The Radon fan is vented at ground level. The gas (now highly concentrated as it leaves the exhaust pipe) is below any openings on the house as well as any people who are outside.
It can now reenter the house at a much higher level then what it tested at before the system was installed.
Code requires the venting to be a minimum of 10′ off the ground and 2 feet above any openings within 10′.
Simple code to follow for a licensed contractor who should be properly trained (whose been in business over 15 years).
Be careful what you pay for.