There are several methods that a contractor can use to lower radon levels in your home. Some techniques prevent radon from entering your home while others reduce radon levels after it has entered. EPA generally recommends methods which prevent the entry of radon. Soil suction, for example, prevents radon from entering your home by drawing the radon from below the house and venting it through a pipe, or pipes, to the air above the house where it is quickly diluted.
We offer some tips on what to look for to check the contractor's work at https://www.epa.gov/radon/consumers-guide-radon-reduction-how-fix-your-home. Checking Your Contractors Work
Similar to a furnace or chimney, radon reduction systems need some occasional maintenance. You should look at your warning device on a regular basis to make sure the system is working correctly. Fans may last for five years or more (manufacturer warranties tend not to exceed five years) and may then need to be repaired or replaced. Replacing a fan will cost around $200 - $350 including parts and labor. It is a good idea to retest your home at least every two years to be sure radon levels remain low.
See "A Consumer's Guide to Radon Reduction" at https://www.epa.gov/radon/consumers-guide-radon-reduction-how-fix-your-home.