Effects of Positive Pressure Ventilation System on Indoor Particulate Matter Concentrations in a Subtropical Climate

Air pollution negatively impacts human health, with pollutants such as PM 2.5 linked to increased mortality, respiratory infections, lung disease, heart disease, and stroke. Recent trends, such as increased building airtightness and changes in occupant behavior during the COVID‐19 pandemic, highlight the need for greater attention to indoor air quality (IAQ). Mechanical ventilation (MV) systems are commonly used to improve IAQ and occupant comfort, especially in airtight homes, yet their effectiveness in humid winter conditions remains underexplored. This study examined the impact of MV, specifically positive pressure ventilation (PPV) systems, on IAQ in eight single‐family homes in northern New Zealand. Data were collected over 12 weeks in winter, with 6 weeks of monitoring before and after PPV installation. Additionally, the study period overlapped with varying COVID‐19 lockdown levels, enabling an assessment of how increased occupancy influenced IAQ. The findings show that PPV system installation resulted in reductions over the winter period of 68% for particulate matter (PM) concentrations (both PM 2.5 and PM 10 ) and 9% in relative humidity (RH), with no significant changes in temperature. PM 2.5 concentrations increased by an average of 56% during the COVID lockdown, potentially resulting from increased occupancy levels.