Beijing promised harsher punishments on Thursday for those responsible for noxious air pollution, as residents breathed a sigh of relief after the thick smog that had shrouded the city for a week dissipated.

The capital will outline stricter and more detailed punishments for violators of the Beijing Air Pollution Prevention Regulation, which will come into effect on March 1.

The regulation will give more authority to environmental departments, said Yan Xiangyang, deputy head of the environmental monitoring team of the Beijing Environmental Protection Bureau.

The regulation, which marks the first time that the city has made air pollution reduction the law, was passed by the city's legislature at the end of its people's congress plenary session. The regulation imposes harsher fines and penalties against violators, Yan said.

Enterprises that discharge pollutants on the roadside without permission will face a fine of up to 200,000 yuan ($32,640), up from 50,000 yuan, the bureau said.

Polluting enterprises that refuse to reduce or suspend their production during serious or severe pollution will be fined up to 500,000 yuan, up from 100,000 yuan.

Repeat offenders will face double punishments after each violation, with no limit on the amount of the fine, it said.

In addition to the fines, enterprises that violate the regulation will have the incidents added to their credit records — a sanction that is expected to lead to more industry self-policing, experts said.

Chai Hefa, chief climate expert at the China Research Academy of Environmental Sciences, applauded the regulation. The credit sanctions are expected to raise the awareness of polluting enterprises and help further reduce polluting emissions, he said.

The monitoring team has inspected more than 900 coal-fired electricity plants since Nov 15, when the city kicked off its heating season and saw more air pollution.

About 80 enterprises were found to have excessive polluting emissions, mostly sulfur dioxide and nitrogen dioxide, and were fined a total of 1.53 million yuan, the monitoring team said.

Beijing has just experienced the longest stretch of smog since it started monitoring the level of PM2.5, or particulate matter with a diameter less than 2.5 micrograms.

The pollution alert was lifted at the stroke of midnight Thursday morning, as a strong cold front finally dispersed the smog that had enveloped the city since Feb 20.

Residents were so happy that many resumed their outdoor activities and posted pictures online of the long-awaited blue sky.

"It's great to breathe without a mask again," said Li Jun, a 27-year-old resident of Chaoyang district. "You learned not to take anything for granted."

The environmental bureau said members of the public can dial the bureau's hotline, 12369, to report violations of the pollution regulation.