Indoor air quality in new and renovated low‐income apartments with mechanical ventilation and natural gas cooking in California

This study presents pollutant concentrations and performance data for
code-required mechanical ventilation equipment in 23 low-income apartments
at 4 properties constructed or renovated 2013-2017. All apartments had
natural gas cooking burners. Occupants pledged to not use windows for
ventilation during the study but several did. Measured airflows of range
hoods and bathroom exhaust fans were lower than product specifications.
Only eight apartments operationally met all ventilation code requirements.
Pollutants measured over one week in each apartment included time-resolved
fine particulate matter (PM2.5), nitrogen dioxide (NO2), formaldehyde and
carbon dioxide (CO2) and time-integrated formaldehyde, NO2 and nitrogen
oxides (NOX). Compared to a recent study of California houses
with code-compliant ventilation, apartments were smaller, had fewer
occupants, higher densities, and higher mechanical ventilation rates. Mean
PM2.5, formaldehyde, NO2, and CO2 were 7.7 µg/m3, 14.1 ppb, 18.8 ppb, and
741 ppm in apartments; these are 4% lower, 25% lower, 165% higher, and 18%
higher compared to houses with similar cooking frequency. Four apartments
had weekly PM2.5 above the California annual outdoor standard of 12 µg/m3
and also discrete days above the World Health Organization 24-h guideline
of 25 µg/m3. Two apartments had weekly NO2 above the California annual
outdoor standard of 30 ppb.