Smog in the city.<br/> <br />A dense grey pall shrouds China's capital and many commuters wear masks.<br/> <br />Beijing Residents are no strangers to noxious air pollution. But it seems that there are limits.<br/> <br />Beijing has issued a yellow alert -- the second most serious of four...It's the first time the Environmental Protection Bureau has used its new colour coded warning system unveiled last October.<br/> <br />Smog levels in China's capital city exceeded dangerous highs of 350 on Thursday.<br/> <br />Air pollution readings measuring the number of unhealthy particles in the air higher than 300 are considered hazardous by the World Health Organisation.<br/> <br />(SOUNDBITE)(Mandarin) 25-YEAR-OLD UNEMPLOYED MAN MR. ZHANG SAYING:<br/> <br />"Beijing's air is now like living in a steamer with all sorts of smoke, haze and smog. We've all become human vacuum cleaners"<br/> <br />The excessive pollution levels are expected to continue for three days and people have been warned to reduce outdoor activities, use public t
