A. The maximum allowable working pressure of a boiler stamped with the American Society of Mechanical Engineers Code symbol or a pressure vessel stamped with the American Society of Mechanical Engineers or American Petroleum Institute--American Society of Mechanical Engineers Code symbol shall be determined by the applicable sections of the code under which it was constructed and stamped.

B. The maximum allowable working pressure of a boiler or pressure vessel which is not stamped and does not carry the ASME or the API-ASME Code symbol shall be computed in accordance with standard engineering practice using a factor of safety established by rules adopted by the Commissioner of Labor.

C. This act shall not be construed as in any way preventing the use, sale or reinstallation of a boiler or pressure vessel referred to in subsection B of this section, provided the Commissioner of Labor gives a specific ruling that such boiler or pressure vessel conforms to its rules and regulations, and provided further, upon inspection it has been found to be in safe condition.

D. If a boiler or pressure vessel is of historical significance and cannot comply with the construction requirements of the rules and regulations of this act, a special installation and operating permit may be granted by the Commissioner.