At least 12 people have died in household gas explosions in the past five years in Britain and 178 others have been injured amid concerns about the risk posed by corrosion of service lines, some laid at the time of World War II.
It will take time to determine the cause of the deadly explosion in Birmingham that wiped out a semi-detached house. But gas leaks from service lines that carry gas the last few feet to our homes have been established as the cause of other explosions that have killed, injured and reduced homes to rubble.
These narrow steel utility pipes have often been buried for decades under driveways and gardens and, despite galvanizing, 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 there is a problem until they smell gas, in which case it may be too late. .
Chris Clarke, partner at Fire Investigations UK, said gas explosions easily toppled walls designed to be resistant to vertical compression but not to withstand strong lateral forces.
Since 1974, a program to replace iron gas mains has been in progress, including 8 m to 10 m service mains which branch off from the network. In 2014, the Health and Safety Executive (HSE) concluded that “risk management of steel service lines is currently a significant issue in gas distribution networks”.
Explosions and fires caused by gas leaks have risen from 28 in 2017 to 41 in 2020 and 178 people have been injured in the past five years by flammable gas explosions, according to The figures of the HSE. They are not always caused by faulty service lines.
Clarke witnessed household explosions where residents tried to make hash oil, a cannabis derivative created using butane gas as a solvent. The explosive compound can build up in a makeshift laboratory to create a combustible chamber. Corroded spray cans left in the back of cupboards can also leak, creating an explosive mixture.
“I’ve been to many places where they’ve blown up the walls,” Clarke said.
In April the high court considered an explosion at the Sunderland home of Susan Shepherd, 44, who was hospitalized for a month with significant 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 service pipe which ran three feet under his garden. The gas appears to have leaked into the cavity walls of the house via a redundant clay drain pipe near the leak. Shepherd now suffers from post-traumatic stress disorder.
The steel pipes serving neighboring houses had been replaced with plastic a few years earlier – in one case during the installation of a new meter, in another when a leak was detected. The line serving Shepherd’s house had been in situ for 78 years.
The court found that the supplier, Northern Gas Networks, had followed HSE policy, which gave priority to network replacement, and had taken “reasonable precautions to guard against gas explosions and consequent injury”.
Faults in appliances and copper gas lines inside homes also cause explosions. The number of unsafe gas fittings identified by engineers rose from 2,299 in 2017 to 3,292 in 2020, with the majority of the increase in owner-occupied properties rather than rented properties.
However, this may be due to increased vigilance under stricter gas fitting regulations, which requires Gas Safe registered technicians.