An Improved Slit Sampler for Aerobiological Investigations

Abstract

The slit sampler described by Bourdillon, Lidwell, and Thomas (1) is based on impingement of particles on the agar surface of petri plates as air is drawn through a slit. Agar plates are rotated on a turntable with the agar surface 2 mm from the slit. By means of a laboratory pump 1 CFM (cubic ft. per. min.) of air is drawn through the apparatus, and the rate of flow is adjusted by a manometer. The sampler was designed for quantitative determination of numbers of bacteria in relatively quiet indoor air. The apparatus was found to be satisfactory also for sampling outside air and was used in aerobiological studies conducted by the author and Dr. C. D. Kelly at McGill University on the fungal and bacterial floras of the air. At first only petri-plates were used in the slit sampler, but it was discovered that silicone-coated slides could be used for sampling the air for fungus spores (3, 4, 5). When the author moved to Kansas State College in 1952, it was decided to continue aerobiological sampling with special emphasis on fungus spores of the air, the so-called spora according to Gregory (2), and particularly those of plant pathogens. Since the Bourdillon sampler is not available commercially, it was decided to construct a slit sampler. A sampler was constructed by D. A. Rittis of the Physics Department, Kansas State College, and is known as the PadyRittis modification of Bourdillon's slit sampler, or simply as the PadyRittis sampler. A description of the sampler is given in this paper with the technical details of construction in the appendix.