A  lot of homes in the Shenandoah Valley and in Northern Virginia do test  positive for "Radon Gas" and one does not know unless you properly test.Nowadays  in a real estate transaction you only have a short window to have a  home inspection and/or a radon test. Some of the inspection companies  out their do not invest in the proper testing equipment for real estate  transaction, due to the cost of the machine, but still charge you the  same fee to conduct a proper test. Now whether its a Eperm, Charcoal  Canister or a Continuous Radon Monitor (CRM) all can give you accurate  readings, but the first two are passive and allows for the test to be  interfered with or compromised (cheated). A CRM type monitor on the  other hand give you an hourly reading and lets technician know if the  test was interfered with or compromised in anyway. I cannot tell you how  many time people call me in to mitigate a home and when they bought it,  the passive test showed everything was fine and now 10 years later when  they go to sale they found out different and had a much different  reading and  have exposed their family to high levels of radon over the  years.Now  even when a proper test has been conducted that test only is telling  you what the radon levels were in that 48 to 90 hour window. If your  test was conducted while the A/C was running, the cold air actually  keeps the radon in the ground, whereas when you turn the furnace on the  heat rises in a home creating the "Stack Affect" and as air escapes  through the upper thermal plane of the home that make up air has to come  from somewhere and typically is pulled up from the basement slab. the  longer the test the more accurate the test. A very accurate long term  test is  called a AlphaTrack, which runs for a minimum of 90 days to a  year and you live your life normally( no closed house conditions need to  be kept. I am not a big fan of the ones you buy at a big box store,  since the reading is only as good as the lab annualizing it.  We  recommend Accustar to our customers in need of long term or short term  testing devices to conduct your own testing at home.Some  of the counties in the area require the builder to install a passive  system in a new home, but you still need to test to see if the system is  actually working and the sump pump needs to be sealed as well. 

 We  have been designing and installing Radon Mitigation Systems for the  past 16 years and have installed thousands of system that are still  functioning today.
With  FRES you will never just get a guy in truck that is not licensed to  install systems or who has not had the proper training or education. You  call FRES and you get me and all my years of experience and education  in designing and installing Radon Mitigation Systems.  We have all the latest diagnostic testing equipment and have never  failed in getting the radon level down and in most cases we achieve  levels below 1pCI/l.
We use RADONAWAY fans that are guaranteed from the manufacture for 5 years We  do not use cheap downspout guttering in our systems nor do we use the  sump pump lid, like most of our competition. If the sump pump needs  servicing then the radon system has to be dismantled, we choose to core  drill thru the concrete slab for a better system and better results The average cost for a Radon Mitigation System generally runs between $800.00 to $900.00(And that price includes all retesting as well)