Exploring nanoparticle emissions and size distributions during incense burning and filtration in an indoor space

Indoor air pollution is a critical health issue. We studied particle emissions, concentration changes and size distribution mechanisms using an indoor space with air quality monitors, incense stick burning, and ventilation. Temporal changes in the concentrations of particles with sizes of 10 nm to 10 µm were monitored. Our findings show that particles affecting particle number concentration (PNC) were mainly in the Aitken mode (50–100 nm) and accumulation mode I (100–200 nm). Particle surface area concentration (PAC) was primarily in the 100–300 nm range, while particle volume concentration (PVC) was in the 100–200 nm and 300–1000 nm ranges. After extinguishing the incense sticks, ventilation was initiated. The ventilation period was split into FAO_1–3 (i.e., the first 3 min, 1–3 min of ventilation system operation) and FAO_4–15 (i.e., the last 12 min, 4–15 min of ventilation system operation). During FAO_1–3, particle concentrations increased by 18.3 to 21.5%. This rise was due to the initial activation of the ventilation system, dispersing settled particles (mostly ≥ 41.2 nm) into the air. The FAO_4–15/FAO_1–3 ratio for 12.3−2489.3 nm particles was always < 1, indicating that as the ventilation continued, it effectively removed particles of < 2.5 μm. After subsequent ventilation of 15-min operation, total PNC, PAC, and PVC were 70.3%, 70.0%, and 67.8% lower than during FAO_1–3 and the particle number mode diameter was 106.0 nm, with geometric standard deviations of 1.50 and 1.51 (left and right), indicating that the ventilation system was successful in removing smoke particles of all sizes simultaneously and evenly and achieved an approximate total removal efficiency of 70%, effectively filtering particles and reducing indoor air pollution.

Graphical abstract