<p>Last winter, a family in Delhi spent two days in the hospital after their young daughter collapsed while preparing breakfast. The culprit was not a visible gas leak or unsafe water. Instead, it was the invisible buildup of fine particles and stale air in their apartment—a reality faced by millions across India's cities and villages, often without warning or diagnosis. </p><p>Every winter, images of smog-covered skylines return to India’s media pages, accompanied by familiar warnings about unhealthy outdoor air. This imagery tells only one side of the story—the outdoors. While a segment of the population spends significant time outside, most Indians spend an average of 19 to 21 hours a day indoors. There is no data to suggest that the indoors is healthier; in fact, while we may feel psychologically more secure inside buildings, indoor air quality remains poor. The symbiotic relationship between indoors and outdoors is working against us when it comes to air quality. Polluted outdoor air degrades indoor quality, as most Indian buildings interact seamlessly with the exterior, and we also generate additional pollutants indoors.</p><p>Improved indoor air quality (IAQ) is emerging as a key determinant of public health. It cannot be achieved solely through technology, building design, or the management of urban settings; rather, achieving desired IAQ requires organised societal efforts. Because it demands integration across environmental, social, and economic domains, IAQ has become a critical factor in modern public health. While air quality and particulate pollution outdoors continue to dominate public discourse, the next frontier of public health will lie within the walls of our buildings.</p><h3>What defines healthy indoor air</h3><p>Two indicators offer a clear window into the health of indoor environments: fine particulate matter (PM2.5) and carbon dioxide (CO₂). To put PM2.5 in perspective, these particles are about 30 times smaller than the width of a human hair, so tiny that thousands could fit across a single strand. PM2.5, microscopic particles small enough to enter the bloodstream, infiltrates indoor spaces from outdoor pollution but is also generated indoors through cooking, dust resuspension, building materials, and combustion sources. Carbon dioxide, meanwhile, is not harmful at typical indoor levels but acts as a critical proxy for ventilation. When CO₂ levels rise, they signal inadequate fresh air exchange and the buildup of pollutants, pathogens, and stale air.</p><p>Research from the Harvard T.H. Chan School of Public Health’s Healthy Buildings program has shown that improved ventilation and filtration can significantly reduce indoor particulate exposure. More strikingly, their work demonstrates that elevated CO₂ and particulate levels impair cognitive function, slow response times, and reduce decision-making performance. In one study, cognitive scores dropped by up to 15% when CO₂ and particulate levels were elevated, compared to well-ventilated conditions. In classrooms, this can influence learning outcomes. In workplaces, it affects productivity and concentration. In homes, it shapes sleep quality, recovery, and overall well-being.</p><p>Indoor air quality is therefore not merely a respiratory health issue. It affects how we think, learn, and perform.</p><h3>India’s built environment challenge</h3><p>India’s built environment presents a complex IAQ challenge. For example, typical indoor PM2.5 concentrations in urban apartments can range from 60–90 µg/m³ on high-pollution days, as outdoor air seeps in through poorly sealed structures. In contrast, few kitchens using biomass fuels in rural areas may experience indoor PM2.5 levels that soar well above 150 µg/m³ during cooking, driven by solid-fuel combustion and dust. High-density living in cities reduces effective ventilation, and the increasing adoption of mechanical systems prioritise thermal comfort and energy consumption over fresh air exchange. This led to a situation that buildings designed to conserve energy without keeping the IAQ as focus can trap pollutants when ventilation is poorly designed. Ironically, buildings rely on energy-inefficient mechanical systems even when outdoor temperatures are comfortable for 25% to 30% of the year. Poor air quality prevents us from using this natural ventilation, forcing a continued dependence on energy-intensive mechanical systems.</p><p>While Indian national policies and actions prescribe the measurements and monitoring at multiple outdoor spatial levels, IAQ measurement and awareness is yet to break the ground. This invisibility has economic consequences as well as health implications. Preliminary research suggests that improving indoor air quality in workplaces and schools can boost cognitive function and productivity, potentially translating into significant gains in GDP over time. For example, a 2020 pilot study in Bengaluru offices reported that installing air filtration systems reduced PM2.5 concentrations and was associated with measurable improvements in employee task performance and reduced absenteeism (Ramachandran et al., 2020). For a country like India, even a 1% boost in workforce productivity through healthier indoor environments could amount to crore of rupees in additional economic output each year. Quantifying and publicising these