Chapter 9 Interpretation: 2020 NGBS Radon Testing

Published Friday, August 29, 2025

Question

If a building in Radon Zone 1 installs an active radon system, is it exempt from radon testing?

Interpretation

2020 NGBS Section 902.3.2 requires radon testing for buildings located in EPA-designated Radon Zone 1. If testing reveals radon concentrations above the EPA action level, 4.0 pCi/L, an active radon mitigation system must be installed. However, the NGBS does not require post-installation re-testing to verify that the mitigation system is effective.

Download the detailed interpretation