The duties of the first assistant and the deputies shall be to operate under the direction of and to assist the State Fire Marshal in the execution of sections 81-501.01 to 81-531 and 81-5,151 to 81-5,157, the Nebraska Natural Gas Pipeline Safety Act of 1969, the Petroleum Products and Hazardous Substances Storage and Handling Act, and any other statutory duties imposed upon the State Fire Marshal. In the event of a vacancy in the office of State Fire Marshal and until a successor is appointed or during the absence or disability of that officer, the first assistant fire marshal, with the assent and approval of the Governor, shall assume the duties of that office.