benefits may help accelerate the adoption of the best practices. </p><p>Market signals suggest that awareness is beginning to shift. In several polluted urban centres, developers are now marketing “low-AQI homes” equipped with filtration systems and controlled ventilation as premium offerings. This reflects a growing recognition that health is becoming a defining metric of built environments. Ensuring access to clean indoor air must be viewed as a fundamental public health necessity rather than an optional luxury. </p><h3>Designing buildings that breathe</h3><p>The first step toward healthier indoor environments is measurement. Cities monitor outdoor air quality in real time; buildings must begin to do the same. Advances in sensor technology now make it possible to continuously track PM2.5, CO₂, temperature, humidity, and ventilation performance. Real-time data allows facility managers to adjust ventilation rates, improve filtration, and respond to pollution spikes. Over time, such monitoring can create benchmarks for healthy buildings, much as water quality standards transformed public health in the twentieth century.</p><p>Improving indoor air does not require futuristic technology. Proven solutions exist: adequate ventilation, high-efficiency filtration, low-emission building materials, source control for indoor pollution, and smart HVAC systems that balance energy efficiency with fresh air exchange. International research suggests that CO₂ levels below 800–1000 ppm typically indicate well-ventilated spaces, while higher levels signal inadequate airflow and potential pollutant buildup.</p><p>In India, where climate extremes and energy constraints shape building operations, the challenge is to balance thermal comfort, energy use, and ventilation. While smart building design—such as mixed-mode ventilation, demand-controlled airflow, and occupancy-aware systems—offers the potential to improve air quality alongside energy efficiency, the practical implementation of these technologies can face significant hurdles. These challenges may include high upfront costs, , complex maintenance, and adaptation of existing infrastructure. While high utility costs are a concern, research shows that smart ventilation systems save money by adjusting airflow based on how many people are in the room. </p><h3>What building-level data is already showing</h3><p>The intersection of indoor air quality, climate adaption, and economic productivity is particularly important for India. Healthier indoor environments can reduce disease burden and healthcare costs, improve cognitive performance and workplace efficiency, and enhance learning outcomes in schools. </p><p>There are early examples demonstrating what this transition can look like. In several Indian cities, building-level monitoring initiatives have begun to track indoor particulate levels and ventilation performance in offices, transport hubs, and public facilities. Real-time environmental monitoring work has shown how building-level PM2.5 and CO₂ tracking can reveal pollution patterns invisible to occupants — from particulate spikes during peak traffic infiltration to elevated CO₂ levels in meeting rooms with poor ventilation. In a study commissioned by Cummins India Foundation and CSIR-NCL based Venture Center Pune – 10 schools in Delhi and Mumbai were found to have over 130 to 230 ug/m3 as average PM2.5 over a month-long evaluation during winter 2026. In one commercial building pilot, ventilation adjustments guided by real-time CO₂ data improved air exchange rates while optimising energy use, highlighting how data-driven management can support both health and efficiency.</p><p>Such interventions remain the exception rather than the norm. But they illustrate a critical point: indoor air quality is measurable, manageable, and improvable.</p><h3>The next frontier of clean air actions</h3><p>Globally, the concept of “healthy buildings” is gaining traction, driven by lessons from the pandemic, workplace productivity research, and rising awareness of environmental health. International climate and health frameworks increasingly recognise the importance of indoor environments in shaping resilience and wellbeing. India, with its scale of urbanisation and infrastructure growth, has an opportunity to integrate IAQ into the future of building design and public health actions.</p><p>The evolution of air quality management will not stop at citywide dashboards. It will extend to the spaces where we spend our lives: homes, classrooms, workplaces, transit systems, and healthcare facilities. Just as clean drinking water became a baseline expectation through actions by government, engineering, and monitoring, clean indoor air must become a design standard rather than a premium feature.</p><p>Because the future of healthy living will not be defined only by the air outside our windows, but by the air inside our buildings.</p><h3> <strong>Author Bio</strong></h3><p>Ronak Sutaria is Founder and CEO of Respirer Living Sciences, an environmental intelligence organisation working at the intersection of air quality, climate sciences, and urban policy.</p><p>Rajan Rawal is a Professor at CEPT University and a senior advisor at the Center for Advanced Research in Building Science and Energy (CARBSE), CEPT Research and Development Foundation (CRDF).</p>
