A pre-action sprinkler system is a fire suppression system that uses air pressure and water to extinguish fires. It’s designed to reduce the risk of water damage and false alarms. How it works 1. The system’s pipes are filled with compressed air and the sprinkler heads are closed. 2. When a fire is detected, the pre-action valve opens, allowing water to flow into the pipes. 3. The sprinkler heads open individually to release water onto the fire