To effectively reduce and maintain radon levels below 4 pCi/L, what vacuum is typically required beneath a slab?

The choice that indicates a vacuum of 0.003 to 0.020 inches of water column is typically considered effective for reducing and maintaining radon levels below 4 pCi/L. This range of vacuum is significant because it ensures that the soil gases, including radon, are effectively drawn from beneath the slab and vented outside, where they can disperse.

Maintaining this level of vacuum is crucial for creating a barrier that prevents radon from entering the living space. It's a balance; too little vacuum may not sufficiently mitigate radon intrusion, while too much could induce other issues such as soil instability or the potential for unhealthy air quality from other gases.

The selected vacuum range has been recognized in radon mitigation guidelines as being effective in creating a reliable pressure differential that helps manage and reduce radon levels within structures. Understanding the mechanics behind this vacuum and its application in radon systems is vital for anyone involved in radon mitigation.