Sydney family lucky to be alive after faulty heater leaks carbon monoxide

Three people were left helpless and unable to move after a faulty gas heater leaked carbon monoxide in their Sydney home.

Loui Abouhamad was home with his mother and father - aged in their 70s - last night when they started to feel dizzy, completely unaware they were suffering carbon monoxide poisoning.

"Dad was in bed, he walked out and said he wasn't well then I was literally crawling around on the floor," Abouhamad said.

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Fire crews believe the residents were overcome by carbon monoxide gas emanating from a faulty indoor gas heater.

"I went to the heater straight away, turned it off, tried to open a window and managed to open one but I couldn't get to the others. I couldn't even walk," Abouhamad said.

Abouhamad called triple zero and his neighbour for help.

He and his parents were taken to hospital.

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Firefighters picked up a lethal reading of 169 parts per million on gas detectors. Anything over 30 is considered unsafe.

"Carbon monoxide is a silent killer, you literally sleep to death," Fire and Rescue NSW Superintendent Adam Dewberry said.

"It is so lucky that we're not talking about a triple fatality ... those residents were so sick when firefighters and paramedics arrived."

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Carbon monoxide is a colourless, odourless and tasteless gas that can render a person unconscious and prove deadly if allowed to build up in a confined space.

People using gas heaters in cold weather are urged to make sure their devices are serviced regularly - once every two years - by a qualified gasfitter.

Some gas heaters also need a source of fresh air in order to function properly, so check the safety advice.