Particulate matter in residential buildings in New Zealand: Part II. The impact of building airtightness, mechanical ventilation using simulated occupancy

Many occupant activities can adversely affect indoor air quality which has been shown to be detrimental to human health. This research eliminated some of the variability of previous measured levels of indoor particulate matter (PM) by removing all human activity and providing baseline data on the contribution occurring from home furnishings. Further objectives included investigating the effects of airtightness and mechanical ventilation on internal PM concentrations with controlled simulated occupancy. With natural ventilation, PM concentrations were 15% greater in bedroom of the less airtight (Control) house than that of the (Test house), post-furnishing which indicates that there is a considerable amount of natural variation which may not be solely due to occupant activities. Simulated occupancy dramatically increased the concentration of PM found in both houses by just under 5-fold. With simulated occupancy, the majority of the PM was present as fine particles (<= PM1) for both houses (93-94%), whereas without simulated occupancy, the proportion of fine particles was lower (88-89%). After furnishing and without the use of mechanical ventilation, PM10 concentrations exceeded the WHO Guidelines for PM10 of 50 mu g m(-3) for 56% of the testing duration for the Control bedroom and 35% for the Test bedroom. The use of mechanical ventilation reduced the mean internal PM concentrations by approximately 90% for all PM sizes in both study bedrooms which highlights the importance of use and maintenance of effective ventilation systems especially after furnishing activities.