<p>Last winter, a family in Delhi spent two days in the hospital after their young daughter collapsed while preparing breakfast. The culprit was not a visible gas leak or unsafe water. Instead, it was the invisible buildup of fine particles and stale air in their apartment—a reality faced by millions across India's cities and villages, often without warning or diagnosis. </p><p>Every winter, images of smog-covered skylines return to India’s media pages, accompanied by familiar warnings about unhealthy outdoor air. This imagery tells only one side of the story—the outdoors. While a segment of the population spends significant time outside, most Indians spend an average of 19 to 21 hours a day indoors. There is no data to suggest that the indoors is healthier; in fact, while we may feel psychologically more secure inside buildings, indoor air quality remains poor. The symbiotic relationship between indoors and outdoors is working against us when it comes to air quality. Polluted outdoor air degrades indoor quality, as most Indian buildings interact seamlessly with the exterior, and we also generate additional pollutants indoors.</p><p>Improved indoor air quality (IAQ) is emerging as a key determinant of public health. It cannot be achieved solely through technology, building design, or the management of urban settings; rather, achieving desired IAQ requires organised societal efforts. Because it demands integration across environmental, social, and economic domains, IAQ has become a critical factor in modern public health. While air quality and particulate pollution outdoors continue to dominate public discourse, the next frontier of public health will lie within the walls of our buildings.</p><h3>What defines healthy indoor air</h3><p>Two indicators offer a clear window into the health of indoor environments: fine particulate matter (PM2.5) and carbon dioxide (CO₂). To put PM2.5 in perspective, these particles are about 30 times smaller than the width of a human hair, so tiny that thousands could fit across a single strand. PM2.5, microscopic particles small enough to enter the bloodstream, infiltrates indoor spaces from outdoor pollution but is also generated indoors through cooking, dust resuspension, building materials, and combustion sources. Carbon dioxide, meanwhile, is not harmful at typical indoor levels but acts as a critical proxy for ventilation. When CO₂ levels rise, they signal inadequate fresh air exchange and the buildup of pollutants, pathogens, and stale air.</p><p>Research from the Harvard T.H. Chan School of Public Health’s Healthy Buildings program has shown that improved ventilation and filtration can significantly reduce indoor particulate exposure. More strikingly, their work demonstrates that elevated CO₂ and particulate levels impair cognitive function, slow response times, and reduce decision-making performance. In one study, cognitive scores dropped by up to 15% when CO₂ and particulate levels were elevated, compared to well-ventilated conditions. In classrooms, this can influence learning outcomes. In workplaces, it affects productivity and concentration. In homes, it shapes sleep quality, recovery, and overall well-being.</p><p>Indoor air quality is therefore not merely a respiratory health issue. It affects how we think, learn, and perform.</p><h3>India’s built environment challenge</h3><p>India’s built environment presents a complex IAQ challenge. For example, typical indoor PM2.5 concentrations in urban apartments can range from 60–90 µg/m³ on high-pollution days, as outdoor air seeps in through poorly sealed structures. In contrast, few kitchens using biomass fuels in rural areas may experience indoor PM2.5 levels that soar well above 150 µg/m³ during cooking, driven by solid-fuel combustion and dust. High-density living in cities reduces effective ventilation, and the increasing adoption of mechanical systems prioritise thermal comfort and energy consumption over fresh air exchange. This led to a situation that buildings designed to conserve energy without keeping the IAQ as focus can trap pollutants when ventilation is poorly designed. Ironically, buildings rely on energy-inefficient mechanical systems even when outdoor temperatures are comfortable for 25% to 30% of the year. Poor air quality prevents us from using this natural ventilation, forcing a continued dependence on energy-intensive mechanical systems.</p><p>While Indian national policies and actions prescribe the measurements and monitoring at multiple outdoor spatial levels, IAQ measurement and awareness is yet to break the ground. This invisibility has economic consequences as well as health implications. Preliminary research suggests that improving indoor air quality in workplaces and schools can boost cognitive function and productivity, potentially translating into significant gains in GDP over time. For example, a 2020 pilot study in Bengaluru offices reported that installing air filtration systems reduced PM2.5 concentrations and was associated with measurable improvements in employee task performance and reduced absenteeism (Ramachandran et al., 2020). For a country like India, even a 1% boost in workforce productivity through healthier indoor environments could amount to crore of rupees in additional economic output each year. Quantifying and publicising these