At least 12 people have died in gas explosions in the UK in the past five years and 178 others have been injured amid concerns over the risk of corroding utility lines, some of which were laid around the time of the Second World War.
It will take time to determine the cause of the deadly blast in Birmingham that destroyed a semi-detached house. But gas leaks from the supply pipes that carry gas the last few meters to our homes have been identified as the cause of numerous other explosions that have killed, injured and reduced homes to rubble.
These narrow steel supply pipes have often been buried under paths and gardens for decades and, despite being galvanized, can corrode, allowing gas to escape into the ground. It then finds its way into pockets under houses and into wall cavities, creating chambers of explosive fuel ready to be ignited by something as small as the spark from a light switch or refrigerator thermostat.
Pipe corrosion can be accelerated by acidic soil or decaying vegetation, and homeowners often have no idea of a problem until they smell gas, and then it may be too late.
Chris Clarke, a partner at Fire Investigations UK, said gas explosions easily topple walls designed for strong vertical compression but fail to withstand strong lateral forces.
An iron gas mains replacement program has been implemented since 1974, but the 8 m to 10 m long service lines branching off the main have not been covered. The policy mandated by the Health and Safety Board was that only where work was already in progress or there was evidence that adjacent pipes were corroded should the gas company replace them with plastic. It was a known risk. In 2014, the HSE concluded that “the risk management of steel service pipes is currently a major issue in gas distribution networks”.
Explosions and fires caused by gas leaks rose from 28 in 2017 to 41 in 2020, and 178 people have been injured by flammable gas explosions in the past five years, according to figures from the HSE. They are not always caused by defective service pipes.
Clarke has taken part in home explosions where residents attempted to make hash oil, a cannabis derivative made using butane gas as a solvent. The explosive compound can build up in a makeshift lab to create a combustible chamber. Corrosive aerosol cans, often kept in the back of cupboards, can also leak and create an explosive mixture.
“I’ve been to numerous places where they’ve blown the walls apart,” Clarke said.
In April, the Supreme Court investigated an explosion at the Sunderland home of Susan Shepherd, 44, who had been hospitalized for a month with severe burns. When she opened her refrigerator door one morning in August 2017, a gas explosion destroyed her semi-detached house. HSE investigators later discovered a hole in the steel utility pipe that ran a meter below their garden. It appears that the gas spread into the cavity walls of the house via a redundant clay drainpipe near the leak. Shepherd now suffers from post-traumatic stress disorder.
The steel pipes of neighboring houses were replaced with plastics a few years earlier – in one case when a new meter was installed, another when a leak was discovered. The pipe that fed Shepherd’s home had been in situ for 78 years.
The court found that the supplier, Northern Gas Networks, had followed HSE policy which gave priority to replacing the mains and that it “exercised reasonable care to protect against gas explosion and resultant injury”.
Faults in appliances and copper gas pipes in houses also cause explosions. The number of hazardous gas fittings identified by engineers increased from 2,299 to 3,292 from 2017 to 2020, with most of the increase occurring in owner-occupied rather than rented properties.
However, this may be a result of increased vigilance in the face of stricter gas connection regulations requiring Gas Safe registered technicians