Four fire engines and around 25 firefighters were called to a fire at a flat above a shop on Station Road in Hanwell.
A small part of the entrance of the first floor flat in the three-storey building was damaged by fire.
Two adults and two children were led to safety by crews wearing breathing apparatus. A woman in the flat woke up in the night and noticed the fire. She alerted her family and called the Brigade, asking for guidance on how to leave the property, as the fire was in the hallway blocking them from exiting the flat.
London Ambulance Service treated the four residents at the scene for shock and smoke inhalation.
The Brigade's Fire Investigators believe the fire was caused by a faulty battery charging pack for electric bikes. There were no working smoke alarms in the property.
A Brigade spokesperson said: ”Fortunately, the woman woke up and realised there was a fire, alerted her family and called 999. If she hadn’t woken up when she did, this fire could have had a very different outcome. You should never remove smoke alarms or take out their batteries and they should be tested regularly to make sure they are working.
“This fire highlights just how important it is to have working smoke alarms in your property. Having a smoke alarm in your property can end up saving your life.
“Make sure the entrance to your property is clear from any obstacles which may prevent you from escaping in case of fire.
“Also, ensure your battery charging packs are genuine and suitable for bikes and the devices you are using.”
The Brigade was called at 0440 and the fire was under control by 0514. Fire crews from Ealing, Southall and Heston fire stations were at the scene.