D.C. Code § 2-107

The Boiler Inspector, or one of his assistants, shall inspect annually all boilers and unfired pressure vessels for which a certificate of inspection is required by § 2-105 and shall determine by actual tests the condition thereof from the standpoint of safety and fitness for operation. If such boiler or vessel be safe and fit for operation, the Boiler Inspector shall issue the certificate of inspection which shall state, among other things, the pressure per square inch such boiler or vessel may be allowed to carry. This certificate of inspection shall be displayed in a conspicuous place in close proximity to the boiler or vessel covered thereby. In the case of a steam boiler or unfired pressure vessel which is regularly insured and inspected at least once a year by an insurance company duly licensed in the District of Columbia and approved by the Mayor of the said District as to its inspection service where a report of such inspection filed within 30 days after such inspection with the Boiler Inspector shows any such boiler or unfired pressure vessel to be in a safe and insurable condition, such inspection and report shall take the place of the inspection hereinbefore provided and the certificate of inspection may be issued upon such report. Insurance companies shall report to the inspectors the cancelation of insurance of any certificate holder.