Thisis a LibraryCirculatingCopy which may be borrowed for two weeks. and a geometric standard deviation of 2.0. Without air cleaner operation, the natural mass-averaged surface deposition rate of particles was observed to be 0

Data were collected in 70 detached houses built in 2011‐2017 in compliance with the mechanical ventilation requirements of California's building energy efficiency standards. Each home was monitored for a 1‐week period with windows closed and the central mechanical ventilation system operating. Pollutant measurements included time‐resolved fine particulate matter (PM2.5) indoors and outdoors and formaldehyde and carbon dioxide (CO2) indoors. Time‐integrated measurements were made for formaldehyde, NO2, and nitrogen oxides (NOX) indoors and outdoors. Operation of the cooktop, range hood, and other exhaust fans was continuously recorded during the monitoring period. Onetime diagnostic measurements included mechanical airflows and envelope and duct system air leakage. All homes met or were very close to meeting the ventilation requirements. On average, the dwelling unit ventilation fan moved 50% more airflow than the minimum requirement. Pollutant concentrations were similar to or lower than those reported in a 2006‐2007 study of California new homes built in 2002‐2005. Mean and median indoor concentrations were lower by 44% and 38% for formaldehyde and 44% and 54% for PM2.5. Ventilation fans were operating in only 26% of homes when first visited, and the control switches in many homes did not have informative labels as required by building standards.

Sampling and analytical methods for gas-and particulate-phase polycylic aromatic hydrocarbons (PAW in indoor air were evaluated in a controlled jield study. Using 12-h, 2S-m3 samples, gas-phase PAH were collected on XAD-4 resin and analyzed by GC-MS, and particulate-phase PAH were collected in filters and analyzed for by HPLC with fluorescence detection. Tests were conducted in homes and office buildings w i t h t active combustion sources and with gas stoves, wood stoves and cigarette smoking as controlled sources. Indoor concentrations, outdoor concentrations and air-exchange rates were simultaneozrs2y measured. The precistons of the concentrations were evaluated using collocated sample pairs collected indoors and outdoors. Net emission rates were calculated for the gas-phase PAH. Net emissions of these compounds were measured in buildings without active combustion sources. Environmtal tobacco smoke was dentijied as a signijiiant source of both gas-and particulate-phase PAH.

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