Section 61(14)(nn) in The Orissa Factories Rules, 1950
(nn)In any building not provided with automatic fire alarm, a manual fire alarm system shall be provided if the total capacity of the buildings is over five hundred persons or if more than twenty-five persons are employed above or below the ground floor, except that no manual fire alarm shall be required in one storey buildings where the entire area is undivided and all parts thereof are clearly visible to all occupants.