No owner or user of a boiler shall operate such boiler under pressure in this state without an operating certificate as provided for in section 29-238. Any person who operates a boiler without such certificate or at pressure exceeding that specified in such certificate shall be subject to the penalty provided by section 29-243. No boiler which does not conform to the provisions of this chapter or to the boiler regulations formulated or adopted by the board shall be installed in this state. All boilers shall be inspected during construction by an inspector authorized to inspect boilers in this state or, if constructed outside the state, by an inspector holding a commission from the National Board of Boiler and Pressure Vessel Inspectors and a report of each such inspection made available to the Commissioner of Administrative Services. This chapter shall not be construed as preventing the use or sale of boilers in this state which have been installed or in use in this state prior to October 1, 1953, and which have been made to conform to regulations for existing installations.