Particle matter sampling method and sampler with a virtual impactor particle concentrator

摘要

An apparatus for sampling ambient air to obtain coarse and fine fractions of particulate matter includes a single acceleration tube and a collection tube coaxially arranged along a central axis with a gap between facing distal ends thereof within a range of d/D1 of 1 to 2, wherein d is the distance or gap between the distal ends and D1 is the inside diameter of the outlet at the distal end of the acceleration tube. A housing surrounding the acceleration and concentration tubes is provided with a side-wall nozzle connected to a suction device for drawing a major portion of the sampled ambient air therethrough and for separation of particulate matter, as a fine fraction, from that major portion. A second suction device draws a minor portion of the sampled ambient air, containing the coarse fraction of the particulate matter, in a straight path approximating the central axis, through the acceleration tube and through the collection tube for passage through a filter for separation of the coarse fraction of particulate matter. The ratio of the flow rates of the major and minor portions of the sampled ambient air is adjusted to provide a cutpoint within the range of 2-3 microns. The apparatus is preferably operated with a flow rate for the sampled ambient air within the range of 900-1200 liters per minute.