Shocking sight that greeted a Sunshine Coast family when they looked inside their car after returning from an overseas trip - and it could be very costly

An Australian family got a terrible, unexpected and potentially very expensive shock in their garage when they returned from a recent overseas trip.

They found their car infested with mould spreading across the interior, including the seats, steering wheel, console, floors and doors.

With little of their vehicle spared, the Sunshine Coast mum who posted pictures of the car on Facebook where she asked for advice, was understating the damage when she wrote 'it's so bad'.

She got a lot of advice from people who'd had similar unwanted experiences, with some delivering the very bad news that they didn't think the car could be saved.

'That's a huge write-off,' one wrote, while another added: 'Even if you managed to get that clean, I still don't think I would be able to trust that it is safe.'

Others said that when the same thing happened to their car, the insurance company had written off the vehicle.

Mould removal expert Anthony Johnson from Green Mould Solutions said given the right conditions, a car can be a perfect breeding ground for mould to spread quickly.

'This happens a lot to people, and they get a huge shock when they see it,' he told Yahoo news.

He said if a car has a slightly opened window, it could let a tiny amount of water into the interior. 

The temperature inside can then create humidity, which causes mould to grow and spread quickly.

Once it gets into the fabric and leather interiors it can be hard to get under control.

Mr Johnson said it can take as little as 48 hours for a car interior to be completely taken over by mould. 

While it can be removed, it needs someone with the right equipment to do it. 

'A professional must be called in to use the correct cleaning solution across the different car surfaces, which will kill the mould entirely,' he said.

'You can use a machine to clear the mould in the air, but the key is treating the mould on the surface. Otherwise, it can easily grow back and begin to spread again.'

The specialist said mould is a common problem people in homes, cars, and workplaces and that spores should be treated carefully to ensure their safe removal.

Mr Johnson said it's vital to get a professional who knows how to deal with it 'because it is people's health that can be at risk'.

A lot of mould spores can only be seen with specialised equipment, he said.

Keeping an environment clean, dry and well-ventilated is the best way to prevent mould, Mr Johnson added.