Monitoring pollutants in air, soil and water is a routine requirement in the workplace, and in the wider environment. Passive samplers can provide a representative picture of levels of pollutants over a period of time from days to months by measuring the average concentrations to which they have been exposed. Air monitors are widely used, for instance to measure the exposure of workers to volatile compounds, but also for monitoring the fate of pollutants in the atmosphere. Passive sampling devices are now becomining increasingly used to monitor pollutants in rivers, coastal waters and ground water where contamination results from sources such as domestic and industrial discharges, and the use of agrochemicals.