Home >Lounge >Features >Unseen 2019: Living in a carbon dioxide bubble

It’s a cold December morning and students of the Ardee School in Delhi’s New Friends Colony area are rushing indoors. It is, in terms of air quality, a “red flag" day at the school—no outdoor activities are allowed and anti-pollution masks must be worn at all times. The air quality index (AQI) in the city has dipped to “hazardous" levels.

Inside a classroom with around a dozen seven-year-olds, Jai Dhar Gupta, founder of the clean air solutions company Nirvana Being, shows me a small device fitted to one of the walls. Called Ventimax, it pulls in filtered ambient air from outside to tackle a pollutant in indoor air, in spaces like classrooms, residential and office buildings, which often goes unnoticed: carbon dioxide (CO2).

The battle to curb air pollution continued in 2019 as ambient AQI levels in Delhi, the National Capital Region (NCR) and north India hit a record high. Particulate matter (PM) levels in the air were much higher than prescribed by the World Health Organization. But there was little documentation when it came to the rising indoor levels of carbon dioxide in Delhi.

Graphic: Ahmed Raza Khan/Mint
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Graphic: Ahmed Raza Khan/Mint

Yet multiple studies and research papers released recently in India and globally have shown the direct health hazards associated with prolonged exposure to atmospheric and indoor carbon dioxide. CO2 is a natural by-product of human metabolism but when the body is exposed to high levels of this colourless, odourless gas for prolonged periods indoors, it can be damaging.

It’s confusing, however, because levels may vary depending on the number of people in a room/building, the use, the ventilation. The global average for outdoor CO2 levels is pegged at 407 ppm (parts per million). CO2 concentrations higher than 1,000 ppm indoors are considered harmful, though the latest evidence suggests even lower levels could be dangerous.

There are six adults in the classroom, apart from the children, when we inspect the device, which Gupta is testing as part of a pilot programme. A smartphone app synced to the device shows indoor CO2 levels at 900 ppm. Some of the children run around as a break approaches—they are exhaling more and more CO2. Isn’t 900 ppm high? I ask. “This is good," says Gupta, explaining that the recently-launched device, starting at 24,990, creates a positive air pressure in the room, pushing stale air and CO2 out. Standing outside the class, we can feel a draft flowing through the gaps around the door.

According to the indoor environment quality standards recommended by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (Ashrae) Standard 62.1-2013,indoor CO2 concentrations should remain less than 700 ppm above outdoor concentrations for “occupant satisfaction and comfort". In its latest standards, Ishrae—the American Society’s India affiliate—lists the threshold values for indoor CO2 levels at “ambient + 350 ppm". So, if CO2 levels in the ambient air are at, say, 400 ppm (CO2 concentrations in outdoor air typically range from 300-500 ppm), then the levels indoors should not go beyond 750. The same principle applies to the Ashrae standard.

Given the conditions outside, Gupta says 900 ppm is not bad. Once the class ends, the students leave for breakfast, which takes the CO2 level back into the 800 ppm range. An air quality monitor on the teacher’s desk shows CO2 levels are “good". “We are already in high PM 2.5 levels. When you add (indoor) CO2 to it, our children don’t stand a chance," says Gupta. “As CO2 build-up happens in a classroom, the children will start to feel drowsy and their cognitive abilities will diminish with every passing second," he adds. A spokesperson for the school tells me they were receiving complaints of headaches from students. They knew it was probably because of the air, but “never associated it with the CO2 levels".


In a study published in July, researchers from Northwestern University, Chicago, University of Michigan and University of Wisconsin-Madison reviewed preliminary evidence on the potential health risks of chronic exposure to “environmentally relevant elevations" in ambient CO2. This included inflammation, reductions in higher-level cognitive abilities, bone demineralization, kidney calcification and oxidative stress. “This early evidence indicates potential health risks at CO2 exposures as low as 1,000 ppm—a threshold that is already exceeded in many indoor environments," said the study, which was published in the journal Nature Sustainability.

The researchers reviewed existing data from different fields—physiology, immunology, environmental health, cognitive psychology and building engineering. They also cited recent data which showed an increase in serum bicarbonate (a form of CO2 in the blood) levels among the general US population, possibly driven by increased exposure to the gas.

The study explains how air conditioning, “influences" individual CO2 exposure. CO2 is a dense gas which tends to concentrate at lower elevations. Most air-conditioning units ventilate air closer to the ceiling, introducing CO2 into rooms more quickly than they remove it. Another source of exposure, according to the study, is sedentary desk work under normal office conditions, which results in relatively static air and less occupant movement. These conditions can result in higher CO2 concentrations around the nose and mouth, causing occupants to “rebreathe" their own exhaled CO2. “Personal CO2 bubbles can average 1,200 ppm (compared to 650 ppm in the surrounding indoor air) under normal ventilation conditions in an office-like environment," the study adds.

To understand how one can monitor these personal CO2 levels, I meet Nita Soans, India CEO of the air quality monitoring and solutions company Kaiterra, at her office in south Delhi. Kaiterra launched a CO2 variant of its Laser Egg air quality monitor in September. With just three people in a relatively spacious meeting room, the CO2 levels spike—1,800 ppm, the AQ monitor says in striking red font. Soans walks towards a door to show how a little ventilation could fix this. She places a metal wedge between the door as we resume talking.

“A lot of the people I know had no idea about the CO2 levels in their rooms. I think it is useful to be aware and realizing things like why I was getting out of bed feeling very sluggish," says Soans.

