The concentration of particulate matter (both PM10 and PM2.5) are found to be 2-5 times higher than the permissible limits set by Central Pollution Control Board for ambient air quality, 100 μg/m3 for PM10 and 60 μg/m3 for PM2.5 (NAAQS, 2009) in India and 10-15 times higher than the WHO 24 hours average limits (50 μg/m3 and 25 μg/m3 PM10 and PM2.5 respectively) for all the monitored buildings (WHO,2016), say the findings of the Project MAQUID (Monitoring of Air Quality in Urban Indoors in Delhi).
The educational institutes (schools and colleges) top the list for high PM concentration. The Total Volatile Organic Compounds (TVOC) levels are also recorded high with highest in hospitals and restaurants due to rampant use of chemical cleaning agents, floor cleaners and cooking oils. Similarly, the CO2 levels were recorded high in hospitals, colleges, offices as well as in restaurants due to higher occupancy and inadequate ventilation. Though schools too have higher occupancy but all the selected schools are naturally ventilated so CO2 levels are within the permissible limits except one or 2 schools as defined by ASHRAE. The indoor/outdoor (I/O) ratios are calculated for PM10 and PM2.5 in the selected microenvironments. The schools fared the worst with the PM2.5 I/O ratios being reported more than one in all the selected six schools. I/O ratio more than one indicated the presence of a potential source indoors.
The highlighting factors from the findings of the study for research on IAQ research in India are:
- Concentrations of outdoor air pollutants penetrating to the indoor environments.
- Building materials with high TVOC compounds.
- Indoor agents, like paints, glues, polishing materials perfumes, spray propellants and cleaning agents.
- Building characteristics such as the air tightness and ventilation.
- Building occupancy and living space.
- Equipment used within the buildings (example, photocopiers, printers, heaters).
- The customs, habits and traditions of the residents.
The study was conducted on total 37 buildings across Delhi including the schools, colleges, hospitals, shopping malls, restaurants, offices and cinema halls (considered to be the priority indoor environments, where chances of exposure to indoor air pollutants are maximum) during the critical winter period for the city starting from 15th October 2019 – 30th January 2020.
24-hour monitoring was conducted in most of the selected buildings for indoor air pollutants, including PM10, PM2.5, TVOC along with comfort parameters (Temperature, Relative Humidity and CO2 concentrations) using Sensedge® air quality monitors from Kaiterra®, which is a medium cost sensor based monitor designed specifically for monitoring of Indoor air quality.
The physical characteristics, such as number of doors and windows, air purifiers, air conditioning systems, carpets, furniture, photocopiers and printers inside the building, running of diesel generator sets, distance of the buildings from the road sides with heavy traffic are also recorded during the study.
The baseline survey was conducted by Centre of Excellence for Research on Clean Air (CERCA), IIT Delhi; Society for Indoor Environment (SIE), and Kaiterra, an air quality instrument company.