To battle Delhi's toxic air, the Central government bought 140 air purifiers worth Rs 3.6 million between 2014 and 2017, according to government data reviewed by Reuters.

Twenty-five of the 140 air purifiers are being used in the PM Office. The Union Government spent Rs 3.6 million, or about $55,000, to buy the air purifiers, as per the data.

Besides the PMO inside the Parliament, the other agencies where the new air purifiers are installed are economic planning think tank NITI Aayog and the ministries of health, agriculture, tourism, home affairs and foreign affairs.

The PM Office and the six departments for which data was available did not respond to queries.

According to the data, the home ministry spent about $20,000 in the last three years to buy 44 of the devices. The 25 air purifiers installed in the PMO cost about $11,000.

Growing air pollution crisis

Delhi Chief Minister Arvind Kejriwal had called the city a "gas chamber" in 2017 as levels of airborne PM 2.5 -- tiny particulate matter that can reach deep into the lungs -- far exceeded levels classified as "hazardous".

A British medical journal, The Lancet, has estimated air pollution was responsible for almost 10 per cent of the total disease burden in India in 2016.

Each year, when pollution levels shoot up in the winter months, the capital's schools are often forced to shut.

Last year, all schools in Delhi were closed for five days due to sky-high air pollution levels.

A federal body that manages more than 45 government schools in the capital said it had made no purchases of air purifiers and had no plans to do so.

Santosh Kumar Mall, the commissioner of the body, Kendriya Vidyalaya Sangathan, said: Offices are generally air conditioned, so air purifiers will function. Our schools aren't air conditioned, windows are open, so air purifiers won't make a difference.

Asked if any steps were taken to safeguard school students from Delhi's dirty air, Mall said: "I don't think so. When pollution increased a lot, our schools were shut."

(An earlier version of the story has been corrected as it contained incorrect information)