Particle size characterization and emission rates during indoor activities in a house

Abstract

Characterization and emission rates of indoor aerosols have been of great interest. However, few studies have presented quantitative determinations of aerosol particle emissions during indoor activities. In the current study we presented and investigated the physical characteristics and size-fractionated emission rates of indoor aerosol particles during different activities in a house (naturally ventilated) located in Prague, Czech Republic. We utilized a multi-compartment and size-resolved indoor aerosol model (MC-SIAM) to investigate the indoor-to-outdoor relationship of aerosol particles and also to estimate their emission rates. When the windows and the main door were closed for several hours and there were minor indoor activities that did not produce significant amounts of aerosol particles, the particle number concentration showed similar levels at different indoor locations. As expected, the natural ventilation did not provide a controlled indoor-to-outdoor relationship of aerosol particles. As previous studies have emphasized, cooking and tobacco smoking activities are major sources indoors; the total particle number concentration was, respectively, as high as 1.8×10 5 and 3.6×10 4 cm −3 with emission rates around 380 and 36 cm −3 s −1. During intensive cooking activities the outdoor aerosol particle concentrations were also affected even though windows were closed. It seems that a simple model is not able to describe the fate of indoor aerosols within a multi-compartment construction; instead, a numerical and dynamic model with a multi-compartment approach is needed. Based on the indoor aerosol model simulations, the deposition rate was comparable to previous studies with friction velocity between 10–30 cm s −1 and surface area to volume ratio around 2.9–3.1 m −1. The penetration factor was equivalent to G3 filter standards and the ventilation rate varied between 0.6–1.2 h −1. Based on the emission rate analysis, aerosol particles produced during tobacco smoking and incense stick burning remain airborne for a longer time than cooking particles. It seems that aerosol particles emitted during tobacco smoking and incense stick burning undergo different processes; therefore, there is a need for a combined physical–chemical indoor aerosol model to better describe the evolution of indoor aerosol particles due to different activities.