Naveen Puttaswamy This email address is being protected from spambots. You need JavaScript enabled to view it.1, V. Sreekanth2, Ajay Pillarisetti3, Adithi R. Upadhya4, Sudhakar Saidam1, Balachandar Veerappan1, Krishnendu Mukhopadhyay1, Sankar Sambandam1, Ronak Sutaria5, Kalpana Balakrishnan1 

1 Department of Environmental Health Engineering, Faculty of Public Health, Sri Ramachandra Institute of Higher Education and Research, Chennai 600 116, India
2 Center for Study of Science, Technology and Policy, Bengaluru 560 094, India
3 Gangarosa Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, USA
4 ILK Labs, Bengaluru, India
5 Respirer Living Sciences Private Limited, Pune, India

Received: July 13, 2021
Revised: November 6, 2021
Accepted: December 1, 2021

 Copyright The Author's institutions. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited. 

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Puttaswamy, N., Sreekanth, V., Pillarisetti, A., Upadhya, A.R., Saidam, S., Veerappan, B., Mukhopadhyay, K., Sambandam, S., Sutaria, R., Balakrishnan, K. (2022). Indoor and Ambient Air Pollution in Chennai, India during COVID-19 Lockdown: An Affordable Sensors Study. Aerosol Air Qual. Res. 22, 210170.


  • Simultaneous monitoring of indoor PM2.5 and PM10 in Chennai during COVID-19 lockdown.
  • Data from locally calibrated portable and affordable real-time monitors was showcased.
  • Observed significant reduction (as high as 90%) in indoor PM during lockdown.
  • The indoor to outdoor ratios in PM2.5 marginally increased during lockdown.


The Tamil Nadu Air Pollution and Health Effects study (TAPHE-2) aims to evaluate the relationship between air pollution and birth outcome in a rural-urban cohort of 300 pregnant women. Due to COVID-19 related lockdowns, some TAPHE-2 activities were delayed; however, continuous indoor and outdoor air quality data were collected in and around Chennai, India. We report here the impact of graded COVID-19 lockdown on indoor particulate matter (PM2.5 and PM10) levels based on calibrated data from affordable real-time PM sensors called atmos™ and ambient PM levels from publicly available regulatory monitors. The study period was between 11 March and 30 June 2020 (i.e., 100 days of continuous monitoring), which coincided with four phases of a nationwide graded lockdown. Field calibration coefficients for the atmos PM were derived by collocating them with reference-grade PM monitors. The normalized root mean square error (NRMSE) of the atmos hourly PM2.5 (PM10) improved from 41% to 15% (33% to 18%) after applying the field calibration coefficients. Lockdowns resulted in significant reductions in indoor and ambient PM levels, with the highest reduction observed during lockdown phase 2 (L2) and phase 3 (L3). Reductions as high as 70%, 91%, and 62% were observed in ambient PM2.5, indoor PM2.5, and indoor PM10 relative to pre-lockdown levels (PL), respectively. The indoor PM2.5/PM10 ratio decreased during the lockdown, suggesting a decline in the fine mode dominance in PM10. The indoor-to-outdoor (I/O) ratios in PM2.5 marginally increased during L1, L2, and L3 phases compared to that of PL levels, suggesting an uneven reduction in indoor and ambient PM2.5 levels during the lockdown.

Keywords: Optical scattering, PM2.5, PM10, Beta Attenuation Monitor, Indoor to outdoor ratio

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