Indoor–outdoor concentrations of particulate matter in nine microenvironments of a mix-use commercial building in megacity Delhi

Three naturally and six mechanically ventilated microenvironments (MEs) of a mixed use commercial building in Delhi are used to study indoor–outdoor (I/O) relationships of particulate matter ≤10μm (PM10), ≤2.5μm (PM2.5) and ≤1μm (PM1). Effect of environmental and occupancy parameters on the concentrations of PM during working and non–working hours (i.e. activity and non-activity periods, respectively) are also investigated. Average outdoor concentration of PM10 and PM2.5 were found to exceed the 24 hour averaged national standard values, showing a polluted environment surrounding the studied building. During the working hours, indoor PM10 concentration was found 6–10 times, both PM2.5 and PM1 were 1.5–2 times, higher than the non–working hours in the selected MEs. The variations of indoor concentrations were highest (17.1–601.2 μg/m) for PM10 compared with PM2.5 (16.9–102.6 μg/m ) and PM1.0 (10.6–63.6 μg/m ). The I/O for PM10, PM2.5 and PM1.0 varied from 0.37–3.1, 0.2–3.2 and 0.17–2.9, respectively. The results suggest highest I/O for PM10, PM2.5 and PM1 as 3.1, 2.15 and 1.76, respectively, in all the three natural ventilated MEs (canteen, kitchen, reception). Irrespective of PM types, the average I/O was <1 for mechanically ventilated MEs compared with >1 for naturally ventilated MEs. As opposed to PM1, better correlation (r >0.6) was noted between indoor PM10, PM2.5 and CO2 concentrations in most of the airtight MEs.