115, 125), and a third thermistor disposed within the second sorbent material, wherein: the first thermistor (120, 220) is arranged to provide a first indication of a first temperature of the thin printed sorbent material (110, 120); the second thermistor (125, 225) is arranged to provide a second indication of a second temperature of the reference material (115, 125); and the third thermistor is arranged to provide a third indication of a third temperature of the second sorbent material; and the first thermistor (120, 220) is arranged to provide a first indication of a first temperature of the thin printed sorbent material (110, 120); the second thermistor (125, 225) is arranged to provide a second indication of a second temperature of the reference material (115, 125); and the third thermistor is arranged to provide a third indication of a third temperature of the second sorbent material; and a processing device (130, 230) arranged to: determine a concentration of the first target gas based at least in part on a differential measurement between the first temperature and the second temperature; and determine a concentration of the second target gas based at least in part on a differential measurement between the third temperature and the second temperature. determine a concentration of the first target gas based at least in part on a differential measurement between the first temperature and the second temperature; and determine a concentration of the second target gas based at least in part on a differential measurement between the third temperature and the second temperature.