radon gas test

https://theeparadonactionlevelpro.dovetailscope.com/posts/understanding-the-epa-radon-action-level-for-st.-louis-home-sales

A radon gas test is a simple way to check if your home has unsafe levels of this radioactive gas, which comes from soil and can cause lung cancer. You place a small detector in the lowest living area for a few days, then mail it to a lab for analysis. It's a smart, low-cost step for health and peace of mind.