How do smog towers work?

Smog towers have been in the news lately after Delhi Chief Minister Arvind Kejriwal inaugurated one such unit in the national capital. Delhi — infamous for its winter smog — could see more smog towers across the city if the pilot project in Connaught Place yields good results, Kejriwal said during the launch.

The recently-installed tower stands 24 metres tall and is fitted with 40 fans and about 5,000 filters. But how exactly does it work?

To start with, smog towers largely tend to follow two systems: an 'updraft air cleaning system' and a 'downdraft air cleaning system.' Delhi's newly-inauguarted smog tower uses a downdraft air cleaning system. What this means is that the tower sucks in polluted air from above, sends it down to the 5,000 filters, and clean air is then distributed 10 metres above ground level by the 40 fans (10 on each direction).

The first step of this process begins with the fans at the top of the towers, which when operational create a negative pressure that helps suck the polluted air from above into the tower. Following this, the filters with macro and micro layers — trap particles of 10 microns and larger, and particles of around 0.3 microns, respectively. It is after this that the filtered air is released at a rate of 1,000 cubic metres per second.

The Connaught Place smog tower will only operate in full capacity after the monsoon season, Delhi Environment Minister Gopal Rai said.

Developed by IIT Delhi and Bombay, in collaboration with the University of Minnesota, the smog tower is expected to improve the air quality within an area of 1 sq kilometre of the unit. Apart from filtering polluted air, the tower will also monitor air quality using an automated Supervisory Control and Data Acquisition (SCADA) system, as per a report by The Indian Express.

Built at a cost of Rs 20 crore, the impact of the tower on air quality will be known fully to researchers only after two years.

Many experts have already pointed out that smog towers are a costly quick-fix measure with no scientific evidence to back their efficacy in the long term. Only time will tell whether the smog tower is effective or not.

(With agency inputs)