| Popis: |
This report summarizes the findings of four investigations of interactions of viable microbes with filter media. The first, challenging N95 filtering facepiece respirators (FFRs) separately with 800- and 100-nm latex and viral aerosols, showed experimentally that the media do not discriminate between inert and biological particles of either size. The second designed and built an artificial breathing system capable of operation at rates from 10 to 400 L/min, to complement an articulated headform separately generated. The third generated and delivered an aerosol of MS2 coli phage through an iodinated filter medium into 3-L plastic volumes prepared from food storage bags, incubated the aerosols for 1 to 10 minutes at room temperature and low, medium or high humidity, collected the aerosol in impingers containing thiosulfate to terminate the activity of iodine, plated the the contents of the impinger and measured viable MS2 counts on the plates. This showed that the half-life for viable MS2 airborne after exposure to iodine is 1 min---too short to be useful for FFRs, but of possible value in HVAC contexts. In the final study, volunteer cleaning staff members at a local hospital wore N95 FFRs while cleaning vacated patient rooms---the first study using humans as the collectors in an environmental study. Collection and plating of captured bacteria showed that the air clearance of fine particles is efficient, that a measurable viable population remains in the form of particles 10 micrometers, that the majority of the species assayed showed antibiotic resistance to oxacillin, and that 20 showed resistance to vancomycin as well. |
