All boilers included under this chapter shall be inspected by a state boiler inspector or by a special inspector employed by an insurance company licensed to insure boilers in this state as follows:

(1) Power boilers, meaning boilers operating at steam or vapor pressures in excess of fifteen pounds per square inch gauge, except power boilers that operate with internal water treatment under the direct supervision of a qualified engineer, shall be inspected each year. Such boiler inspection shall consist of (A) a thorough internal and external inspection while not under pressure, and (B) an external inspection under operating conditions not more than six months after the internal and external inspection. No more than fourteen months shall elapse between internal inspections and between external inspections while under pressure.

(2) Power boilers that operate with internal water treatment under the direct supervision of a qualified engineer shall be inspected every eighteen months. Such boiler inspection shall consist of (A) a thorough internal and external inspection while not under pressure, and (B) an external inspection under operating conditions not more than nine months after the internal and external inspection.

(3) Where construction will permit, low pressure steam or vapor heating boilers, hot water heating boilers, hot water supply boilers and hot water heaters shall be inspected externally biennially and internally at the discretion of the boiler inspector. If a boiler inspector decides a hydrostatic test is necessary to determine the safety of a boiler or heater, such test shall be made under the inspector’s direction. The Commissioner of Administrative Services may order inspections by the Department of Administrative Services or the insurance carrier in addition to the regular annual or biennial inspections to clear up any doubts as to the safety of continuing the operation of any boiler or heater included in this chapter. Each boiler insurance carrier shall forward to the commissioner, not later than thirty days after each inspection as required by this chapter, a report of such inspection upon appropriate forms as promulgated by the commissioner, who may use the form suggested by the American Society of Mechanical Engineers.