Circulation in sanitary ventilation by bactericidal irradiation of air

Abstract

1. 1. An improved method of measuring sanitary ventilation has been developed. The average lethal exposure of air-borne infection between occupants of enclosed spaces measures air disinfection in terms of ventilation, a lethe of disinfection becoming the sanitary equivalent of an air change of ventilation. 2. 2. Lethal exposure of E. coli, atomized into dry air, to 2537 Å radiation, has been revaluated. Exposure to .002 watt minutes per square foot, or .002 foot watt minutes per cubic foot of uniform irradiation, gives a lethe of disinfection, equivalent to an air change of ventilation. One foot watt minute of uniform irradiation becomes the sanitary equivalent of 5oo cubic feet of fresh dry air. 3. 3. The sanitary equivalent of irradiation of recirculated air has been formulated. Sanitary ventilation approaches recirculation as disinfection increases, and uniform irradiation of the room as recirculation increases. Recirculated air, to provide the approximate sanitary equivalent of fresh air, must be exposed to at least five times the direct irradiation in a room providing equivalent sanitary ventilation. 4. 4. This formulation may also be applied to equivalent recirculation by indirect irradiation, combining air circulation through light with light passage through air. 5. 5. By varying light distribution, the effective circulation between the occupied and the irradiated zone, below and above the seven-foot level in standard classrooms, was found to exceed four air changes a minute. The sanitary equivalent of 1,000 cubic feet of ventilation per minute per pupil was obtained by 6 foot watts of irradiation per pupil. This exceeds one-third of the maximum theoretical disinfection with uniformly distributed irradiation or infinite recirculation. 6. 6. Specification of sanitary ventilation by radiant disinfection is simplified by this formulation.