Method for evaluating effectiveness of surgical masks.

Greene, V. W. (University of Minnesota, Minneapolis) and D. Vesley. Method for evaluating effectiveness of surgical masks. J. Bacteriol. 83:663-667. 1962.-A portable isolation box, provided with a filtered air supply and a means of access for a test subject's head, was attached to an Andersen Sampler and used to measure orally expelled bacterial contaminants before and after masking. This technique yielded more detailed quantitative information than was obtained by either sedimentation plates or Andersen sampling in an unconfined space. During talking, unmasked subjects expelled more than 5,000 bacterial contaminants per 5 ft(3); 7.2% of the contaminants were associated with particles less than 4 mu in diameter. Masked subjects expelled an average of 19 contaminants/5 ft(3); 63% were less than 4 mu in diameter. Mask efficiencies varied according to particle size of the contaminants. This technique is adaptable for routine evaluation of an individual's contribution to environmental contamination.