Welding sparks set rooftop foam insulation ablaze, and four workers escaped down a single ladder

The four men, subcontractors working for C Watkins Plumbing Limited, were fitting an air source heat pump atop the Old Telephone Exchange scheme in 2024, according to Britain's Health and Safety Executive (HSE). Sparks from the welding landed on uncovered rigid foam boards laid across the roof. The fire spread over the whole roof and kept burning until the foam was used up. An HSE inspector who happened to be nearby photographed the block on fire.

The roof had one way out: an opening in the floor and a ladder down to Level 14. There were no fire extinguishers on the roof and no way to sound an alarm, HSE said. Inspector Stephanie Hickford-Smith said the men were lucky, and that a fire starting closer to their exit could have ended very differently.

HSE found the company never assessed the risks, wrote no method statement and issued no permit to work for the welding, although its own policies required them. The Ramsgate, Kent, firm pleaded guilty to breaching Regulation 15(2) of CDM 2015, Britain's construction design and management rules, and was sentenced at Staines Magistrates' Court on Oct. 29. HSE guidance HSG168 calls for risk assessments that flag work where fire can spread fast and evacuation is complicated.

U.S. rules cover the same ground. OSHA's construction standard, 29 CFR 1926.352, requires extinguishers or other firefighting equipment ready at the work area, and a dedicated fire watch during and after hot work when ordinary precautions fall short. Under NFPA 51B's 2019 edition, a hot work standard Massachusetts wrote into its fire code in 2022, the fire watch lasts at least one hour after work ends, according to fire protection firm Code Red Consultants.