Influence of Ventilation on Formation and Growth of 1–20 nm Particles via Ozone–Human Chemistry

Abstract

Ozone reaction with human surfaces is an important source of ultrafine particles indoors. However, 1−20 nm particles generated from ozone−human chemistry, which mark the first step of particle formation and growth, remain understudied. Ventilation and indoor air movement could have important implications for these processes. Therefore, in a controlled-climate chamber, we measured ultrafine particles initiated from ozone−human chemistry and their dependence on the air change rate (ACR, 0.5, 1.5, and 3 h −1 ) and operation of mixing fans (on and off). Concurrently, we measured volatile organic compounds (VOCs) and explored the correlation between particles and gas-phase products. At 25−30 ppb ozone levels, humans generated 0.2−7.7 × 10 12 of 1−3 nm, 0−7.2 × 10 12 of 3−10 nm, and 0−1.3 × 10 12 of 10−20 nm particles per person per hour depending on the ACR and mixing fan operation. Size-dependent particle growth and formation rates increased with higher ACR. The operation of mixing fans suppressed the particle formation and growth, owing to enhanced surface deposition of the newly formed particles and their precursors. Correlation analyses revealed complex interactions between the particles and VOCs initiated by ozone−human chemistry. The results imply that ventilation and indoor air movement may have a more significant influence on particle dynamics and fate relative to indoor chemistry.

Ozone generation and chemistry from 222 nm germicidal ultraviolet light in a fragrant restroom

“…Recently, fan mixing prevented the growth of newly-formed particles <3 nm to larger sizes in a chamber where occupants were exposed to O 3 . 41 Continued research into the influence of air mixing on particle formation dynamics from O 3 reactions is warranted.…”

Nanocluster Aerosols from Ozone–Human Chemistry Are Dominated by Squalene–Ozone Reactions

“…Our recent investigation of the impact of air change rates on NCA formation via ozone–human chemistry indicated a positive correlation between the NCA formation rate and the ozone removal rate, which provided insights into this study regarding the dependence of NCA generation on ozone level. 19 …”

“…Our previous studies were the first to report NCA formation via ozone–human chemistry and ozone chemistry on worn clothing . Moreover, our recent study showed that the NCAs formed during ozone–human chemistry can grow into ultrafine particles ranging from 10 to 55 nm, depending on ventilation and indoor air movement . Nevertheless, the driving mechanisms of ozone–human chemistry generating NCAs remain unexplored.…”

“… 18 Moreover, our recent study showed that the NCAs formed during ozone–human chemistry can grow into ultrafine particles ranging from 10 to 55 nm, depending on ventilation and indoor air movement. 19 Nevertheless, the driving mechanisms of ozone–human chemistry generating NCAs remain unexplored. A fundamental question yet to be addressed is which constituent of human skin lipids plays the most significant role in NCA formation in the presence of ozone.…”