Model studies of directed sterile air flow for hospital isolation
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Design criteria for the achievement of effective forward and reverse isolation of hospital patients, with respect to airborne contamination, was developed through model studies of directed vertical sterile air flows. The essential requirements were found to be a low turbulent intensity (of the order of 1%) air column flowing downward at 60 feet per minute and returned through floor gratings about 12 in wide running the full length of the air column along the boundaries of the protected space. The width of the protected space was found to be slightly greater than the width of the air column. A ratio of the air flow collected and recirculated to the column air flow of 1.2 to 1.3 was found to be optimal. Boundary jets or'air curtains were found to be redundant and detrimental under some circumstances.
Methods used for the model evaluation were (1) flow pattern visualization using smoke traces, (2) velocity and turbulence measurements with a hot wire anemometer, and (3) isolation effectiveness tests using CO as a gaseous tracer to simulate airborne contamination.
KeywordsSmoke Turbulent Intensity Gaseous Tracer Turbulence Measurement Effectiveness Test
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