Faulty Valve Releases 700kg Of Highly Flammable Gas From Ferry Carrying 82 Passengers

A faulty valve on an LNG-powered ferry named Glen Sannox caused the uncontrolled leak of about 700kg of highly flammable methane in Scotland last year, according to an investigation by the operator, CalMac.

The ferry was carrying 82 passengers when the incident happened on June 3, 2025, while travelling between the Isle of Arran and the mainland. The gas continued to escape for about 12 minutes.

Some of the gas entered a ventilation intake and reached the ship’s generator room, setting off the gas alarms.

The port main engine also shut down automatically while the ferry was heading towards Brodick on Arran.

CalMac described the failure in the ferry’s gas fuel system as “critical”. It said the chance of an explosion was low.

The ferry finished that crossing using diesel fuel. However, methane leaked again during its return trip to Troon in South Ayrshire.

The operator’s investigation found that the crew should not have used gas again before finding out why the alarm had gone off.

Glen Sannox began passenger services in January 2025. It is the first UK-built ferry of its type to use liquefied natural gas (LNG).

The vessel’s propulsion system was designed, supplied and commissioned by Finnish company Wärtsilä, which is known for its LNG engines. The company worked on the project as a subcontractor to Ferguson Marine shipyard.

The amount of methane released during the incident was about 700kg. CalMac said this was enough gas to fill a four-bedroom house.

The incident was not announced publicly at the time. BBC Scotland News obtained details through a freedom of information request and reported them on Wednesday.

Glen Sannox has not used LNG to run its main engines since the incident. The vessel’s methane tank was fully emptied in November 2025.

CalMac said it had taken action after the incident and that lessons had been learned. The operator said the ferry is safe to use LNG.

A CalMac spokeswoman said Glen Sannox had become an important part of the company’s vessel fleet and had been providing services on several routes during 2026.

She said the ferry was not filled with LNG again after its annual overhaul at the start of this year because the company wanted to get the vessel back into service as quickly as possible.

References: BBC, dailyrecord