A type of gravimetric method to measure particles that draws air at a known flow rate through a pre-weighed filter for 24 hours. Particles in air are collected on the filter which is then weighed in a laboratory and reported as micrograms per cubic metre. Partisols operate a cassette system that contains multiple filters that can automatically be changed at a pre-determined time. While the automated filter exchange can make this method more practical than the High Volume Sampler for NES-AQ compliance monitoring, the laboratory “turn around” time for obtaining particulate concentrations means that there can be limitations around the ability to report PM10 exceedances within the one month timeframe required by the NES-AQ.