The National Environmental Health Association and the National Radon Safety Board administer voluntary National Radon Proficiency Programs for radon professionals consisting of individuals and companies wanting to take training courses and examinations to demonstrate their competency.[98] Without the proper equipment or technical knowledge, radon levels can actually increase or create other potential hazards and additional costs.[109] A list of certified mitigation service providers is available through state radon offices, which are listed on the EPA website.[110][109] Indoor radon can be mitigated by sealing basement foundations, water drainage, or by sub-slab, or sub-membrane depressurization. In many cases, mitigators can use PVC piping and specialized radon suction fans to exhaust sub-slab, or sub-membrane radon and other soil gases to the outside atmosphere. Most of these solutions for radon mitigation require maintenance, and it is important to continually replace any fans or filters as needed to continue proper functioning.[3]