53 Pa. Stat. § 13348
The director, or other officers of the department having charge of the fire bureau in each city of the first class, shall divide the officers and members of the companies of the uniformed fire protection forces in the employ of such cities, excepting the chief engineer and assistant chiefs and those employed subject to call, into two bodies or platoons. One to perform day service and the other to perform night service. The hours of day service shall not exceed ten commencing at eight o'clock in the morning, and the hours of night service shall not exceed fourteen commencing at six o'clock in the afternoon. The hours of day service shall not exceed thirty hours, and the hours of night service shall not exceed forty-two hours in the same calendar week. The employes of such fire forces shall be allowed to have at least twenty-four consecutive hours of rest in every calendar week exclusive of the change day, and to have an annual vacation of not less than fourteen days without diminution of, in either case, of the salary or compensation fixed by ordinance or resolution. But no vacation or suspension period shall be increased or reduced by reason of the fact that, during such period, such member, if working, would have been entitled to one or more rest days under the provisions of this act. In case of public celebrations, riots, serious conflagration, floods, times of war, pestilence or such emergencies, the chief engineer in charge of the bureau of fire or the assistant chief deputy or chief officer in charge at any fire, shall have the power to assign all members of the fire protection forces to continuous duty or to continue any members thereof on duty if necessary. No member of either said shifts, bodies or platoons shall be required to perform any longer day duty than thirty hours of day service or forty-two hours of night service in the same calendar week, excepting as may be necessary to equalize the hours of duty and service, and also excepting in case of emergencies as above provided.
53 P.S. § 13348