The nature and composition of experimental bacterial aerosols.

In the course of investigations on the effect of chemical vapors on air-borne bacteria, a better understanding of the state of the air-borne organism was sought through studies on the nature and composition of certain experimental bacterial aerosols. It was felt that an appreciation of the physical characteristics of the air-borne particle would add to our understanding of the factors which determine the life or death of the organism under various conditions. Such prior information as exists on this subject was reviewed by Wells (1955), much of it being from earlier work (Wells et al., 1948). Although the studies presented herein are concerned with experimental bacterial aerosols, the results obtained suggest that the findings are generally applicable to those arising from natural sources. We have previously described equipment and procedures for determining the effect of chemical vapors on the viability of air-borne organisms (Kethley et al., 1956). For the study of the physical characteristics of bacterial aerosols, a more complicated chamber system is required. Numerous chambers for the study of air-borne bacteria have been developed by other workers (Berry et al., 1949; Bourdillon et al., 1948; De Ome et al., 1944; Druett and May, 1952; Ferry and Maple, 1954; Griffin et al., 1956; Henderson, 1952; Kaye, 1949; Laurell et al., 1949; Leif and Krueger, 1950; Mackay, 1952; Phelps, 1942; Rentschler, 1942; Robertson et al., 1946; Rosebury, 1947; Twort et al., 1940; Urban, 1954; Weiss and Stegeler, 1952; Wells, 1955). However, none of these embodied all the desired features for the study of the nature and composition of bacterial aerosols. For this reason, the chamber which we have developed for this purpose is described in detail, and supporting data are offered to justify the use of this chamber in the detailed study of bacterial aerosols.