‘Absolute’ or HEPA (High Efficiency Particulate Air) filters are designed the most demanding of operating conditions, principally where the rate of airflow is high and where the level of cleanliness is critical. Common uses include operating theatres, power stations, clean rooms, pharmaceutical industries, chemical plants, computer rooms and electronics. Due to the critical nature of such applications, each individual finished filter is subjected to a quality test. The filtration medium is a water-proof, fire –resistant glass fibre paper available in efficiencies from 98-99.997% (0.003) set in a cold-sure resin seal. Recommended for use with pre-filters for extended life.