Reduction of microbial concentration in air of dental operatory rooms by hepa filtration.

Microbial aerosols are known to be created and disseminated in dental operating rooms (DOR's) in quantities sufficient to raise the possibility of cross infection. The purpose of this study was to evaluate the effectiveness of high efficiency particulate air (HEPA) filters in reducing the concentration of airborne microorganisms. Tests were made in DOR's of 1600-, 1800-, and 3240-ft 3 capacity with an 800-cfm HEPA filter unit. Concentrations of microorganisms were measured 4 times daily at approximately 2to 3-hour intervals. Samples were taken in each DOR with 1-hour Reyniers air samplers drawing 1 cfm for 2 weeks without air filtration and then for 2 weeks with air filtration. In a DOR used for routine scaling with an ultrasonic instrument, the mean microbial air count of 21 viable particles (VP)/ft3 without air filtration was reduced 90 percent when the air was filtered. In this DOR, peak recoveries of 185 VP/ft3 without air filtration were reduced 84 percent when the air was filtered. Bacteria recovered during peak periods were predominantly alpha-hemolytic streptococci of the viridans group. In two DOR's used only for routine operative dentistry, microbial air counts were lower, with mean values of 3-8 VP/ft 3 and peak values of 8-26 VP/ft3 without air filtration. These concentrations were reduced 65 percent when the air was filtered. It was concluded that under normal working conditions an 800-cfm HEPA filter unit is effective in reducing the concentration of airborne microorganisms in a DOR by about 70 percent. Security Classification DOCUMENT CONTROL DATA R&D (Security claeificatlion of title, body of abstract and Indtexing annotation muet be entered when the overall report ta claeiil¢ .) 1. ORIGINATING ACTIVITY (Corporate author) 2a. UCPORT SECURITY C LASSItICATION Naval Dental School UNCLASSIFIED National Naval Medical Center 2b. •Roup Bethesda, Maryland 20014