What is the pressure condition of the air in the pipes of a deluge system?

In a deluge system, the air in the pipes is not under pressure, which is essential for the system's proper operation. This design allows for a swift release of water when activated, as deluge systems are typically initiated by the opening of a valve, which can be triggered by heat or smoke detection. The lack of pressurized air prevents unintended discharge and ensures that when the system is activated, it can rapidly fill the pipes with water to combat a fire effectively. The straightforward air pressure condition contributes to the reliability and safety of the fire protection system without unnecessary complications that might arise from maintaining a pressurized atmosphere.