The new technique of spraying dry ice or cold water into the air was first used last year and is still in its testing stages.

Thailand’s Prime Minister Paetongtarn Shinawatra has ordered free public transport in Bangkok for one week, starting on Feb. 25, in a move to deal with the alarming air pollution in the capital city.

Air pollution in the Thai capital forced more than 350 schools to close on Friday, city authorities said, the highest number in five years.Bangkok officials also announced free public transport for a week in a bid to reduce traffic in a city notorious for noxious exhaust fumes.