isokinetic sampling
From Glossary of Meteorology
Any technique for collecting airborne particulate matter in which the collector is so designed that the airstream entering it has a velocity equal to that of the air passing around and outside the collector.
The advantage of isokinetic sampling consists in its freedom from the uncertainties due to selective collection of only the larger, less easily deflected particulates. In principle, an isokinetic sampling device has a collection efficiency of unity for all sizes of particulates in the sampled air.
