The gas is mercaptan, added to natural gas to give it a smell.

BBC: Foul smell complaints in southern England after gas leak

The smell has been identified as that of mercaptan, the chemical added to natural gas to give it an odour.

BBC: French foul smell reaches Bedfordshire and Hertfordshire

The substance responsible is mercaptan - a harmless additive to natural gas.

BBC: How 'Le Pong' engulfed Kent and Sussex

However, if your job involves the more delicate scents of lavender, ylang ylang and neroli, then the stench of mercaptan is more jarring.

BBC: How 'Le Pong' engulfed Kent and Sussex