Which type of sprinkler system is filled with air until activation?

The sprinkler system that is filled with air until activation is characterized by its dry pipe design, which is specifically intended for areas that may be susceptible to freezing temperatures. In this system, the pipes are filled with pressurized air rather than water. When a fire occurs, the heat causes the sprinkler head to activate, releasing the pressurized air and allowing water to flow into the pipes and out through the open sprinkler heads.

This design offers an advantage in environments where traditional water-filled systems might freeze, thereby preventing potential pipe ruptures and ensuring that the system operates effectively in emergency situations. The air pressure holds back the water until needed, which is a crucial safety feature in many applications, especially in unheated spaces.

In contrast, other systems like wet pipe systems have water already in the pipes and are immediately operational upon activation. Pre-action systems require the activation of a detection system before water can flow, adding an additional layer of safety. Deluge systems, on the other hand, are designed to release large amounts of water simultaneously from all open sprinkler heads without relying on air pressure to hold back the water. Each of these systems has different functional characteristics tailored to specific environments and fire protection needs.