Radon is a gas that can be found in both indoor and outdoor environments. It is formed when uranium breaks down in the soil, rock and water. Radon can enter homes through cracks in the foundation or other openings. Once inside, it can build up to high levels.
Opening windows does not reduce radon levels indoors. In fact, opening windows may actually increase radon levels because it allows more of the gas to enter the home. The only way to reduce radon levels is to install a ventilation system that removes the gas from the home before it has a chance to build up.