Performance qualification of a HEPA filter at high temperature

The authors propose a method for the control of the filtering characteristics of high-efficiency particulate air (HEPA) filters set up in the sterilization tunnels at a temperature of 300°C and beyond, corresponding to the operating conditions. In the present work the HEPA filter efficiency has been evaluated both with oily aerosol of bis(2-ethylhexyl)sebacate and with pre-calibrated barium sulphate particles. The former was used at room temperature, while for the latter also the working temperature of the sterilization tunnel was employed. Furthermore, attention was given to the airborne particulate cleanliness classes of the filtering characteristics of HEPA filters at high temperature. The results obtained in the present investigation confirm the practicability of our method to evaluate the filtering characteristics at the working conditions, primarily during the performance qualification steps.