January 22, 2013

expert reaction to French gas leak

An accidental release of mercaptan gas, the pungent chemical added to odourless municipal gas, from a factory in the French town of Rouen drifted over the British Channel into south east England.

Tony Ennis, Technical Director at Haztech Consultants Ltd, said:

“The material released is that which is used to give the distinctive odour to natural gas. It is added in extremely small quantities and is detectable by smell at tiny concentrations – in the order of 1 part in 2.8 billion.  It is used because it has such a distinctive smell and because it can be used in such small quantities that it does not affect the combustion properties of the gas itself.  It is not toxic at low concentrations despite the strong smell!

“The material is one of a group known as Mercaptans – many of which are extremely smelly. Mercaptans contain sulphur and hydrogen sulphide is released from rotten eggs, hence the smell being likened to rotten eggs.

“Natural gas itself (mainly composed of methane) has no smell and the odour is added to make people aware of any gas leakage as a safety measure.

“The stable weather conditions (little atmospheric turbulence) and low temperatures at the moment, coupled with the low threshold of detection of this material mean that the smell is drifting across the UK, a distance of over 200 miles from the source.”