The VRC* is EPA approved and a preferred method, for calibrating PM10 and hi-vol samplers (patent #3,944,153). This unit eliminates the drudgery of installing and removing five separate resistance plates during calibration. Simple rotation of the knob simulates the resistance of filters varying from clean to used. No removal of unit from the hi-vol is necessary until the data logging process is complete. Training time and error factor are reduced by employing this method.

The traditional hi-vol calibrator* requires manual changing of fixed resistance plates. This method offers an economical calibration technique where initial cost is a factor.