There are some contractors out there that are claiming to be certified but have not taken the necessary training to become certified. There are two national organizations that certify contractors, NEHA- National Environmental Health Association and NRSB- National Radon Safety Board. If a radon mitigation company is not listed on either of these two sites than they are not certified. NYS also has a website and you have to be certified to be on it. Many banks are now requiring certified contractors to have competed the work for a real estate transaction before they will fund the loan. In short, certified contractors have taken the necessary steps like all licensed trades to go through the training needed to promote professionalism and stay on top of current standards.