At least 12 people have died in domestic gas explosions in the past five years in Great Britain and 178 more have been injured amid concern at the risk posed by corroding service pipes, some laid at the time of the second world war.
It will take time to determine the cause of the fatal blast in Birmingham that obliterated a semi-detached house. But leaking gas from the service pipes that carry gas the last few yards to our homes has been established as the cause of some other explosions that have killed, injured and reduced homes to rubble.
These narrow steel service pipes have often been buried for decades underneath pathways and gardens and, despite galvanisation, can corrode, allowing gas to escape into the earth. It then finds its way into pockets beneath houses and in wall cavities, creating chambers of explosive fuel ready to be ignited by something as small as the spark from a light switch or a fridge thermostat.
Pipe corrosion can be accelerated by acidic soil or rotting vegetation and homeowners often have no idea there is a problem until they smell gas, by which point it can be too late.
Chris Clarke, a partner at Fire Investigations UK, said gas explosions easily topple walls that are designed to be strong in vertical compression but not to resist powerful lateral forces.
Since 1974 a replacement programme for iron gas mains has been under way, including 8m to 10m service pipes that branch off the mains. In 2014 the Health and Safety Executive (HSE) concluded “the management of risk from steel service pipes is currently a significant issue of the gas distribution networks”.
Explosions and fires caused by gas leaks rose from 28 in 2017 to 41 in 2020 and 178 people were injured in the last five years from flammable gas blasts, according to figures from the HSE. They are not always caused by defective service pipes.
Clarke has attended domestic blasts where residents had been trying 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. Corroding aerosol cans left at the back of cupboards can also leak, creating an explosive mix.
“I have been to numerous places where they have blown the walls apart,” Clarke said.
In April, the high court examined an explosion at the Sunderland home of Susan Shepherd, 44, who was hospitalised for a month with extensive burns. When she opened her fridge 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 that ran a metre below her garden. It appears the gas spread into the house’s cavity walls via a redundant clay drainage pipe close to the leak. Shepherd now suffers post-traumatic stress disorder.
The steel pipes serving the neighbouring homes were replaced with plastic a few years earlier – in one case when a new meter was installed, another when a leak was detected. The pipe 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 prioritised mains replacement, and had taken “reasonable care to guard against gas explosions and consequent injury”.
Faults with appliance and copper gas pipework inside homes also cause explosions. The number of dangerous gas fittings identified by engineers increased 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 increasing vigilance amid tighter regulations on gas fitting, which requires Gas Safe-registered technicians