es6b03069_si_001.pdf (427.9 kB)
Ozone, Electrostatic Precipitators, and Particle Number Concentrations: Correlations Observed in a Real Office during Working Hours
journal contribution
posted on 2016-08-29, 00:00 authored by Jianbang Xiang, Charles J. Weschler, Jinhan Mo, Drew Day, Junfeng Zhang, Yinping ZhangThis
study investigates the impacts of outdoor and indoor ozone
concentrations, ESP operation and occupancy on particle number concentrations
within a modern office in Changsha, China. The office’s one-pass
air handling system contains a mini-bag filter (MERV 12) followed
by an electrostatic precipitator (ESP) and high efficiency particulate
air (HEPA) filter. Over a five-week period the system was operated
either without the ESP (Stage 1, first–third week) or with
the ESP (Stage 2, fourth and fifth week). Ozone and particle number
concentrations were measured on working days. During both stages,
indoor ozone and particle number concentrations tracked the outdoor
ozone concentration. When operating, the ESP produced approximately
29 mg h–1 of ozone, increasing supply air ozone
by 15 ppb and steady-state indoor ozone by about 3 ppb. Occupancy
tended to decrease indoor ozone and increase particle levels. During
occupancy, indoor particle levels were low (∼2600 particle/cm3) when the supply air ozone level was less than 18 ppb. Above
this threshold, the supply air ozone concentration and indoor particle
number concentration were linearly related, and ESP operation increased
the average indoor particle level by about 22 000 particles/cm3. The implications for worker exposure to both ozone and particles
are discussed.