Luke McArdle, the director of McArdles Cleaning and Restoration, said the increasing use of the drug, by smokers and people making it in illicit laboratories in residential houses, posed health concerns for innocent future tenants of the properties and legal liability concerns for the owners of the houses.

"We have probably had two or three [houses] with positive test results," he said.

Two Orange houses had been tested for residue chemicals from illegal drug use in the past three months and one of them needed to be cleaned, he said.

He said they had tested a house for sale on the outskirts of Orange this year for meth contamination at the request of a potential buyer of the property and it had tested negative.

Mr McArdle said the contamination is spread through the houses through vapours that become airborne and liquids which get absorbed into porous materials including ceilings, walls, carpets, furnishings, drains or ducting systems.

He said the contamination from high levels of drug use could result in chronic and acute health effects ranging from nausea to causing brain, liver, heart, kidney and lung damage, and even death.

"It is such a bad drug," he said.

Mr McArdle said, in some cases, the remediation of a contaminated house involved having to remove walls back to bare studs and remove air-conditioning ducting.

The procedure, he said, could cost at least $30,000.

He said if the chemicals had been disposed of down toilets or drains, there would be wider contamination outside the house.

Mr McArdle said while meth-use risks had previously been a problem in Sydney and major cities, the increased use of the drug was now posing threats in regional areas.

The Western Australia Government is considering mandatory testing for methamphetamine contamination in rental properties, which would be an Australian first, according to the Real Estate Institute of Australia.

There are no such moves in NSW at the moment, however.

DECONTAMINATION of a meth-infected house starts with a simple detection test, but it can become very involved if there's a positive finding.

Luke McArdle, the director of McArdles Cleaning and Restoration, said the initial 'yes or no' test cost $600 to $1000.

He said staff examined a small area of a wall, often only 100 square millimetres.

Mr McArdle said traces could often be found in walls and particularly around ceiling air vents and ducting for air-conditioning.

He said it could be spread throughout a house even from the drug user touching door knobs and electrical switches.

Mr McArdle said if a meth laboratory had been in the house, the testing costs would rise to $1500 to $2000 depending on the contamination.

But getting rid of the contamination can blow out to at least $30,000 if walls have to be removed back to the bare studs.

After being cleaned with a peroxide foam, detergents and water, they then need to be replaced and repainted.

He said any porous material, including lights, carpets and curtains, could soak in the drug's vapours and they might need to be removed in the cleaning process.

Decontamination can also involve the removal of all the ceiling insulation and vacuuming the entire ceiling cavity.

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Timbers might also need to be treated with weak acids.

Mr McArdle said pipes needed to be flushed, the property had to be well-ventilated and houses needed to be steam-cleaned or high-pressure cleaned.

Workers need to wear protective equipment including gloves, coverall clothing, booties over work boots and respirators with protective eyewear.