Michelle Ross, 37, woke up shortly after the blaze broke out in an electrical cupboard at the house in Harburn Avenue in Deans, Livingston, at around 2:30am last Saturday.

Lothian and Borders Fire and Rescue Services sayFire officers said the blaze was started by an overloaded mainsplug socket – a common cause of house fires – and that the smoke alarm was faulty.

A spokeswoman added: "It's fair to say that The family were extremely lucky as the effects of smoke inhalation can be fatal quite rapidly."

Ms Ross's youngest daughter, who is 12 weeks old and suffered from bronchiolitis shortly after birth, was rushed to St John's Hospital as a precaution after smoke filled the house, while tests on Ms Ross showed carbon monoxide levels were high.

Her two-year-old daughter and one-year-old son were also in the house at the time of the fire, while. Her older daughter was staying with a friend.

The full-time mum, who is separated from her partner, said it was a mystery how she woke up but she is counting her blessings that her family are safe.

"I don't even know what woke me up," she said. "I just grabbed my three children out of their bedrooms, wrapped them in blankets, and got them out of the house through the back door because the fire was right at the front door.

"Even now I don't know how I managed it. It's the scariest thing that has ever happened to me. One of the firemen said that someone out there must have been watching over me because people don't usually wake up.

"I think it must have been maternal instincts. For some reason the house just didn't smell right and I've been told it was toxic smoke rather than black smoke.

"There is a lot of smoke damage in the house, but that's nothing. The only thing that matters is that my children are safe."

Four firefighters wearing breathing apparatus extinguished the blaze and installed new smoke detectors in the house.

Group manager Andy Girrity has issued advice to householders on fire safety.

"It's extremely fortunate that the occupier was alerted by the smell of smoke. Often People can be overcome by fumes before they have a chance to react.

"Fortunately, in this instance the family suffered no ill-effects, but taking the time to protect yourself from the risk of fire can make all the difference to your family's safety.

"When firefighters arrived at the address the house was filled with smoke. We believe the householder woke up because of the smell of smoke.

"Although there was a smoke alarm, it was not working. The initial cause is thought to have been due to the overloading of electrics. Although the fire turned out to be relatively small there was significant smoke-logging.

"We are keen to remind people to check their smoke alarm regularly. A working smoke alarm can save lives."

Anyone living in the Lothians can contact the fire service for a free home safety visit to fit a smoke detector and give advice on fire hazards such as overloaded sockets.

Six hours earlier, a 30-year-old man was taken to hospital suffering from smoke inhalation in another fire in Blackburn.

Fire crews were called to Mosside Terrace at around 8.25pm to find a garden hut alight. The man was taken to St John's Hospital.