Bio-contamination control in hospital environment by means of UV-C rays and HEPA filters

The contamination of air-handling units is a widespread phenomenon in buildings with air-conditioning (HVAC) systems and in hospitals. The germicide capacity of UV-C rays is known and into HVAC systems the UV-C lamps are generally located inside the air ducts. Aim of the paper is to evaluate the effectiveness of UV-C lamps for disinfection in case of direct irradiation of HEPA filter surface. An ad hoc experimental HVAC system, with HEPA filters and UV-C lamps, was built. During the period of activity, using first only HEPA filter and then also UV lamps, air samples were collected and total microbial and fungal count was performed; in addition, pressure drop through the filter was measured. Obtained results suggest that, in studied conditions, the radiation on filter surface reduces significantly microbial load and pressure drop through the filter, with respect to the case of not irradiated filter.