Experimentally evaluating the effectivness of an upper-room UVGI system

An experimental investigation was carried out to determine the effectiveness of an UltraViolet Germicidal Irradiation (UVGI) system for eradicating airborne pathogens in an indoor environment. Experimental and environmental conditions were varied and the resultant inactivated percentage of Staphylococcus aureus was measured. Results indicate that it is paramount to keep experimental parameters constant to achieve reliable and comparable results. In particular; the sampling plates used in the Andersen sampler must have a consistent depth of nutrient agar, and sufficient time (~ 40 mins) must be given for steady state conditions to be achieved prior to the commencement of air sampling. Furthermore a change in environmental conditions such as ventilation regime and ventilation rate, were found to significantly influence the determination of the effectiveness of an upper-room UVGI system; with a ventilation regime of in low, out high resulting in an average of 16 % higher microorganism inactivation than a regime of in high, out low. The environmental conditions for which the device was deemed most effective, i.e. which resulted in the highest percentage of airborne microorganisms inactivated (96.0 ± 3.2 %) were: for a ventilation rate of 3 air changes per hour (ACH) and ventilation regime of in low, out high.