Filtration efficiency of woven metal fiber filter for aerosol generated by plasma torch metal cutting

An air conditioning unit with the HEPA filter should be operated in the dismantling workspace of nuclear power plants because of massive release of radioactive aerosols due to radioactively contaminated metal cutting. The HEPA filter has a good performance against nano- or micro-sized aerosols but is frequently replaced to maintain the filtration efficiency in the workplace. A woven metal fiber mesh filter (Type I) and a woven metal and glassy fiber mesh filter (Type II) have been developed as prefilter to increase the lifespan of HEPA filter. The accredited certification according to ASHRAE Standard 52.2 methodology showed that Type I and Type II filters were certified the MERV rating 7 and 10 respectively. The filtration efficiency of each filter has been evaluated under the metal cutting environment with plasma torch. Aerosols at upstream and downstream sides of the filter were simultaneously measured in the ranges of 6 nm to 10 & mu;m with high-resolution impactor, and filtration efficiency of each filter was calculated with the measured size distribution of aerosols. Experimental results showed that Type II filter had higher efficiency in the ranges of 0.3 to 10 & mu;m than Type I filter and met the MERV rating 10. Both filters showed the minimum filtration efficiency of about 60-70% at 0.3 & mu;m, which is a theoretical MPPS of HEPA filter. Both filters are adequate for pre-filter of the HEPA filter and could contribute to mitigation of the particle removal load on the HEPA filter and the life extension of the HEPA filter.Copyright & COPY; 2023 American Association for Aerosol Research