When using two collocated passive devices for testing, how far apart should they be placed?

Placing collocated passive devices for radon testing at a distance of 4-8 inches apart is important for obtaining accurate and reliable measurements. This spacing allows for a sufficient area of air circulation between the devices, minimizing interference from one device to another. The distance helps ensure that each device captures a similar representation of the radon concentration present in the environment without skewing results due to one device being directly influenced by the other.

If the devices are positioned too close together, such as within 1-2 inches or 2-4 inches, they may affect each other’s readings and complicate data interpretation. On the other hand, placing them further apart, like 10-12 inches, can lead to variations in radon levels across the sampling area, which may not reflect the actual radon concentration accurately. Thus, the recommended distance of 4-8 inches strikes a balance, ensuring representative sampling while reducing the likelihood of interference.