Abstract
Although the cascade impactor has been widely applied to the sampling of gently moving air streams as found in mine shafts or in the open atmosphere, only limited use has been made of it in ducts and stacks. An earlier duct probe design for the cascade impactor has been redeveloped, and a method has been found to prevent deposition of aerosol on the first stage prior to the actual sampling period. A control system has been devised which permits reproducible sampling periods as brief as 0.6 second.