Ventilation rates in US office buildings from the EPA base study

The EPA BASE study involved indoor environmental measurements in 100 U.S. office buildings. This paper presents an analysis of the measured outdoor air ventilation rates, including comparisons with the requirements in ASHRAE Standard 62. The outdoor ventilation rates measured using duct traverses at the air handler intakes are higher than might be expected, with a mean value of about 55 L/s per person. However, these elevated values are not so unexpected given the low occupant density (mean of about 4 persons per 100 in 2) and the high outdoor air fractions (mean of about 35 %). Air change rates based on peak carbon dioxide concentrations in the space are lower than the volumetric values with a mean of about 20 L/s per person. Questions exist regarding the reliability of these peak CO2 values based on the validity of the assumptions on which the determinations are based.