New Delhi, (IANS) With Delhi witnessing poorest air quality of the season, the sale of air mask has increased over 70 per cent in the last two-three days with many chemist outlets in the city reporting that stocks have ben sold out.

Chemist outlet owners across the city on Sunday said that unlike in the past, N-99 masks were most in demand though they are priced around Rs 2,000 apiece.

"We have never ever recorded such high sale of masks. Situation is such that after Diwali, every day we are compelled to place orders for more masks from suppliers to meet customer's need," Ajit Rai, a worker with south Delhi-based Religare Wellness Pharmacies, told IANS.

"Keeping in mind the air quality, people are mostly seeking the N-99 mask which assures the best protection in comparison to other ones such as N-95 and routine ones," he said.

Explaining the types of mask, Rai said that the difference between an N-95 and N-99 masks is the efficiency level of the filter.

"The N-95 mask ispriced at Rs 150-200 and has three layers of filter, while N-99 has more than that and priced Rs 2,000-2,200. There are routine masks as well which are the most simple one and available at Rs 5-10," he added.

Ranjeet Kumar of Baxico, a chemist outlet in South Delhi's Lajpat Nagar, told IANS that his customers were mostly opting for the N-95 and N-99 masks.

"We sold around 100 N-99 masks today (Sunday) in comparison to none before Diwali. Observing the rising demand for the last couple of days, we have decided to increase the stock," Kumar told IANS.

Delhi on Saturday saw the worst air pollution of the season. The smog that hung low over the city kept pollution levels extremely high breaching the safe limit by over 17 times at several places.

The National Cancer Registry has revealed that incidents of lung cancers Delhi have increased by over 33.3 per cent since the middle of last decade in Delhi.

The survey conducted by Centre for Science and Environment in June 2016 also stated that particulate matter, nitrogen oxides and ozone were high and increasing in Delhi's air.