The BGI deltaCal is portable flow calibration/audit device which can be used for direct volumetric flow, barometric pressure and ambient temperature. The unit is NIST traceable. The deltaCal can be used to calibrate the BGI PQ100, BGI PQ200, or other samplers and pumps within its flow range. The BGI deltaCal is ideal for use in the field as it has no moving parts and works well with temperature extremes. The BGI DeltaCal replaces the BGI TetraCal volumetric continuous flow calibration/audit device.