When Fresh Air Isn’t Clean: Indoor Air Quality Response to Bushfire Smoke in a Naturally Ventilated Melbourne Dwelling

Bushfire smoke events pose increasing risks to indoor air quality (IAQ), particularly in naturally ventilated residential buildings. This study investigates the short-term response of indoor air quality to a bushfire smoke episode in a Melbourne dwelling using high-resolution field measurements. Indoor parameters (CO₂, PM₂.₅, PM₁₀, temperature, and relative humidity) were monitored alongside outdoor conditions, with occupancy and window operation recorded. A significant increase in indoor particulate matter was observed during a documented bushfire event, while CO₂ levels remained stable, indicating pollutant ingress under open-window conditions. The findings highlight the trade-off between ventilation and exposure during extreme events and demonstrate the importance of occupant behaviour in shaping IAQ outcomes. This study provides real-world evidence to inform IAQ management strategies in residential buildings under bushfire conditions.