Explanation:

The Delhi government has introduced anti-smog guns to tackle the increasing pollution levels in Delhi.
Anti-smog gun is a device that sprays atomized water into the atmosphere to reduce air pollution.

Connected to a water tank and mounted on a vehicle, the device could be taken across the city to spray water to settle dust and other suspended particles.
The theory is that the sprayed water will cling on to the pollutants — particularly particulate matter PM2.5 and PM10 — and wash it down creating the effect of rain.
This could be of use in an arid place like Delhi. But, a place where the climate is already monsoon type or equatorial, rain fall washes away PM in the air. Anti-smog gun is not needed.