The new legislation prohibits smoking in all indoor public places, including offices, shopping malls and airports, as well as at outdoor stadiums, school grounds and public parks.
More than 1,000 inspectors were today sent to government agencies, hospitals, schools, hotels and other places to ensure the law is followed.
The officials found cigarette butts in hotpot restaurant's washroom, with the restaurant failing to publicise the smoking complaint hotline 12320 on its no-smoking posters, state-run Xinhua news agency reported.
Individuals caught smoking in public places may be fined 200 yuan (USD 32), while businesses will have to pay up to 100,000 yuan for failing to prevent smoking on their premises.
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Venues which repeatedly ignore the law could have their licenses revoked.
As the world's largest tobacco maker and consumer, China has more than 300 million smokers, almost the size of the US population, and another 740 million people are exposed to secondhand smoke.
At Beijing Capital International Airport, people gathered at two designated outdoor smoking areas to have a puff as indoor smoking rooms at the airport's three terminals have all been closed.
A report on the state-run CCTV said there is a widespread scepticism about the ban as smoking has been ingrained in Chinese families for long.
While regulators have vowed strict implementation, some still doubt the feasibility of the ban and fear authorities' resolve to curb smoking could taper over time and leave the ban as ineffective as its predecessors.