A gas monitor comprising: a thin printed sorbent material , 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 that is not responsive to the first target gas and the second target gas; a first thermistor disposed within the thin printed sorbent material , a second thermistor disposed within the reference material , and a third thermistor disposed within the second sorbent material, wherein: the first thermistor is arranged to provide a first indication of a first temperature of the thin printed sorbent material ; the second thermistor is arranged to provide a second indication of a second temperature of the reference material ; and the third thermistor is arranged to provide a third indication of a third temperature of the second sorbent material; and a processing device 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 , 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 that is not responsive to the first target gas and the second target gas; a first thermistor disposed within the thin printed sorbent material , a second thermistor disposed within the reference material , and a third thermistor disposed within the second sorbent material, wherein: the first thermistor is arranged to provide a first indication of a first temperature of the thin printed sorbent material ; the second thermistor is arranged to provide a second indication of a second temperature of the reference material ; and the third thermistor is arranged to provide a third indication of a third temperature of the second sorbent material; and the first thermistor is arranged to provide a first indication of a first temperature of the thin printed sorbent material ; the second thermistor is arranged to provide a second indication of a second temperature of the reference material ; and the third thermistor is arranged to provide a third indication of a third temperature of the second sorbent material; and a processing device 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. <EOS>