Where does InterNACHI suggest placing testing devices for initial measurements?

The recommended placement for initial radon testing devices is at the lowest lived-in level of the home. This location is significant because radon typically accumulates in lower levels of a building, especially in areas like basements or ground floors. Since radon is a naturally occurring gas that seeps into homes from the ground beneath, testing on the lowest lived-in level provides the most accurate measurement of the radon concentration that occupants might be exposed to.

It's important to recognize that placing devices on higher levels or near windows may not provide a true representation of the radon levels experienced in the home. Higher levels of the home are less likely to have significant concentrations of radon, and testing near windows could introduce outside air and influence readings, making them unreliable. Placing devices at the main entrance could also skew results, as it may not reflect typical indoor air quality throughout the living space. Thus, positioning the testing devices on the lowest lived-in level is the most effective method to ensure reliable and relevant radon measurement results.