Section 58B. The hours of duty of the permanent members of the uniformed fire fighting force in every city and town in which this section is accepted as hereinafter provided shall be so established by the fire commissioner, board of fire commissioners, chief engineer, board of engineers, or other officers having charge of fire fighting that the average weekly hours of duty in any year, other than hours during which such members may be summoned and kept on duty because of conflagrations, shall not exceed forty-eight in number; provided that any such city by ordinance and any such town by by-law may establish such weekly hours of duty at less than forty-eight. Sections fifty-six, fifty-seven, fifty-eight A and fifty-nine shall not apply to the permanent members of the uniformed fire fighting force in any such city or town.

Upon petition of not less than ten per cent of the registered voters in any city or town, duly certified by the registrars of voters and filed with the state secretary not less than sixty days before a state election, or filed with a city or town clerk not less than sixty days before a municipal election, the state secretary, or the city or town clerk shall cause to be printed upon the official ballot to be used in such city or town at such state or municipal election the following question:—''Shall section fifty-eight B of chapter forty-eight of the General Laws, providing for a forty-eight hour week for permanent members of fire departments, be accepted?'' If a majority of the votes cast on said question in any city or town are in the affirmative, this section shall take effect in such city or town ninety days thereafter.