When a contractor technician arrives at your UST facility to perform precision tightness testing of the tank and/or piping you should request that they present to you proof of their certification before allowing them to begin testing. If they are unable to present proof of certification you should immediately request this information from the contractor. If the contractor is unable to provide proof of certification the technician should not be allowed to perform any work or testing on the UST system.
There are also several approved methods for performing PTT for tanks and/or piping. Request from the contractor the information describing the type or method of PTT they use for tanks and/or piping. You can verify that the method has been reviewed and approved by the National Work Group on Leak Detection Evaluations (NWGLDE).