The Research Triangle Institute (RTI) has developed a new fractional filtration efficiency laboratory test method for air cleaners used in general ventilation. The method provides a reliable and accurate means of measuring air cleaner fractional efficiencies over the particle diameter size range of 0.3 to 10 µm.

The need for a fractional efficiency test comes from several sources: (1) the growing concern with indoor air quality (IAQ); (2) the fact that filtration efficiency is often highly particlesize dependent for particles <10 µm diameter; (3) limitations of the current ASHRAE efficiency test (52.1-92 and its predecessor 52-76) which, by design, cannot differentiate between particle size; and (4) that respirable particles are generally classified as those <10-µm diameter.

Implementation of the new method will provide several benefits to the air cleaner community.