Abstract: A method for controlling an air sampling pump includes establishing from empirical measurement a family of sets of data relating speed of the pump to the flow rate of air through the pump as a function of pressure drop of the air at the pump inlet and storing the data in an electronic memory. The pump is then operated at a selected speed corresponding to a desired air flow rate and selected inlet pressure drop. The actual pressure drop is measured and a pair of sets of pressure drop values are identified in the stored data, which values bracket the actual measured pressure drop. The desired air flow rate and corresponding pump RPM value for each of the identified pair of sets of differential pressure values are located and extrapolation is used to locate a new value of RPM for delivering the desired air flow rate at the actual measured value of pressure drop. The pump is then operated at the new RPM value.