Some residents wore white surgical facemasks to avoid inhaling the ash -which in some areas lay 15 cm deep.

Shot on a camera-phone in Yokohama, the video purportedly showed a street-fight triggered by someone jumping a queue to buy surgical facemasks.

Results: Of 30 identified, only 3 laboratory studies of 14 different respirators and 12 surgical facemasks were found.

Surgical facemask: £4.52 for 100 Facebook Twitter Pinterest A woman in a mask during heavy smog in Harbin, northern China.