53 Pa. Stat. § 801
The head of the department of public safety, or of the department having charge of or supervision over the fire department or bureau, in each city of the first, second and third class shall, from and after the first day of January, one thousand nine hundred twenty, divide the officers and members of companies of the uniformed fire force in the employ of such cities, or, in the case of a volunteer fire department, the firemen and drivers regularly employed and paid by the city, excepting the chief engineer and assistant chiefs, into two shifts, 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; the hours of night service shall not exceed fourteen, commencing at six o'clock in the afternoon. In cases of riot, serious conflagration, or other such emergency, the chief engineer 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 the members of the fire force to continuous duty, or to continue any member thereof on duty, if necessary. No member of either of said shifts, bodies or platoons shall be required to perform continuous day service or continuous night service for a longer consecutive period than two weeks; nor be kept on duty continuously longer than ten hours in the day shift, body or platoon, or fourteen hours in the night shift, body or platoon, excepting as may be necessary to equalize the hours of duty and service, and also excepting in cases of riot, serious conflagration, or other such emergency, as above provided: Provided, however, That this act shall not apply to employes who are employed subject to call. In any consecutive period of two weeks, no member of either of said shifts, bodies or platoons, in any city of the second class, shall be kept on duty for a total period which shall average over fifty-five hours in any one week of the consecutive period of two weeks.
53 P.S. § 801