Climate and occupancy based investigation of air pollutants in office spaces

Abstract

Abstract Indoor air quality (IAQ) has long been a matter of public concern as many people are spending a large portion of their time indoors. The concentration of some pollutant in offices and other work places can often be 2 to 5 times higher than typical outdoor concentrations. This study investigates the relationship between office space available per employee and outside weather condition with indoor pollutants level at 25 office locations of a large international architecture and design firm. Air pollutants measured in this study included carbon dioxide (CO2), particulate matter (PM2.5), and volatile organic compounds (VOCs). They have been monitored for a three-month period from December 1st, 2017 to February 28th, 2018 in 23 offices located in the U.S., one office in China, and one office in Dubai. The first phase of this study analyzed the hourly average levels of mentioned pollutants at these offices during working and non-working hours. Then those levels were correlated to the number of employees at all of the locations. The second phase observed the difference in CO2 level, as the most important indoor air pollutant, related to outside weather condition (temperature and humidity) at three locations in the U.S. The initial result of phase one proved the linear relationship between the number of employees and CO2 levels in office buildings. It concluded, that the low area per employee rate will cause the high CO2 concentrations. Moreover, a comparison between indoor CO2 level and outside weather conditions (temperature and humidity) in the second phase at three office shows that CO2 level are affected directly by outdoor conditions during working hours. Based on the building climate zone, when temperature and humidity are far from the comfort zone and mechanical ventilation system are operated, CO2 concentration could variously change during working hours.