Spun glass air filters for bacteriological cabinets, animal cages, and shaking machine containers.

To minimize the chance of injury or disease from toxic or infectious substances, laboratory personnel are increasingly confining hazardous techniques to enclosed ventilated work cabinets. T'Ae well established use of the fume hood for chemistry has been extended to other laboratory sciences. The Atomic Energy Commission has been particularly active in this progress. The bacteriologist has recently become aware of dangers in techniques previously considered safe. Johansson and Ferris (1946) have demonstrated by high speed photography and air sampling that such operations as pipetting, pouring, and vigorous agitation of dilution blanks often produce bacterial contamination of the surrounding air and surfaces. Anderson et al. (1950) and others (Stein et al., 1949; Reitman et al., 1951; Stein and Rogers, 1946, 1950) have reported that flaming an inoculating loop, mixing broth cultures with a pipette by alternate suction and blowing, making microscopic slide agglutination tests, autopsy of infected animals, cooling a hot loop by immersing the loop in a culture, use of the lyophilizer, and other bacteriological manipulations release bacterial aerosols. A survey of laboratory acquired infections in the United States conducted by Sulkin and Pike (1950) tabulates a total of 1,334 infections presumably acquired in the laboratory. When a cabinet is used to confine accidentally released bacterial aerosols, it is desirable that the exhaust air be purified. Depending on the type of cabinet and volume of air, various methods may be used. One of the cheapest and most convenient is the use of spun glass' air filters. The use of spun glass as an efficient bacterial and viral filter has been reported by Decker et al. (1950). A one-inch layer was found to have an efficiency of 98 per cent or better in removing aerosolized clouds of Serratia indica and of Escherichia coli bacteriophage T-3. The readily available supply of spun glass, the low pressure drop across the filter pad, low cost, and the ease with which the spun glass can be installed in a filter frame suggested its use as a filter for bacteriological safety cabinets (Decker et al., 1951). A practical, compactly arranged, spun glass filter unit having a capacity up to 250 cubic feet per minute and an over-all resistance of 2 inches of water has been developed (figure 1). The over-all size of the filter cabinet is 2' by 3feet by 8 inches. Tests have been performed using S. indica and E..coli bacteriophage T-3 to determine the filtration efficiency.