“Schools and offices are closed areas that have several people sitting in one enclosed space, spitting out more carbon dioxide. I have seen office spaces and multinational corporations that had CO2 levels of 2,500-2,800 ppm, which is insanely high. Many workspaces are functioning at levels between 2,000-3,000 ppm. A lot of productivity is going down because of this," she explains. “There’s value in having a healthy working environment and some companies do realize that there’s an RoI (return on investment) on having clean air systems."

By the time our conversation ends, the CO2 levels in the room have come down from 1,800 ppm to 1,270 ppm, thanks to the open door. The PM 2.5 levels, however, have gone up. It is tricky to maintain a balance between CO2 levels and particulate matter.


“I call it a see-saw effect," says Barun Aggarwal, CEO of the indoor air quality solutions provider Breathe Easy Consultants.

Aggarwal says windows and doors are being made tighter in new homes, limiting the exchange of air and natural ventilation. “When you tight-seal a place, CO2 levels will go up to 3,000 ppm. If the windows in the same space are leaky, the levels won’t go above 1,500-1,600," he adds. Air purifiers and open windows could be a solution. It might be possible to get optimal levels of less PM and CO2 in some cases, he says.

The company is the official partner of Swiss firm IQAir, which offers a ventilation solution similar to Ventimax. “Essentially, it’s an air purifier which constantly brings outside air inside," says Aggarwal.

Having constantly recorded CO2 levels of 2,800 ppm in his room at night, Aggarwal was looking for a solution when he came across the IQAir HealthPro 250 (with a special ducting system) at IQAir’s headquarters in Zurich. “I tested the machine at my home for a year. It controls both CO2 levels and PM 2.5 particles…. Hundreds of people have it now. It is expensive (at 1.5 lakh) but there’s a cost to clean air," he adds.

Aggarwal, who is also on Ishrae’s indoor environment quality committee, was the co-author of a study, released in July, based on tests conducted by the company in more than 400 Delhi-NCR homes. The tests, based on existing data, looked for three of the most “harmful" indoor air pollutants: PM 2.5, total volatile organic compounds (TVOCs) and CO2. Findings on CO2 were analysed by segregating the collected AQ data into three categories: “occupied homes with air purification (doors and windows closed)", “occupied homes without air purification (doors and windows closed)" and “occupied homes without air purification (doors and windows open)". Doors and windows are indicators of ventilation.

When the data for the last category of homes was analysed, the average CO2 concentration was found to be 600 ppm, well within the standard recommendation. On the other hand, the CO2 concentration of a typical “air-conditioned closed-door bedroom tends to peak at 3,000 ppm with two occupants inside it" after 8 hours, mostly at dawn.

Aggarwal describes CO2 as a pollutant that has gone unnoticed and has a “big impact on quality of life".“There are two-three reasons I would say it has gone unnoticed. The awareness about the problem is very low. It’s also about the numbers. You can’t fix what you can’t measure," he says. “Earlier, measuring these pollutants was challenging because you didn’t have consumer grade equipment to measure them.... Another recent phenomenon is that slowly, as newer homes are being built, windows and doors are being made tighter. We are boxing ourselves," he adds.

In 2017, Arindam Datta, a fellow with The Energy and Resources Institute’s earth science and climate change division, was the corresponding author of a study, published in the International Journal Of Sustainable Built Environment, conducted in two offices and one educational building in Delhi. The three major pollutants were measured, using sensor-based equipment, inside each building at a 5-minute interval between 9.30am-5.30pm for five days every week from June-July 2015. The CO2 results varied—average concentrations were high in the office buildings, less in the educational building—due to different working hours and visitor movement.

“We have to look at indoor air first, but ambient air plays a major role in your indoor air quality also," says Datta. “Carbon dioxide is more relevant in an urban set-up. Apart from office buildings, there are malls and hospitals that have centralized air-conditioning systems. If that system is not working properly, without proper ventilation of air from the outside, then it will create Sick Building Syndrome," he explains, adding that regulatory focus is centred only on ambient air pollution. Rising CO2 levels in indoor air are not a point of concern right now.

As the study published in Nature Sustainability explains, average indoor CO2 concentrations in offices, schools and homes can exceed 2,000 ppm not only because of increased room occupancy but reduced building ventilation rates. Building ventilation rates may be reduced to conserve energy, slow down climate change and avoid conveying outdoor air pollutants indoors, thereby increasing indoor CO2 concentration, the study adds.

Karthik Ganesan, a research fellow at the Council on Energy, Environment and Water, a Delhi-based think tank, says there’s a need for fresh air to be part and parcel of HVAC (heating, ventilation and air conditioning) systems in buildings; it shouldn’t be seen as an additional cost. “Better thermal comfort does not excessively rely on air-conditioning-based solutions. That’s how many fantastic buildings are actually designed. A building that is actually designed for thermal comfort has a lot of places where fresh air gets in," he adds.

Ganesan regularly measures the CO2 levels in his office. While we speak over the phone, he tells me the readings are at 1,750 ppm. “That’s because right now we are in an environment where we are running air purifiers. We are limiting the amount of openings we have (in the building)," he says. “Fresh air intake is easier said than done. It requires amendments to be made to the design of a building, like making incisions to the facade of a building, which many building regulations do not permit," he explains.

Good air, says Ganesan, is “only affordable when you treat it at source," he adds. “Many of these (ventilation) solutions are not catering to everyone. A solution for the masses is well-designed, well-ventilated buildings."

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