Turvey Park firefighters believe the fire was caused by a faulty heater that the residents had salvaged last week.

The Appliance Man electrician Adam Oliver said old and discarded heaters were often filled with dust and moisture, which drastically increased the chance of an electrical fire.

"If something is picked up off the side of the road, it's something I wouldn't be plugging in. It's on the side of the road for a reason," Mr Oliver said.

"It's a good reminder to let people know that it pays to get the electrical appliances tested - that'll give you the peace of mind and the reassurance that nothing's going to happen. We get a lot of people throughout the years that like to fix things themselves, which is a bit scary."

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Turvey Park Fire and Rescue NSW firefighter Ben Dowling urged residents not to try to fix faulty electrical appliances themselves, saying it often ended in electrical short circuiting and house fires.

"If you do have a faulty piece of electrical equipment it must be repaired by a licensed electrical contractor - don't do it yourself. It's just too risky," Mr Dowling said.

"It's important you only use equipment that's been tagged by a professional tester or purchased new from the retail store or manufacturer."

He said the risks were even greater for those who live in older houses, which sometimes did not come with residual current activator switches that prevents short circuiting. Residents can get safety switches installed for peace of mind.

Anything above 240 volts, whether it be a heater, air conditioner, or smoke alarm, needs to be installed by a properly licensed contractor.

Mr Dowling is also reminding residents to check their smoke alarm batteries especially during the winter months, which are one of the most dangerous periods for house fires.

"We are always pushing for working smoking alarms in winter time at every opportunity, because it really does save lives," Mr Dowling said.