India on Wednesday unveiled a new weapon against air pollution — an “anti-smog gun” which authorities hope will clear the skies above New Delhi but which environmentalists say amounts to a band-aid solution.

The cannon's Indian manufacturers say the fine droplets of water it ejects at high speed can flush out deadly airborne pollutants in one of the world's smoggiest capitals.

The giant mister — shaped like a hair dryer and mounted on a flatbed truck — was tested in Anand Vihar, an area of Delhi's east bordering an industrial zone that often boasts the dirtiest air.

The US embassy website on Wednesday showed concentrations of the smallest and most harmful particles known as PM2.5 at Anand Vihar hit 380 — more than 15 times the World Health Organisation's safe maximum.

The cannon — designed to combat dust on mining and construction sites — costs roughly $31,000 but government officials appear ready to open the cheque book. “If it proves to be successful, then we will roll these out on Delhi's streets as soon as possible,” Imran Hussain, Delhi's environment minister, told AFP in Anand Vihar as the cannon spurted mist under hazy skies.

Manufacturer Cloud Tech said it can blast up to 100 litres of water per minute into the skies and clear 95 per cent of airborne pollutants.

Greenpeace was less than impressed, saying the cannon was a distraction from the root causes of Delhi's winter pollution, a phenomenon so bad the city's own chief minister described it as a “gas chamber”.

Delhi chokes every winter as cool air traps a toxic blend of pollutants from crop burning, car exhausts, open fires, construction dust and industrial emissions close to the ground. “This is definitely not the solution. You can use it occasionally at sensitive locations but the solution to pollution lies in controlling it at the source rather than spraying water on it,” Greenpeace's Sunil Dahiya told AFP.

“The Delhi government should look at more sustainable solutions rather than creating business for a few companies.”

Delhi has struggled to curb the annual scourge, with drastic short-term measures — such as shutting factories and brick kilns and restricting car use — failing to lower hazardous pollution levels. The crisis was so serious in November that doctors declared a public health emergency as schools were shut across the capital.

Cloud Tech admitted one or two cannons would do little to combat the city's notorious air, suggesting instead 30 to 40 would be required. “This is a solution for when you're helpless,” the company's Vimal Saini told AFP.

Beijing experimented with a mist cannon in 2014 but critics slammed officials for wasting money on a machine that scientists agreed did little to lower pollutants.