An air monitoring system for analysing an air sample including: a duct arranged such that the air sample flows therethrough from an inlet to an outlet; a relative humidity sensor arranged to measure a relative humidity of the air sample; a heating module including a first heater arranged to heat the air sample; a temperature sensor arranged to measure a temperature of the air sample; a controller arranged selectively to operate the first heater if the measured relative humidity is above an upper threshold; and an analysis module including at least one chemical analysis transducer providing an output corresponding to a presence or concentration of a predetermined substance in the air sample.