may delay or decline a purchase if the seller has not successfully abated radon to less than 4 pCi/L. The accuracy of the residential radon test depends upon whether closed house conditions are maintained. Thus the occupants will be instructed not to open windows, etc., for ventilation during the pendency of test, usually two days or more. However, the occupants, if the present owners, will be motivated to pass the test and insure the sale, so they might be tempted to open a window to get a lower radon score. Moreover, there may be children or immature teens or young adults in the house who will open a window for ventilation notwithstanding instructions not to do so, particularly in uncomfortably hot weather. Accordingly, whether the potential purchaser should trust the result of such a test is problematic. Management of radon service provider certification has evolved since being introduced by the EPA in 1986. In the 1990s this service was "privatized" and the National Environmental Health Association (NEHA) helped transition the voluntary National Radon Proficiency Program (NRPP) to be administered by private firms. , the NRPP is administered by the American Association of Radon Scientists and Technologists (AARST). Some states, such as Maine, require landlords to test their rental properties and turn the results in to the state. In limited cases the landlord or tenants may do the testing themselves. The rules in each state vary. In many cases there are private contractors that will inspect hired by the city. Testing in Canada Health Canada recommends regular annual testing, either by hiring a qualified tester or by using a home-testing kit that should be checked quarterly. Canadian Government, in conjunction with the territories and provinces, developed the guideline to indicate when remedial action should be taken was originally set at 800 Bq/m3 (becquerels per cubic meter) and since reduced to 200 Bq/m3. This new guideline was approved by the Federal Provincial Territorial Radiation Protection Committee in October 2006. Testing in the UK Radon testing in the UK is managed UKradon, a department of Public Health England. Testing in Norway The Norwegian Radiation and Nuclear Safety Authority (DSA) developed the protocol for radon measurements in residential dwellings with respect to rental accommodation, which is governed by The Radiation Protection Regulations. Methods of radon gas mitigation Because high levels of radon have been found in every state of the United States, testing for