Four fire engines and around 25 firefighters tackled a fire at a mid-terraced house converted into flats on Western Road in Southall.
Part of a flat on the second floor was damaged by fire. Two men left the building before the Brigade arrived and were taken to hospital by London Ambulance Service crews.
A London Fire Brigade spokesperson said: “Smoke alarms fitted in the property alerted two residents in the rear garden, who then saw a fully developed fire in the house. This incident shows the importance of having smoke alarms in your home.
“They give the earliest possible warning of fire and you should have working smoke alarms in every room where a fire can start, plus a heat alarm in the kitchen. They should be tested regularly.
“Firefighters recommend that you have a look at our online Home Fire Safety Checker to make sure there are no hidden hazards in your home.
“The online tool will ask you a series of questions that will help us work out the level of risk in your home, or the home of someone you care for. It only takes a few minutes to get tailored advice to keep yourself and loved ones safe from fire.”
The Brigade was called at 2200 and the fire was under control by 2259. Fire crews from Hayes, Southall, Chiswick and Heathrow fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.