Mould is not only ugly to look at, it poses a serious health risk.

As summer takes hold and humidity rises, mould spores spread rapidly and it doesn't take long for the problem to get out of control.

Birgit Stewart has rented her Sydney home for the past ten years and two years ago her health started to rapidly deteriorate.

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She says it was from the infestation of mould growing inside the home.

“I get chronic lung pains. They put me on Metatrexalate about six weeks ago. I had another episode where my toe went numb. I have been having respiratory problems for years," Birgit said.

“You can see it is just black toxic mould creeping closer and closer into the middle of the room.

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All these marks here are likely to be caused from mould and as you can see it is all over the place.”

Frustrated, sick and with no help from her real estate agent, Birgit contracted an external mould and environmental scientist to evaluate the property. The results revealed the house is categorised as a level four contamination.

Level one refers to a normal or good environment while level four indicates the highest amount of contamination.

At that level, 25 square metres of a home are colonised with mould.

Dr Heiki Neumeister-Kemp is from mould-testing laboratory Mycoloiga. She says mould becomes hazardous when the small spores that are released into the air are inhaled. They can latch on to the lung making breathing difficult and painful.

"We find mould in houses when we have a type or shape of moisture. It can be as simple as condensation, or you let your bath tub overflow," Dr Neumeister-Kemp said.

Claire and Alistair Fremantle are tenants who also lost their home and possessions to mould.

“We didn't notice it was there until I was cleaning for our six-week house inspection. I cleaned a lot of the mould off and I showed it to the agent, and from there it just got worse and worse and worse," Claire said.

“We're living out of a suitcase, we've got our two young kids and we've got a few items of clothing between us and a few toiletry items, that's all we were able to take with us.”

After their children started to suffer from bronchitis, testing revealed that 40 per cent of their bedroom was covered in mould, including their pillowcases.

“I remember touching their blankets and they would be damp during the night because the humidity was so high, so they were breathing in that moist, mouldy air all night long for weeks until I realised,' Claire said.

Don Jones the acting commissioner of NSW Fair Trading says tenants can complain if they feel they are being hardly done by.

"Tenants should expect to have the property they're renting in the standard that they first walked through the door," Mr Jones said.

"If you don't think you are getting anywhere with your landlord you should talk to the consumer affairs agency and see what we can do for you , there are tenancy advisory services in most states," Mr Jones said.

Claire and her family managed get out of their 12-month lease and Birgit plans to take the Real Estate Agent to the tribunal.

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