MAH_2019

Protocol for Conducting Measurements of ANSI/AARST MAH 2019 Radon and Radon Decay Products in Homes 9 7.0 ACTIONS BASED ON TEST RESULTS 7.1 Action Level Guidance Countries worldwide have adopted Action Levels for radon exposures. Most are similar to the 4 pCi/L (150 Bq/m 3 ) action level recommended in the United States. The action level observed should comply with the guidance of the country, state or other local jurisdiction of authority where the test is being conducted. U.S. Action Level. The following Action Level descriptions reflect guidance from the United States Environmental Protection Agency (EPA): • 4 pCi/L or greater ( ≥ 150 Bq/m 3 ) Fix the home. The higher the radon concentration, the more quickly action should be taken to reduce the concentrations. • Below 4 pCi/L (< 150 Bq/m 3 ) Consider fixing the building if test results indicate that radon concentrations are greater than half the action level , such as between 2 and 4 pCi/L (75 and 150 Bq/m 3 ) Because the hazards from radon are virtually the same for radon concentrations that are near action level thresholds, the World Health Organization recommends limiting long-term exposures to less than 2.7 pCi/L (100 Bq/m 3 ). When measurement devices indicate concentrations lower than about 2.0 pCi/L (75 Bq/m 3 ), test data should normally be interpreted as being lower than the test device can accurately measure. 7.2 When Two Test Results Disagree 7.2.1 Acceptable When two test devices were deployed to test the same testing location, the average of the two test results is to be used for determining needs for mitigation if: a) both test results are above the action level , or b) both test results are below the action level . Note—Some variation between detector results is typical. However, if the variation between collocated (side-by-side) detectors is unusually large, it might indicate problems in the measurement system. Section B of the attached MAH Companion Guidance provides general information and example control limits that guide professional services. 7.2.2 Where test results disagree on exceeding the action level When one test result is above the action level and the other test result is below the action level : a) Acceptable —If the higher result is less than twice the lower result, the average of the test results is to be used to determine if this location needs mitigation . b) Not acceptable —If the higher test result is more than twice the lower test result: 1. For two collocated (side-by-side) tests conducted at the same time, a repeated collocated test for this location is required to obtain a valid measurement. 2. For two tests conducted in the same location but at different times, obtaining confirmation on whether mitigation is warranted requires additional testing.