Families escaped a Bayswater building after a fire broke out in the basement of the terraced property.
It happened in the early hours of Friday (April 17) at the property in Linden Gardens.
The property had been converted into 23 self-contained flats and 15 people left the building before fire crews from Kensington, Paddington and North Kensington arrived.
Watch Manager Matt Wintle, who was at the scene, said: “The fire started in a former coal storage area beneath the road that was used as a utility room. The smoke set off an automatic fire alarm that was sounding when firefighters arrived.
“It was the loudest alarm I have heard in all my 12 years in the brigade and did its job well. The residents were alerted to the danger and all of them left safely.”
The brigade was called at 2.41am and had the fire was under control at 3.15am.
The cause of the fire is believed to be accidental.
The property suffered slight damage as a result of the fire and crews said they were not treating the blaze as suspicious.
