When doing the hydraulic calculations for an open space (having only upright sorinklers), we calculate the No. of sprinklers based on the Max. protection area and the Area of coverage (ex: 1,500 ft2 / 130 = 11.5 = 12 sprinklers). In case we have the same area, same hazard, but the area is not an open space, it has a false ceiling (open office space for example) and we have upright and pendent sprinklers.

1-The 12 sprinklers shall be doubled? (considering 24 sprinklers to cover the area above and below false ceiling?)

or

2-The 12 sprinklers will be considered to cover above false ceiling OR below false ceiling since fire cannot happen simultaneously?

3-any other consideration?

Thank You

I believe we need a little more information to properly answer the question. Is the false ceiling a typical lay in acoustical tile arrangement? What is the elevation of the false ceiling above the floor? If the space is an open office how did you arrive at the max. allowable spacing per sprinkler as 130 square feet? Is the area above the false ceiling combustible? If the space is combustible, how much vertical space is there above the false ceiling? Is the space above the false ceiling flat or pitched? Does the false ceiling extend all the way to the walls of the space or is it a cloud?