Historical boilers shall require an initial Certificate Inspection by an Authorized Inspector in accordance with The National Board Inspection Code, followed by a Certificate Inspection every three years thereafter if stored inside a shelter, or annually if stored outdoors. The initial Certificate Inspection shall include ultrasonic thickness testing of all pressure boundaries. Thinning of the pressure retaining boundary shall be monitored and recorded on the inspection report.
Ariz. Admin. Code § R20-5-432