Experts question plan of air purifiers at major Delhi crossings

Experts today questioned Delhi government's plan to install air purifiers in major intersections and termed it as a 'red herring', saying the focus should be on controlling polluting sources.
IIT Delhi Professor Mukesh Khare said no manufacturer of such purifiers have been able to answer the potential capacity, or 'zone of influence' of such devices, especially when installed outdoors.
Anumita Roychowdhury of Centre for Science and Environment (CSE) wondered what difference would such purifiers make in a massively polluted city like Delhi, considering its radius will be around 20-30 metres only.
"What the zone of influence (capacity) of such an air purifier would be is an important question that has not been answered by any manufacturer till date. How is it going to be measured?" Khare asked.

He explained that the capacity of a purifier depends on its pumping velocity and density of pollutants in its immediate surroundings.
"If level of pollutants are very high around prufiers, its filter will get choked very quickly and the pressure will drop and its capacity will decrease," Khare said.

Anumita said New Delhi Municipal Corporation had installed one such device in Connaught Place in 2010 but never released the complete data gathered by it.
"They used to release only the outlet level air quality but not its impact on the surroundings. No one knows how it cleaned the surrounding air," she said.

She said resources should be invested on controlling pollution at the source, like farm fires, vehicle pollution, construction dust considering these devices are also expensive.