Which sprinkler system has air in piping, water flow control, fire detection devices, and closed sprinklers?

• A. Wet
• B. Dry pipe
• C. Preaction
• D. Deluge

Answer: (C)

Preaction systems keep the piping dry and require a two-step release before water reaches the sprinklers. The pipes are filled with air (not water) and are equipped with fire detection devices that must be activated first. When a detector signals a fire, a water-control valve admits water into the system, but the sprinklers themselves remain closed until the second step occurs (typically heat at a sprinkler head or an additional interlock), preventing accidental discharge. This combination—air in the pipes, a water-release valve controlled by detectors, and normally closed sprinklers—fits the preaction setup best. Wet pipe systems have water-filled piping and open sprinklers; dry pipe systems also use air in the pipes but do not rely on fire detectors to release water into all heads; deluge systems have water-filled piping with all sprinklers open.