During the winter months, ventilation is usually reduced since windows are kept closed. This allows radon gas to build up. It also allows radon gas to penetrate to the upper floors of houses and apartment buildings since hot air rises. Radon levels are however, rarely high enough to cause concern above the second floor of buildings. If you have tested your home and found you had a radon problem, also test your water - especially if it comes from a well.
Most radon enters the home through soil, but it can also come through well water.
Most water that enters the home via public water supplies does not contain problematic levels of radon. If you suspect a problem, call your public water supplier. As you shower or use water for other household uses, you can breathe in radon gas. Research suggests that swallowing water with high radon levels can pose risks, too, but these risks are believed to be much lower than those from breathing air containing radon. Radon problems in water can be readily fixed.