What factor can invalidate the accuracy of a radon test according to building conditions?

The accuracy of a radon test can be compromised by the introduction of outdoor air through temporary venting. When outdoor air is allowed to mix with indoor air, it can dilute the radon levels present in the home, potentially leading to misleadingly low readings. This dilution effect can mask the true radon concentration that would exist without such ventilation, resulting in an inaccurate assessment of the radon risk within the building.

In contrast, other factors listed, such as the winter season, continuous monitoring, and the use of professional testing services, do not inherently invalidate the accuracy of a radon test. For instance, winter conditions can actually influence radon levels due to differences in air pressure and thermal dynamics, but they do not necessarily render the test inaccurate if conducted properly. Continuous monitoring provides a more consistent and thorough understanding of radon levels over time rather than a single measurement, which can also enhance accuracy. Utilizing professional testing services is aimed at ensuring that the testing procedure adheres to established protocols, thereby supporting the validity of the results rather than compromising them.