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As the BBC's Vikas Pandey reports, rising levels of contaminated water are prompting panic residents in Delhi, the Indian capital, to queue up to buy masks, causing shortages across the city.
"I'm going to wait all day, but I'm not going to buy masks today," shouted an angry customer, a clerk at the Delhi Khan Market Mall.
When the clerk tried to appease the angry customers, others joined the commotion, some of whom had waited more than two hours to buy the mask.
The store that sells high prices
The End masks brand is out of stock and the customer is told to wait until the afternoon.
Masks are usually available in a variety of colors and designs, but with the stock selling, people are happy to be content with anything they can get.
Jai Dhar Gupta, who imported the Vogel mask in South Asia, said he has been trying to meet demand this year.
Mr. Gupta added: "We get stocks from stores in Singapore and Hong Kong, but we still can't meet the demand . " He is also an environmental activist.
"In the last 10 days we have sold thousands of masks because the levels of pollution are much higher than we expected this year.
"The queue is not just on the ground.
Online retailers are also facing huge demand, extending delivery time from a few days to a few weeks.
People's desperation is not hard to understand, as the level of pollution in Delhi has been shocking in recent days.
Tiny particles (known as PM 2. 5)
Last week, the substance entering the lungs reached 800 micrograms per cubic meter.
This is 30 times the average guidelines set by the World Health Organization (WHO)
An average of 25 micrograms per cubic meter, more than 24-hour period.
Schools have been closed and people are advised to work from home.
Most people say they have no choice but to buy masks and air purifiers.
"What else can I do?
The government has not done anything to protect us, so I will do my best to protect my family.
I started buying masks for my whole family, "said Mr. ityunjay Kumar, a lawyer.
Mr Gupta was as upset as Mr Kumar was.
"The government has not taken simple measures, such as banning firecrackers, diesel cars and punishing farmers who burn agricultural waste," Gupta added . ".
"I think someone has launched a chemical war in this city.
"Foreigners living in the city are also queuing up in shops to buy masks.
Josh Hoffman, a longtime US citizen living in Delhi, said the air was "particularly toxic this year ".
"I ride a motorcycle and I think the mask can help me and that's why I'm standing on this line," he said . ".
But can masks and air purifiers solve the pollution problem in Delhi?
"No, these things can only bring temporary relief, not everyone can afford.
We need a permanent solution that first educate the public about the harmful effects of breathing this air, "says environmental activist Barun Aggarwal, who also imports and sells Cambridge masks in India.
People "don't understand that toxic air can cause lung cancer and other deadly diseases," he added ".
"We need to educate the public so they take action like not buying diesel cars and cutting down trees," he said . ".
Mr Aggarwal agreed that the air quality in Delhi is deteriorating every year in the winter, but added that "we are not breathing clean air for the rest of the Year ".
His company is also facing a lot of demand for masks, but he is "not satisfied" with it ".
"You may find this strange.
But I think we need to go beyond air purifiers and masks.
Take the air purifier as an example, the filter will be blocked within a year and will become unusable.
"In most cases they are burned down, causing more pollution," he said . ".
The government needs to find a permanent solution to the pollution problem in Delhi, otherwise the queue at the mask shop will not arrive anywhere soon.