What must be done with accessible openings and gaps surrounding the hollow void network in a Block Wall Depressurization?

In the context of Block Wall Depressurization, sealing accessible openings and gaps surrounding the hollow void network is critical for effective radon mitigation. These openings can serve as pathways for radon gas to enter a building. If they are not sealed, radon can bypass the mitigation system, undermining its effectiveness and allowing higher levels of radon to accumulate within the structure.

Sealing these gaps is essential to ensure that the depressurization system works efficiently by maintaining the difference in pressure that helps to draw radon gas from beneath the foundation and expel it outside. Proper sealing can also improve energy efficiency by preventing unwanted air infiltration and thermal loss.

Other options, such as enhancing the openings, painting them, or monitoring them regularly, do not address the immediate need to prevent radon entry through these pathways. While monitoring may be a necessary part of an ongoing mitigation plan, it does not directly contribute to the prevention of radon invasion as sealing does. Therefore, sealing accessible openings is the most appropriate practice in this scenario.