Indoor air quality can be worse than outdoors, study by Ahmedabad University finds

Led by Professor Aditya Vaishya at Ahmedabad University, the study installed air quality sensors across three types of spaces in Ahmedabad over a six-month period: an outdoor location, a standard indoor space like a classroom or office, and an indoor space with an active pollution source like a burning stove. In total, seven to eight spaces were monitored for PM levels, ozone, temperature, and relative humidity.

“The findings challenged the commonly held belief that indoor air is safer. In fact, PM concentrations indoors were higher than outdoor levels for more than 50 percent of the time, regardless of whether a pollution source was present. Many of these pollutants are emitted by everyday items and processes such as perfumes, disinfectants, room sprays, and even routine cooking,” said Prof Vaishya, assistant professor at the School of Arts and Sciences, Ahmedabad University. He leads the Air and Water Vertical at The Climate Institute and heads the Air and Climate Research Laboratory.

Prof Vaishya further said that in confined spaces, pollutants tend to accumulate and linger, increasing exposure. “This indoor pollution poses a significant risk, especially for vulnerable populations such as children, women, and domestic workers, who tend to spend more time indoors,” he said.

Research scholar Yash Dahima, part of the study team, added, “Sensitisation and awareness towards indoor air quality is more important as there is limited control over outdoor air quality whereas we can have control over sources of pollutants indoors. For instance, adding cross ventilation or windows helps expel cooking toxins. There is a pressing need for the construction and housing sector to build houses with better ventilation systems. Residents can also install exhaust fans in kitchens, limit the use of synthetic air fresheners and aerosols, and add air-purifying indoor plants, which can also make a meaningful difference.”

The research also highlights social equity concerns. Domestic workers often spend long hours in multiple homes, exposed to poor indoor air quality without having any say in their work environment. The Air and Climate Research Laboratory plans to explore these dimensions of environmental and social justice in future research.

While this phase of the study focused on particulate matter, the team now plans to monitor gases like sulphur dioxide, nitrogen dioxide, and ozone, which are linked to various health risks.

“With ongoing research at the lab, we are in talks with a not-for-profit organisation to expand the study’s reach. The portable IoT-based low-cost air quality monitoring devices developed as part of the campaign will be installed at various types of homes – kutcha and dense clusters without ventilation or windows – identified during our field survey to assess the kind of gases building up,” said Prof Vaishya.

“Indoor air pollution is invisible but highly dangerous, and addressing it requires a combination of scientific understanding, social awareness, and policy action. In addition to studies, we are also in final talks with other non-profit organisations whose volunteers will sensitise people towards indoor air pollution,” he said.