radon in old rowhouses 5

https://radonlevelsyorkpafinder.unionquill.com/posts/understanding-radon-levels-in-york-pa-a-homeowner-s-guide-to-testing-and-mitigation

In many old rowhouses, radon gas can quietly seep up from the ground through cracks in basements or foundations, building up to concerning levels without anyone noticing. With shared walls and aging infrastructure, these homes often lack proper sealing or ventilation, making radon testing a smart step for anyone living in tightly packed urban blocks.