The Microdust Environmental Enclosure accessory to the Microdust Pro is designed to monitor aerosol or dust concentrations in either indoor environments where security is an issue, or in ambient conditions. Using the enclosure, it is possible to monitor a range of particle sizes (including PM10, PM2.5, respirable or TSP) for up to 24 hours. A filter collects all the sampled dust for gravimetric or chemical analysis and a "retrospective calibration" can be applied to the instrument.