In September, Delhi environment minister Gopal Rai made ASGs mandatory for all construction sites in Delhi with an area over 5,000sqm, with one such device to be installed for every increase in 5,000sqm of area.
It’s that time of the year in Delhi when the air would be covered with thick smog and breathing would once again mean intaking pollutants. While the festive mood of Diwali is set to overtake our concern about health and respiratory issues, the Delhi government has doubled down its efforts on having cleaner air. Vehicle-mounted ‘anti-smog’ guns (ASG) have begun doing rounds in the national capital in an effort to disperse the settled dust particles in the air.
Anti-smog guns, which are part of the civic body’s winter-action plan, come along with a ban on firecrackers to keep a check on the rising levels of pollution in the city ahead of winter. Hence, this year, Delhi is gearing itself up with more ASGs, than ever before, to combat pollution.
Anti-smog guns are water cannons used to disperse the suspended dust particles that are settled in the air to form thick smog. The gun is connected to a water tank that is mounted on a vehicle.
ASGs can spray 30-100 litres of water in a minute and the water, which passes through high-pressure propellers, is converted into a fine spray with the size of droplets ranging from 50-100 microns.
Also called spray guns and mist guns, they bind dust particles, PM2.5, PM10 and other pollutants and bring them down to the ground level.
It works through a canopy effect just like rain to bring down the suspended particles wafting in the atmosphere. Treated sewage water should not be used in the anti-smog gun, the guidelines say.
Most recently ASGs were used following the demolition of Noida’s twin towers. However, the impact of ASGs still remains debated by scientists. Experts believe that the impact of ASGs is limited and there has been no scientific study to prove their efficacy in terms of controlling the levels of pollution.
In an interview with Indian Express, Dipankar Saha, former head of the Central Pollution Control Board’s (CPCB) air laboratory, said that ASGs are not the permanent solution when it comes to reducing air pollution. He further said that it may be used along the roadside to reduce particulate pollution or use in any emergency case, but it cannot be sprayed across the city to reduce pollution.
Further, Vivek Chattopadhyay, senior program manager for Clean Air and Sustainable Mobility at the Centre for Science and Environment (CSE) was quoted as saying by PTI,
“The range of such devices is very limited. It affects if at all, the air volume of the immediate surroundings where the spraying is done. The effect diminishes after the spraying is stopped,”
Saha also emphasised “monitoring” the operation of ASGs to see whether it’s truly effective or it’s just another eyewash.
Experts have also suggested that its impact is felt much better inside a closed space than in an open area.
Others also believe that the humidification from spraying ASGs may make the particles grow bigger in size. However, more evidence is required to wholly substantiate this fact.
In November 2019, the Supreme Court asked the CPCB to submit a report ascertaining the efficacy of anti-smog guns. After inspection, the apex court in a January 2020 order mandated the use of the ASGs at large construction sites, road construction stretches and dust-prone traffic corridors.
In Delhi, ASGs were first tested in 2017 and since then, the same has been installed in many key locations across the national capital.
In September, Delhi environment minister Gopal Rai made ASGs mandatory for all construction sites in Delhi with an area over 5,000sqm, with one such device to be installed for every increase in 5,000sqm of area.
Rai said, “In Delhi, earlier it was mandatory to install an anti-smog gun on sites with an area greater than 20,000sqm, but now there is a modification in this provision and construction sites with an area over 5,000sqm will also need to install anti-smog guns. For every 5,000sqm increase in area, an additional smog gun will be required.”
Besides being used on roads, anti-smog guns have also been placed on top of 10 buildings of around seven to ten storeys in the National Capital.
This winter, the city will have more anti-smog guns than in previous years. In 2020, 23 anti-smog guns were installed by the public works department at busy traffic intersections, while 20 such devices were used in 2021 winter.