If you are using a buyer's agent to represent you (and you absolutely should), your agent should have provided you with the resources to understand radon and its mitigation. I have a useful link below. I would also suggest that your agent help you understand the common occurrence of this in our area, and its insignificant impact on the salability of a home. In addition, opening a dialogue with the sellers would be a wise choice rather than terminating the contract if it was a home you wanted. The sellers may have felt it was not applicable since the radon levels were mitigated. The listing agent does not complete the Seller's Property Disclosure, so they would not have been advised regarding identifying the system. I would advise my clients to ask the sellers why the system wasn't identified before becoming concerned about other items not being disclosed. Also, keep in mind that the Seller's Property Disclosure is a helpful document; however, the inspection and due diligence are how you do you research and make your decisions.
Radon tests are common in real estate transactions in Colorado (because radon is common), and a continuous 48 hour radon test typically costs about $100. That would assure you that the installed system is working and the home is within acceptable levels.
Hope this helps!
I would think having a radon mitigation system in the home would be a positive. I'm starting to have my buyers do radon testing as part of the home inspection. If the home has elevated amounts of radon we ask for a mitigation system to be installed. Radon is the second leading cause of lung cancer behind smoking. Most relocation companies are now offering radon testing and mitigation as a free option for the buyers of their homes. Ask to have the home tested for radon, the test takes a few days and cost less then one hundred dollars. If the amounts are high ask the seller to update the system and retest until the home is safe.
Having a radon mitigation system does not reduce the salability of a home. I have sold properties in the past and recently that had radon mitigation systems. Working with both sellers and buyers. Niether party gave it serious weight if it was corrected.
As an aside, Sellers sometimes will mark n/a or no if it has been fixed. If you really liked the house, It would be good to chat with the seller or seller's agent about that item and any other items you may have concerns about to ease any questions or doubts you have.