benefits may help accelerate the adoption of the best practices. </p><p>Market signals suggest that awareness is beginning to shift. In several polluted urban centres, developers are now marketing “low-AQI homes” equipped with filtration systems and controlled ventilation as premium offerings. This reflects a growing recognition that health is becoming a defining metric of built environments. Ensuring access to clean indoor air must be viewed as a fundamental public health necessity rather than an optional luxury. </p><h3>Designing buildings that breathe</h3><p>The first step toward healthier indoor environments is measurement. Cities monitor outdoor air quality in real time; buildings must begin to do the same. Advances in sensor technology now make it possible to continuously track PM2.5, CO₂, temperature, humidity, and ventilation performance. Real-time data allows facility managers to adjust ventilation rates, improve filtration, and respond to pollution spikes. Over time, such monitoring can create benchmarks for healthy buildings, much as water quality standards transformed public health in the twentieth century.</p><p>Improving indoor air does not require futuristic technology. Proven solutions exist: adequate ventilation, high-efficiency filtration, low-emission building materials, source control for indoor pollution, and smart HVAC systems that balance energy efficiency with fresh air exchange. International research suggests that CO₂ levels below 800–1000 ppm typically indicate well-ventilated spaces, while higher levels signal inadequate airflow and potential pollutant buildup.</p><p>In India, where climate extremes and energy constraints shape building operations, the challenge is to balance thermal comfort, energy use, and ventilation. While smart building design—such as mixed-mode ventilation, demand-controlled airflow, and occupancy-aware systems—offers the potential to improve air quality alongside energy efficiency, the practical implementation of these technologies can face significant hurdles. These challenges may include high upfront costs, , complex maintenance, and adaptation of existing infrastructure. While high utility costs are a concern, research shows that smart ventilation systems save money by adjusting airflow based on how many people are in the room. </p><h3>What building-level data is already showing</h3><p>The intersection of indoor air quality, climate adaption, and economic productivity is particularly important for India. Healthier indoor environments can reduce disease burden and healthcare costs, improve cognitive performance and workplace efficiency, and enhance learning outcomes in schools. </p><p>There are early examples demonstrating what this transition can look like. In several Indian cities, building-level monitoring initiatives have begun to track indoor particulate levels and ventilation performance in offices, transport hubs, and public facilities. Real-time environmental monitoring work has shown how building-level PM2.5 and CO₂ tracking can reveal pollution patterns invisible to occupants — from particulate spikes during peak traffic infiltration to elevated CO₂ levels in meeting rooms with poor ventilation. In a study commissioned by Cummins India Foundation and CSIR-NCL based Venture Center Pune – 10 schools in Delhi and Mumbai were found to have over 130 to 230 ug/m3 as average PM2.5 over a month-long evaluation during winter 2026. In one commercial building pilot, ventilation adjustments guided by real-time CO₂ data improved air exchange rates while optimising energy use, highlighting how data-driven management can support both health and efficiency.</p><p>Such interventions remain the exception rather than the norm. But they illustrate a critical point: indoor air quality is measurable, manageable, and improvable.</p><h3>The next frontier of clean air actions</h3><p>Globally, the concept of “healthy buildings” is gaining traction, driven by lessons from the pandemic, workplace productivity research, and rising awareness of environmental health. International climate and health frameworks increasingly recognise the importance of indoor environments in shaping resilience and wellbeing. India, with its scale of urbanisation and infrastructure growth, has an opportunity to integrate IAQ into the future of building design and public health actions.</p><p>The evolution of air quality management will not stop at citywide dashboards. It will extend to the spaces where we spend our lives: homes, classrooms, workplaces, transit systems, and healthcare facilities. Just as clean drinking water became a baseline expectation through actions by government, engineering, and monitoring, clean indoor air must become a design standard rather than a premium feature.</p><p>Because the future of healthy living will not be defined only by the air outside our windows, but by the air inside our buildings.</p><h3> <strong>Author Bio</strong></h3><p>Ronak Sutaria is Founder and CEO of Respirer Living Sciences, an environmental intelligence organisation working at the intersection of air quality, climate sciences, and urban policy.</p><p>Rajan Rawal is a Professor at CEPT University and a senior advisor at the Center for Advanced Research in Building Science and Energy (CARBSE), CEPT Research and Development Foundation (CRDF).</p>