The native Chaoyang resident has been sweeping streets for nearly a decade and he notices that Beijing's smoggy days happen more often than in the past. But Yang, who is just over 50, says he's never had his health checked because he can't afford a doctor's visit. Nor has he been told that the high level of fine particles in the air can significantly increase the risk of heart disease, a warning given by the World Health Organisation.

His protective gear includes a face mask, but he rarely dons it, finding it difficult to inhale through the thick cotton.

"Nobody wants to breathe bad air, but what can I do? I can't quit," he says. "The job pays only about 3,000 yuan a month, but it is a government job. It is stable."

China's capital was hit by some of the worst air pollution on record last winter. Sooty skies plague not only Beijing, but many areas in northern China. There, decades of reliance on coal burning for heat has lowered life expectancy. International researchers found that people in northern China live an average of 5.5 fewer years than residents in the south, according to a study released in July. Last month, after firing up the heating systems in Harbin , the air grew so dense and dirty that schools were closed on October 21.

The Chinese government has launched many measures, such as shutting down small polluting factories, restricting the number of cars on the road and banning outdoor barbecues in downtown areas, but it appears the measures have been in vain.

The central government has tried to induce several regions, including Beijing, to lower pollution levels, even awarding five billion yuan to the city and its surrounding region to cut particulate levels by 25 per cent.

City residents fear that whatever is in the air could be worse this year. Smoggy days started in October, the "golden month" usually known for its blue skies and fresh air. Air pollution has become such an international embarrassment that the Beijing government has introduced strict measures to tackle its acrid skies, including imposing mandatory factory and school closures. Last month the city said it would restrict drivers to using their cars every other day during periods of heavy pollution.

But the city isn't above casting blame. The government has argued that the most significant pollution comes from neighbouring provinces and cities, mostly from vehicle and coal-burning emissions.

Trapped under gritty skies, Beijing's denizens respond in many ways. Foreigners and the wealthy don high-tech face masks and install costly home air purifiers. They travel in cars equipped with fine particle removal systems, or leave for resorts on Hainan Island where the breeze is clean. One Beijing-based artist, Matt Hope, created a bicycle that uses peddle power to generate electricity for an air filtration system. But most everyone else muddles through. Like residents of Los Angeles in the smoggy 1970s and Londoners of the inky industrial 1800s, Beijingers try to make small changes in their daily routines to protect themselves as best they can.

Jane Ji, a 31-year-old expectant mother and communication engineer, considered becoming one of the "migratory birds" last winter when heavy pollution hit the capital, closing roads and grounding flights for days.

But she has nowhere to go.

"It looks like there is smog in places where we are able to find good jobs," says Ji. "And you can't find a good job in those environmentally-friendly places, like Zhoushan (in Zhejiang ) and Bama (in Guangxi )."

Ji moved from Shenyang to Beijing in 2008, shortly before the Beijing Olympics, when the Chinese government introduced strict measures to limit pollution and improve air quality.

"Beautiful sunshine, blue sky and fewer cars on the roads," she recalls seeing then. "Actually I felt nothing then, just like a healthy man would never know what sickness is" if he'd never experienced it.

Every day before heading to work she checks the air quality from an app on her iPhone. There she checks readings from the US embassy of fine air particles with a diameter of 2.5 micrometres or less. It's the material found in smoke and haze that belches from power plants and cars.

Ji says she knew nothing about particulate matter until three years ago when a Canadian colleague worriedly showed her the readings on his iPhone. The data helps her plan her day, choosing how much time to spend outdoors and what form of transport she'll take to work.

Ji lives with her husband near Wangjing , a major residential and commercial area in northeast Beijing. When the fine particle concentration exceeds 100 micrograms per cubic meter - four times the level deemed safe by the WHO - she takes buses to work instead of walking.

On those days, she turns on a new HP air purifier at home. Then she dons a US-made "I Can Breathe!" mask. Recommended by her foreign colleagues, she bought it online two months ago for more than 200 yuan (HK$253) - much more expensive than the Chinese brands. "I hope it's working, and it should be working because the US national cyclists wore these masks during the Beijing Olympics," Ji says.

After becoming pregnant, Ji became increasingly sensitive about smog health risks. "I would clean my face, nose and mouth after work, keep windows closed and avoid unnecessary outdoor activities when smog hit, although doctors suggest pregnant women take a one-hour walk every day," she says.

Although the city government advises the young, elderly and ill to avoid outdoor activities, not everyone is willing to make that sacrifice.

For Li Huaizhong, a former aerospace engineer, brisk walking has been a big part of his retirement. Like other local residents who believe exercise can fortify their health, Li sets out each morning near his home in the north of Beijing.

Li is very proud of his health. Free of cardiovascular disease at age 80, he often outpaces other walkers and finishes a fourkilometre course in 40 minutes. Like the mail carriers in America, Li says his exercise "could be stopped neither by wind nor rain".

When smog hits, Li sometimes must compromise. He shortened his route to one kilometre in mid-October when the city was blanketed by smog for several consecutive days. But he stops short of donning masks and relying on air purifiers.

"I don't know how effective [a mask and air purifier] can be," says Li. His theory is simple: "If you keep yourself indoors when smog hits, you can never go out in Beijing."

While pollution seems to crimp most activities, it has oddly been a boon to some forms of leisure. Kou Wen, a senior engineer with Beijing Planetarium, says the size of the city's stargazing community has grown in recent years, despite the smog.

In Haidian district alone, more than 50 primary and middle schools have or will soon establish amateur astronomy programmes. Crowds with telescopes have gathered at popular stargazing sites in suburban areas such as Yanqing on clear nights. The reason is a bit ironic, Kou says. The rapid rise in car ownership has contributed greatly to air pollution, and the situation is particularly bad on days with severe traffic jams, which are increasing in Beijing. But cars, Kou argues, also extend the reach of amateur astronomers.

"For a sharp image of distant stars and galaxies we need to get away from the city as far as possible. Smog is one reason, but our biggest concern is light, which never leaves," he says. "In the past it was quite troublesome to organise a trip for observing due to the dependence on public transportation such as buses and trains. Now every family has a car. We can make a round trip to Inner Mongolia in a weekend."

To rid the city of smog and city light completely, the planetarium is building a large telescope in Tibet that would, for the first time, allow amateur astronomers to access and control a powerful astronomical device remotely. Kou would not reveal its cost, but the telescope, 50 centimetres in diameter, is large enough to peek into distant galaxies.

"Rapid economic development has caused the smog that blurs the sky over the city, but it has also enriched people's pockets and allows them to go to places they were unable to reach and see things they were unable to see before," Kou says. "Everyone hates smog, but life moves on."