Comparison of Indoor Air Quality for Air-Conditioned and Naturally Ventilated Office Spaces in Urban Area

Indoor air quality (IAQ) is affected by indoor pollution sources that release gases or particles into the air and depending on ventilation conditions, outdoor ambient air quality can also be contributing factor. Inadequate ventilation by limiting inflow-outflow of pollutants, proximity to field or busy road can increase indoor pollutant levels. For this study, two offices, one with natural ventilation and other with central AC system, within residential campus of IIT Kanpur were selected. Air quality in offices with varying ventilation conditions was monitored simultaneously indoor and outdoor. The aim was to compare the data for the two locations and elicit influence of ventilation conditions on indoor pollutant levels. Size segregated mass concentration of ambient aerosols and particle number concentration (PNC) were determined for indoor using cascade impactor, MOUDI and OPC, respectively. Outdoor coarse particle concentration (PM10) was determined using HVS sampler. The PM concentration was found to be highest in naturally ventilated office. As per the recently released ISHRAE standards for indoor environment (ISHRAE Standard-10001:2016), minimum acceptable limits for Class C are PM10 < 100 mu g/m(3) and PM2.5 < 25 mu g/m(3). Levels of particles recorded in these office spaces were 4-6 times higher than ISHRAE acceptable limits for PM2.5 and PM10, respectively. Particle number concentration (PNC) was also higher in naturally ventilated office space as concentration was more than 400,000 particles/cm(3) (<1 mu m) as compared to airconditioned office space (160,000 particles/cm(3)). The I/O ratio for PM10 was found to be 0.64 and 2.93 for Office 1 and Office 2, respectively.