'We were very lucky. we could have been facing a week-long smog'

Geologist Euan Nisbet analysed how the climate affected the fumes from the Buncefield oil depot fire

The "right" weather after the Buncefield oil depot fire in Hertfordshire may have saved thousands of lives, according to Euan Nisbet, professor of geology at Royal Holloway, University of London.

People living in southern England should be breathing a sigh of relief after the conditions on Sunday prevented acrid fumes becoming trapped at ground level.

"We were very lucky," said Professor Nisbet. "We could have been facing a week-long smog, which would have had a disastrous effect on asthmatics or elderly people with respiratory problems."

If the weather had been calmer and warmer, Professor Nisbet explained, we would be facing a health disaster. "The accident was very serious, but it could have been a very dangerous incident.

"The column of fire was acting almost like a chimney carrying the dense black smoke upwards. The cloud moved sideways when it reached the free troposphere. By this stage, though, it had dispersed and would not have been dangerous - a bit like being behind a smelly truck."

He added that, under different weather conditions, the firefighters would have needed to put the fire out quickly because once the chimney effect was interrupted, the polluted air would have swirled about locally.

Professor Nisbet began his career at Cambridge University and has been at Royal Holloway since 1992. He specialises in Archaean geology and monitoring atmospheric greenhouse gasses.