[BEIJING] Wielding an "inspector" badge, volunteer Liu Li follows his nose as he sniffs out violators of China's toughest-ever tobacco control law, enacted a year ago on Wednesday, as Beijing fights to keep its air smoke free.
China has more smokers than any other country, but Liu's efforts partly explain the relative success of the capital's ban on smoking in public spaces.
"We're very sensitive. We can tell from a single whiff if someone's been smoking," said the bearded art professor, patrolling a downtown office building.
Prof Liu, 33, moonlights as a leader of blue-vested volunteers who pursue violators and even extract letters of confession from smokers to be passed on to authorities.
"Keep your footsteps quiet," he whispered to his squad of two, pausing cautiously outside a stairwell. "Sometimes when people hear us coming, they try to run".
China has the world's largest smoking population, with 28 per cent of adults and half of its adult men estimated to regularly use cigarettes.
The World Health Organisation (WHO) says a million people in the country die of tobacco-related illnesses annually, with second-hand smoke contributing to some 100,000 deaths each year.
Beijing's law enacted last June makes smoking in public locations such as offices, restaurants, hotels and hospitals punishable by fines.
Businesses that fail to snuff out smoking can be forced to pay up to 10,000 yuan (S$2,090), while smokers themselves can be penalised 200 yuan. Tobacco advertisements are not allowed to appear outdoors.
China's law enforcement is often weak and at the time many were sceptical, but experts say that despite imperfect enforcement, the law has been largely effective.
WHO China representative Bernhard Schwartlander told AFP he was "very happy" with the law, adding implementation had "in many ways exceeded our expectations".
According to official figures, Beijing raised more than 1 million yuan in smoking fines since last year.
The Beijing Health and Family Planning Commission says just four per cent of public places see regular smoking, down from more than 12 per cent a year earlier.
The success is partly due to 12,000 "anti-smoking campaign volunteers" - from primary school students to pensioners - registered in Beijing.
They appear in parks, restaurants and workplaces, ask people to stub out at bus stops, and inspect office buildings in top-to-bottom sweeps.
Nearly 70,000 facilities were inspected last year, officials said.
Though volunteers have no power to issue fines, Prof Liu said most people "are willing to listen to us if we take the right tone, when they see us wearing our uniforms and certificates".
The aim is to "patiently dissuade people," he explained, admitting: "A few can't really change their thinking and might get a bit violent in their language".
Enforcement can be shaky in a municipality with more than 20 million residents, with smoking in numerous establishments still tolerated.
Coffee shop manager Wang Haiguang told AFP "there has been a decrease in smoking here this year." But it is difficult to confront customers, he added, as two men nearby dragged on cigarettes.
"They say, I'll just smoke one and then I'll go. Since they are clients of ours, we sometimes have to respect their opinions," he said.
Health activists have called for similar measures to be imposed elsewhere in the country, and a national law has been drafted.
Mr Schwartlander called Beijing's efforts "very solid" proof that such measures could be extended, but said the draft is riven with "problematic loopholes" such as allowing smoking in individual offices.
"A weak national smoke-free law would... fail to protect China's people to second-hand smoke at a very great cost to individuals and the economy," he said.
One explanation for a weaker national law is the continued clout of China's state-run tobacco industry, which provides the government with colossal revenues: 911 billion yuan in taxes and profits in 2014.
China's tobacco regulator shares offices and senior officials with the state-owned China National Tobacco Corp - a near-monopoly and by far the world's biggest cigarette producer.
Beijing Anti-Tobacco Association Leader Zhang Jianshu said the ban could be harder to enforce in other regions.
"Beijing is the capital - people's levels of civility are comparatively higher here, with most a bit better about following rules".