Section 1. The Board of Trustees of any firemen’s pension fund in any incorporated city or town in this State may, upon fulfilling requirements hereinafter stated, establish benefit eligibility for a fulltime employee who has been employed for as long as six (6) years, and thereafter becomes disabled or dies from heart or lung disease, based on a presumption that such death or disease was a consequence of his duties as a fireman, if the fireman shall have successfully passed a physical examination prior to the claimed disability or death, or upon entering upon his employment as a fireman, and the examination failed to reveal any evidence of the condition or disease of the lungs, hypertension or heart disease.

Sec. 2. Before any such Board shall adopt as part of its plan for retirement benefits the presumption, together with qualifications, set forth in Section 1 hereof, it shall take the following preliminary step(s):
(a) Obtain an actuarial study showing how the proposed change in benefit eligibility standards will affect the financial condition of the fund.
(b) In the event that such actuarial study shows that inclusion of the proposed change in benefit eligibility standards will not make the fund financially unsound, then said Board shall, within thirty days after receipt of such actuarial study, hold an election in which the active participants contributing to the fund shall vote on the question of whether such benefit eligibility standard should be instituted, said Board being bound by the results of such election.