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Mr VN Garg

TreeTake is a monthly bilingual colour magazine on environment that is fully committed to serving Mother Nature with well researched, interactive and engaging articles and lots of interesting info.

Mr VN Garg

Mr VN Garg

Mr VN Garg

Expert Expressions

Smog towers are a waste of money while air purifiers are expensive

Health of citizens, especially in North India, is at risk due to air pollution. What immediate remedies are available to citizens? For outdoor air pollution, Smog Towers and Anti–smog Guns, and for indoor air pollution, Room Air Purifiers have been suggested. But do they really protect us from the ill effects of air pollution?

The Supreme Court of India, in an order on November 25, 2019 directed the Central Government to install Smog Towers, Anti Smog Guns to curb pollution in Delhi.  A Smog tower is a large (the size of a skyscraper), vertical structure designed as a large–scale air purifier to reduce air pollution particles in the air outside. The Ant-smog Gun is a cannon shaped device that sprays atomized water droplets in the air. The gun is attached to a water tank built on a movable vehicle, which can be taken to various parts of the city. The Smog tower shot to fame when it was built and installed in China’s Xi’an city. Room Air Purifier, on the other hand, is a   device meant to purify air inside a closed room. It usually consists of a filter or multiple filters and a fan that sucks in and circulates air. As air moves through the filter, pollutants and particles are captured and the clean air is pushed back into the living space. Typically, filters are made of paper, fibre, or mesh, and require regular replacement to maintain efficiency. Once considered an extravagance, room air purifiers are now fast becoming a daily necessity. These are being deployed in households, kitchens, workplaces and also in businesses that receive customers.

Many people argue that certain plant species are a good substitute for room air purifiers. This is not correct. Plants do help a little bit by removing carbon monoxide in the air but the plants cannot filter out particulate matter (PM), the latter being more harmful to health. Plants    cannot remove particulate matter as well as indoor pollutants like Nitrogen dioxide and Formaldehyde. Some other people argue that salt lamps absorb particulate matter and dust but there is no research study to support such claims. The fact remains that when outdoor air quality is poor, room air purifier is our best bet.

The use of room air purifiers is increasing all over the world. For example, in South Korea, more than 2 million air purifiers are estimated to have been sold in   one year (2018). This is more than four times higher than the roughly 5 lakh units sold in 2014, according to market watchers. Companies like Samsung and LG Electronic co are innovating to offer all-in-one solution for pure air, by introducing artificial intelligence-based air conditioners that can purify air. In India, between 2014 and 2017, a total of 140 air purifiers costing around Rs 36 lakh were purchased for PM’s offices, and agencies like NITI Aayog, and the ministries of health, agriculture, tourism, home affairs and foreign affairs of the Government of India. There is need to launch a project for schools and public facilities providing air purifying systems in their premises. We also need to identify the effect of fine dust on students and develop school dust management systems. Functionality of air purifiers is designed to capture dust particles, PM and pollen but is limited in terms of filtering out gases, VOCs or Radon. Further, filters should be frequently replaced for optimal efficiency, usually about every three months or so. HEPA is High Efficiency Particulate Air. HEPA filters are made of very fine fibre glass thread. If a person is suffering from allergy or asthma, an air purifier with HEPA filter may be helpful, as it will be good for removing fine airborne particulate matter.

Another key element while choosing an air purifier is the device’s CADR (Clean Air Delivery Rate) which refers to how much clean air the device can filter out in a unit of time. That relates to the size of the room where the device is placed. The bigger the room, the bigger should be the air purifier. A 120 square feet room requires an air purifier with a tobacco smoke CADR of at least 80. In other words, the air purifier’s tobacco CADR, printed on the device’s box, and should be two thirds of the room’s area. If a room has a size of 450 sq feet, the tobacco CADR of purifier should be 300.

Most particulate matter is in the early morning due to morning commute of trucks carrying   load and goods.  This gets worse in winters when pollutant concentration increases. In North India, stubble burning in paddy fields causes still higher levels of air pollution in winters. It is obvious that room air purifiers can be of great help in protecting the health of citizens, especially of old persons and children. Children are at risk of leukemia, impaired cognitive development and strokes. Air quality varies throughout the day. It is recommended to run air purifiers at their highest speed for half an hour to an hour, which brings pollutant levels quickly. Then it can be switched on to its lowest setting, to maintain that level of air quality. At night, it is advisable to run it at the lowest speed because it is noisy at high speeds.

The situation in respect of Smog Towers is very different, as compared to the room air purifiers. There is a controversy about the efficacy of smog towers/ outdoor air purifiers to clean the air in our external environment. The argument is that PM2.5 pollutants in external environmental air   can only be controlled by eliminating emissions at sources. The capacity of a typical smog tower is 4, 60,000 cubic metres per hour. This can purify only a miniscule of atmospheric air every hour. The smog towers are inefficient, expensive and a waste of money. Measures such as smog towers and anti smog guns are quick fixes, and they give citizens a false sense of security that pollution is going away. And governments can get political mileage by saying that they are seriously solving the problem of pollution. Smog Towers can, at the most become a means of spreading awareness about air pollution. In Bengaluru, Delhi and Mumbai, smog towers placed on roads and busy traffic intersections   are likely to result in waste of public resources, with no impact on air pollution. Probably, experts need to advice courts also in this area. Even masks do not provide real protection from pollution. Masks are at the most a psychological means to provide assurance to the citizens against pollution. The same is the case in respect of Anti Smog Guns.

In a nutshell, while indoor air purifiers do provide protection against PM 2.5 air pollutants inside enclosed spaces, smog towers are ineffective to protect citizens from air pollution outside. There is no substitute for controlling air pollution at source. We must enforce emission standards in vehicles and factories, replace fossil fuels by clean fuels, encourage solar and wind energy and eliminate stubble burning, to reduce and control air pollution.

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