Six fire engines and around 40 firefighters tackled a flat fire on Llanover Road in Wembley.
London Fire Brigade confirmed that half of the first floor and part of the roof of a semi-detached house converted into flats was damaged by the fire.
Five adults suffering from smoke inhalation were taken to hospital by London Ambulance Service crews.
The fire is believed to have been accidental and caused by failure of lithium batteries within a laptop computer.
A London Fire Brigade spokesperson said: “It’s incredibly concerning we are continuing to see a rise in incidents involving lithium batteries.
“Please follow our advice on safe charging and ensure everyone in your home knows what to do in the event of a fire.
“We would suggest people try not to charge them when they are asleep, so that if there is an issue they can react quickly.
“We also 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.”