The effects of improved residential filtration on particulate exposure.

Forced air furnaces are a common Canadian heating system. Traditionally, filters placed in thecirculating air ductwork were designed to protect the furnace and fans. Over the last severalyears, there has been increased emphasis on improving the filtration efficiency with the goal ofreducing occupant exposure to respirable particulate. The current research project rotatedseveral filters through six houses in southern Ontario during the heating season. Particulatelevels were continuously monitored in the outside air, before and after the filter in the ductingsystem, and in the air in two rooms of each house. The results show that air passing throughthe filters was cleaned generally in accordance with rated filtration efficiency. The integratedbreathing zone exposure, however, reflects both dust generation and dust removalmechanisms. Breathing zone exposure reductions were therefore not as significant asreductions seen in the ducting systems. A study of 15 additional houses with air cleaning byelectrostatic precipitation looked at the levels of ozone found in these houses.