16.67 liters per minute is the equivalent 1 m3 per hour. The measurement principle is based on particles separated by size and collected in a filter. Therefore, the flow rate is set higher than human air intake in order to collect a quantity of particulate matter that is sufficient for a reliable and repeatable measurement.

Dear Ingo

Thanks for your comments.

Dear Marimuthu,

A sample flow of 16.67 L/min corresponds to 1.000 m3/hour volumetric flow rate. I believe this value was chosen back in 1971 when the US EPA first introduced a national air quality standard that required the measurement of PM10. One benefit of such a comparatively high flow rate is that it minimizes diffusion losses of the smallest particles and allows for a sharp cut-off curve at the upper limit for coarse particles.

Dear Oliver

Thanks for your answer.