When are condition checks for passive tests conducted?

Condition checks for passive tests are conducted at both the beginning and the end of each test to ensure that the testing conditions are suitable and that the results obtained are reliable. Conducting checks at the start allows technicians to confirm that the testing environment meets specific criteria required for accurate radon measurements, such as stable indoor air conditions, the placement of the testing device, and that no unnecessary disturbances will occur during the testing period.

Performing checks at the end of the test is equally important to verify that the conditions have remained consistent throughout the testing duration and that no external factors may have influenced the results. This thorough approach enables technicians to validate the integrity of the data collected, ensuring that the radon levels measured accurately reflect the indoor air quality during the testing period.

The other options suggest limited or random checks that do not provide the same level of assurance in data reliability, which is why they are not appropriate in this context.