Section 120.657 - Power Failures(A) If electrical power at a panoramic irradiator is lost for longer than ten seconds, the sources must automatically return to the shielded position.(B) The lock on the door of the radiation room of a panoramic irradiator must remain locked in the event of a power failure.(C) During a power failure, the area of any irradiator where sources are located may be entered only when using an operable and calibrated radiation survey meter.