Evaluation of residential furnace filters.

Forced air furnaces are a common Canadian heating system. Traditionally, filters placed in the circulating air ductwork were designed to protect the furnace and fans . Over the last several years, there has been increased emphasis on improving the filtration efficiency with the goal of reducing occupant exposure to respirable particulate. This research project rotated several filters through six houses in southern Ontario during the heating season. Particulate levels were continuously monitored in the outside air, before and after the filter in the ducting system, and in the air in two rooms of each house. The results show that air passing through the filters was cleaned generally in accordance with rated filtration efficiency. The integrated breathing zone exposure, however, reflects both dust generation and dust removal mechanisms. Breathing zone exposure reductions were, therefore, not as significant as reductions seen in the ducting systems. A limited study of an in-room filter was also carried out and showed that such a filter can have significant effect on the breathing zone exposure in that room. A study of 15 additional houses with air cleaning by electrostatic precipitation looked at the levels of ozone found in these houses.