Beijing smog 20 times international safe levels
Sellers of face masks in the Chinese capital are running out of stock as Beijing suffers its sixth day of a smog alert.
Pollution readings for dangerous small particles are twenty times higher than the internationally recognised safety limit and even higher in parts of a neighbouring province.
Most leading manufacturers of face masks said they had sold out following a rush of customers seeking to protect their lungs from the choking fumes.
Visibility in Beijing is down to a few hundred metres and residents say the upper floors of many buildings have disappeared in the haze.
BBC Weather's Chris Fawkes spoke to BBC World about the chances for improvement.