Section 393-18 - Termination of exemption(a) If an exemption which has been claimed by an employee pursuant to section 393-17 terminates because of any change in the circumstances entitling the employee to claim such exemption, the employee shall promptly notify the principal employer of the termination of the exemption and the employer thereupon shall provide coverage as required by this chapter.(b) If because of a change in the employment situation of an employee or a redetermination by an employee as provided in section 393-6, a principal employer becomes a secondary employer or a secondary employer becomes the principal employer, the employee shall promptly notify the employers affected of such change and the new principal employer shall provide coverage as required by this chapter.