Development of air purification system in air-conditioned spaces

Indoor air purification becomes a popular topic since the outbreak of Severe Acute Respiratory Syndromes (SARS) in 2003. Bacteria and viral contamination in indoor air has become a serious concern in healthcare facilities. In addition, there was a market boom in air purification products during the outbreak. This paper reviews major technologies available for bacteria removal, including ultraviolet (UV) light, photo-catalytic oxidation, HEPA filters; and describes the testing results of an air purification system in a University clinic. The system was installed with UV lamps and titanium dioxide honeycomb section for photo-catalytic oxidation. Total bacteria count was measured to test the effectiveness of the system. Without the use of purifier, the bacteria count could reach 500-600 cfu/m(3) when there are 18 persons or more in the clinic waiting area. The air purifier can reduce the bacteria count to 400-450 cfu/m(3) under similar occupancy condition. In addition, two bacteria decay profiles were measured after clinic service hour. The one with the use of air purifier could achieve a decay rate of 4.72 hr(-1), comparing with the natural decay rate of 0.95 hr(-1).