Airborne Bacteria Control Under Chamber and Test-Home Conditions

The research reported in this paper investigates the ability of a portable UV-based control device $(\mathrm{size}=21\mathrm{in}\text{.}\times 12\mathrm{in}\text{.}\times 12\mathrm{in}\text{.})$ to reduce airborne indoor bacteria levels to at or below outdoor ambient levels. Under controlled conditions, laboratory scale chamber $(\mathrm{size}=48\mathrm{in}\text{.}\times 36\mathrm{in}\text{.}\times 48\mathrm{in}\text{.})$ experiments and field scale residence experiments were conducted using the UV control device. Pure cultures of Staphylococcus aureus were grown in culture media and atomized into bioaerosols in the laboratory chamber. The airborne levels of the bacteria were sampled using a six-stage Andersen sampler containing selective culture media plates, and the levels were counted as number of colony forming units per cubic meter of air. The UV control device reduced the atomizer-generated laboratory chamber Staphylococcus aureus levels from a range of 5,000–15,000 cfu/m³ to below 120 cfu/m³ within a 2 h period. Continuous operation of the UV control device in the bedroom and bathroom of a single-resident apartment reduced the Staphylococcus aureus counts from a range of 200–1,300 to less than 200 cfu/m³. The unit cost of the prototype UV control device is estimated at $120, and the operating cost is estimated at $0.74/day.