In a house with forced air heating & cooling, radon gas can easily be dispersed throughout the entire residence. When radon gas is released through a radon mitigation system above the roofing, the radon concentration falls off dramatically with distance from the factor of discharge. As a matter of fact, the radon gas focus approaches history levels at 3-4 feet from the discharge point. EPA forbade ground degree discharge of radon largely because of the capacity for re-entrainment of the gas into your home and due to the possibility of children being subjected to high radon levels. The concentration of radon gas at the discharge point can be 10s of thousands of picocuries per minute.