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While air purifiers can improve indoor air quality, their effectiveness in extreme pollution levels like Delhi’s AQI of 400-500 is limited, and proper use and maintenance are key to seeing any benefits.
A thick layer of smog blankets Delhi | Image/File (PTI)
As the Air Quality Index (AQI) in Delhi crossed the hazardous 400 mark earlier this week, many residents are wondering whether air purifiers can provide any relief. While pulmonologists agree that air purifiers can improve indoor air quality by reducing pollutants like dust, pollen, mold spores, and pet dander, their effectiveness diminishes unless certain precautions are followed.
Dr. G.C. Khilnani, Chairman of Pulmonary, Critical Care, and Sleep Medicine at PSRI Hospital, emphasizes that while air purifiers can help reduce indoor pollution, they are not a cure-all. He points out that no scientific studies conclusively demonstrate the health benefits of air purifiers in extreme pollution conditions. For an air purifier to work effectively, it must be used in a closed room, with doors and windows kept shut. Simply placing it in the living room, expecting it to purify the entire house, is unrealistic.
According to Dr. Khilnani, air purifiers typically consist of two key components: a filter that blocks particulate matter (PM 2.5 and PM 10) and an adsorbent that captures harmful gases like NO2 and carbon monoxide. For optimal performance, the air purifier must be of good quality, properly sized for the room, and run continuously. Additionally, the air should be directed toward areas where people sit or sleep to maximize benefits.
Despite these recommendations, Dr. Khilnani is cautious about expecting dramatic results, particularly when AQI levels reach extreme values like 400-500. In such cases, an air purifier might only reduce PM 2.5 levels by a fraction, potentially bringing them down to around 150 after running the unit overnight. While not entirely effective, air purifiers can provide some relief, especially for those with pre-existing respiratory conditions like asthma, COPD, or heart disease.
However, Dr. Khilnani also warns of the risks of improper maintenance. Failing to replace the filter regularly could result in the accumulation of fungi and bacteria, which could cause infections.
In contrast, Dr. Nikhil Modi, a senior consultant in Respiratory and Critical Care, notes that air purifiers equipped with HEPA filters can capture up to 99.97% of particles as small as 0.3 microns. Such models can effectively reduce allergens and irritants that trigger respiratory symptoms. Some air purifiers also come with activated carbon filters, which help remove odors and volatile organic compounds (VOCs) emitted by household products, improving overall air quality.
However, Dr. Modi highlights potential side effects. Some air purifiers, particularly those with ionizers, may emit small amounts of ozone, which can irritate the lungs and worsen asthma or allergy symptoms. To avoid this, he advises choosing models certified by standards like the California Air Resources Board (CARB), which ensures safe ozone levels. Additionally, extended use of air purifiers, especially during the winter, can dry out the air, causing discomfort such as dry skin and mucous membranes. In such cases, a humidifier may be beneficial to restore moisture in the air.
Air purifiers also have maintenance challenges. The heavy load of pollution in high AQI conditions can wear down HEPA filters quickly, reducing their lifespan. While standard filters last between 6-12 months, in highly polluted environments, they may need to be replaced every 1-3 months. For optimal performance, it’s crucial to regularly check the filters and ensure they are not clogged, as this can reduce the purifier’s efficiency or even cause pollutants to re-enter the air.
Dr. Vikas Mittal, a pulmonologist at CK Birla Hospital, suggests that indoor plants like peace lilies, snake plants, and spider plants may help improve air quality by absorbing some pollutants, such as carbon dioxide and certain VOCs. While plants can supplement air purifiers, their effect is minimal when compared to purifiers, especially for fine particulate matter like PM 2.5, which is prevalent in polluted cities. To have a noticeable impact, a large number of plants would be needed, and even then, they cannot eliminate the smallest, most harmful particles.
In summary, while air purifiers can help reduce some pollutants and improve indoor air quality, they are not a perfect solution, particularly during periods of extreme pollution. Proper use, maintenance, and room conditions are essential for getting the most benefit. For those in high-pollution areas like Delhi, air purifiers can offer some relief, especially for individuals with respiratory issues, but they should not be relied upon as the sole measure for combating pollution.