If your property requires decontamination, the first step is to do a detailed assessment (also called a room-by-room meth test).
This test will give you individual results for every room. It will inform the cleaners (decontaminators) of which rooms are most contaminated and how bad it is. They need this info so they do an effective job cleaning.
Cleaning usually involves removing all carpets and soft furnishings. As well as any ducting and/or heat pumps and heat transfer systems. Strong chemicals are used on all surfaces in contaminated areas including walls, ceilings and inside cupboards and doorways.
Once the cleaning is done. The property will need to be aired usually for 2-3 days. Following that, the areas cleaned will be re-tested to check that the decontamination was successful.
If it was successful, the decontaminators will issue a clearance report and certificate. If not successful, the cleaning / re-testing process will continue until it is successful.