A technical breach at the Corrib Gas processing plant in north Mayo has led to odourless gas circulating on supply lines to homes and businesses in the west.

Gas Networks Ireland has advised customers across counties Mayo and Galway to turn off supply at the meter until further notice.

Gas from the Corrib field is usually piped ashore, refined at the Bellanaboy terminal and dispatched onto the national gas network. 

However, a technical failure at the Shell refinery has led to the gas entering the supply chain, without an odour being added. With no smell, it is impossible to detect a leak. 

For this reason, Gas Networks Ireland said customers in Galway city, Tuam, Headford, Ballinrobe, Claremorris, Castlebar, Westport, Crossmolina and Ballina should turn off their supply at the valve in their meter box until further notice. 

GNI said the decision to issue the turn-off notice followed extensive analysis after Shell informed it about odourless gas.

Gas is odourless but has a smell added to aid with detection.

It is understood the volume of odourless gas released into the network from the Corrib refinery is around 20% of the daily total gas volume supplied by Gas Networks Ireland.

Efforts are being made to remove the unscented gas from the network. This could take up to 72 hours.

The odourless gas is being piped back to the Corrib Gas Terminal where it is being burned off in a series of protracted flaring exercises.

Shell says this is a standard safety mechanism but some locals around the site are critical about the lack of notification they received about the process.

Shell has confirmed that flaring will continue through the night at Bellanaboy, with GNI saying it could take three days to burn off the odourless gas.