Dispersion of Microbes from Floors when Walking in Ventilated Rooms

Abstract

The redispersion factor of microbe-carrying particles, which is the ratio of the concentration of floor-derived microbes in room air to those on a floor surface, was determined, as was the percentage of floor-derived microbes in room air. These relationships were shown to vary according to conditions in the room. Equations were derived that allow these relationships to be calculated for a variety of room conditions, including air supply rates, levels of personnel activity, and the effect of gravitational deposition on microbe-carrying particles.The redispersion factor in ventilated rooms, such as cleanrooms and operating rooms, when the floor surface concentration was measured by nutrient agar contact dishes, was found to vary from about 1.5 × 10−4 to 7.4 × 10−6, and the percentage of floor-derived microbes in room air from about 0.004% to 10.5%. In a typical cleanroom, the redispersion factor is likely to be about 1.0 × 10−4, and the percentage of floor-derived microbes, 0.7. In a typical operating room, the redispersion factor is likely to be about 5.2 × 10−6 and the percentage of floor-derived microbes, 2.