For the division of loop System in fire fighting system, is it the same size or different riser?

This is a good and useful question, I wish to find acceptable answer

Are taking about Fire Suppression Systems as Sprinkler, Wet or Dry, or your taking about Fire Alarm Systems in Loop for detector in Fire Alarm, but let choose Sprinkler Wet Systems, the main intake will be most of the time between 8' Inch to 4" inch depending of the size and the level of the building, for the riser is go by different level of the building, divide by branch unit over each floor, if your not sure rather asking someone who's is more familiar with the installation of the systems, that could explain more at this present time. 

as per my knowledge remote area remains constant in boss loop and tree system so riser size will not be affected only the main loop pipe size will be changethis only a general knowledge no reference if there is any reference kindly advise

any loop systems have the sam size,