(1) The rules and regulations formulated by the board shall have the force and effect of law, except that the rules applying to the construction of new boilers and unfired pressure vessels shall not be construed to prevent the installation thereof until twelve months after their approval by the director of the department of labor and industries.

     (2) Subsequent amendments to the rules and regulations adopted by the board shall be permissive immediately and shall become mandatory twelve months after such approval.

[1951 c 32 § 5.]