It always depends on what you put in writing in your contract of sale. EPA action level is 4.0 pCi/L or more and if the level is less than that the contingency for radon is usually deemed to be satisfied. However, the buyer has the option of inserting a level they deem is appropiate for them even if lower than EPA mandate. They also have the option of wether they can declare the contracat null and void or to ask the seller to take remedial action if that level is higher than what they deem is appropiate. So read your contract first and find out what you agreed to. Also, if you have a buyer's agent representing you, talk to him/her about this issue. If it is that important to you, you should have made it known to your agent when writing up the contract of sale so he/she could have put in those contingencies to protect you. You cannot change your agreement after-the-fact with the seller unless the seller now also agrees to the change. It doesn't hurt to ask. Good Luck!