Life has turned upside down for Delhi residents as the air pollution level soars in India’s capital. Primary school students and college-goers returned to virtual classes, as during the COVID-19 lockdowns, while professionals who can work from home do so to protect their health. Gig workers and others with fewer protections face the challenge of maintaining their normal routines, while fearing they or their loved ones might end up in the hospital. Exercise routines have been suspended to limit exposure to toxic air, and GRAP (Graded Response Action Plan) Stage IV restrictions were implemented earlier this month.

On November 18, Dr. Shashi Tharoor, the Indian National Congress MP for Thiruvananthapuram, posted a graphic on X, showing Delhi as the most polluted major city in the world. He questioned, “Should it even remain the nation’s capital?” sparking mixed reactions online.

Mr. Haider Ali Khan, a journalist who works in Delhi, said the city’s air pollution has drastically affected visibility and health.

“The air pollution is making Delhiites choke every second,” he noted, pointing out widespread coughing, sneezing, throat clearing, and complaints of burning eyes.

Mr. Jude Francis Weston, a fellow journalist who commutes from Faridabad to Delhi, described a sharp decline in air quality on November 17 (AQI above 450), which made driving risky due to dense smog and poor visibility.

Even those who can afford to stay indoors are confined to rooms with air purifiers, trying to minimize their movement. But do these devices actually work?

Amazon India shows that thousands of air purifiers have been bought in the past month | Photo Credit: Amazon India

Do air purifiers help?

At the heart of an effective air purifier is a HEPA (High Efficiency Particulate Air) filter, capable of removing 99.97% of airborne particles as small as 0.3 microns. Air purifiers come in diverse forms, from portable devices for cars to high-end models with Wi-Fi integration and real-time AQI reports. Popular brands in India include Dyson, PHILIPS, Quobo, Honeywell, and Xiaomi. Thousands of units have been purchased recently, as people braced for the winter’s toxic mix of Diwali firecracker fumes, agricultural stubble burning, and smog.

For instance, a basic Honeywell air purifier costs under ₹10,000, offering simple air quality colour indicators, while a premium Dyson model (over ₹25,000) provides detailed AQI reports, a smartphone app, and stylish designs. However, many smaller or low-cost air purifiers struggle to handle high pollution levels, with numerous negative reviews citing devices failing to reduce the AQI despite hours of use.

Dr. Kamran Ali, lead thoracic surgeon at Max Super Speciality Hospital, emphasised that air purifiers are most effective when matched to the room size.

“Air purifiers work best if the room is a closed space. The moment you open the room to the balcony or other rooms, some amount of polluted air from outside will come inside,” said Dr. Ali.

He advises using purifiers in rooms with children, the elderly, or those with lung conditions. Regular maintenance, including filter replacement, is also crucial.

Alex Hudson, an engineer at Dyson, explained that air purifiers with HEPA and activated carbon filters can capture particles, VOCs, bacteria, and even viruses. “Outdoor pollutants like vehicle exhaust, pollen, and mold spores can easily enter homes through open windows,” he said. Sealing windows can help, but can also trap indoor pollutants, worsening air quality.

Indoor air pollution is another significant issue, stemming from activities like cooking with gas stoves, cleaning with harsh chemicals, and not properly dusting, said Dr. Ali. He pointed out that many fail to consider the impact of indoor pollutants, which can be just as harmful as outdoor air.

While air purifiers can help reduce pollutants indoors, they are not a one-time fix. Frequent filter replacements are essential, especially in highly polluted areas. Mr. Khan noted that his air purifier, from an American brand, is effective in the area it is placed but less so in other parts of the house.

Mr. Weston, who also uses an air purifier, observed that stepping outside after using one indoors makes the pollution feel even more unbearable. “Without one, it feels like a gas chamber,” he said. Some air purifier companies offer features like timers, quieter modes, and automatic speed adjustments to ease the burden of constant use.

For Delhi residents, wearing masks outdoors has become common again. Dyson has even launched the Dyson Zone headphones, with an attachable air filtration visor that claims to remove 99% of ultrafine particles. However, at ₹64,900, it’s pricier than many home air purifiers.

Mr. Hudson suggests additional measures, such as keeping doors closed, vacuuming regularly, avoiding excessive cleaning chemicals, and using scented products sparingly.

Despite these efforts, Mr. Khan feels stronger measures may be needed.

“I may plan to take leave and move out of the city for the time being,” he said, highlighting the severe health risks posed by the pollution.

Mr. Weston called for greater government action: “It’s time for policymakers to invest in technologies that can effectively address this growing issue.”