If there are no doors or windows in the testing area, where should the measurement not be taken in relation to the exterior wall?

In radon measurement, the guidelines suggest that measurements should be taken at a distance from the exterior walls to avoid the influence of outdoor air infiltration, which can lead to inaccurate readings. The choice to take measurements at least 1 foot away from the exterior wall is crucial because at this distance, the measurement is less likely to be affected by factors such as outdoor ventilation, drafts, and temperature variations that are often found near walls and windows. This creates a more stable environment for testing, allowing for a more accurate representation of radon levels in the indoor air.

Taking measurements closer than this, such as immediately adjacent to the wall, may result in readings that do not accurately reflect the air quality of the overall testing area, as they could still be subject to the influence of outside air, especially in poorly sealed or ventilated structures. Thus, the specified distance of 1 foot helps ensure that the radon measurements reflect the conditions of the room more accurately.