What is the key difference between closed and open fire main systems?

The key difference between closed and open fire main systems lies in the nature of how they are pressurized and the fluid they contain. Closed systems are indeed always pressurized, which means they maintain a certain level of pressure to ensure that water can be delivered effectively to fight fires. This pressurization helps prevent backflow and keeps the system ready for immediate activation.

In contrast, open fire main systems do not maintain a constant pressurized state. These systems typically rely on gravity or pumps to deliver water, and they may allow for variations in pressure depending on the operational requirements and conditions. Because of this fundamental difference in pressurization, closed systems are designed to ensure immediate readiness for firefighting, while open systems might take longer to become fully operational under certain circumstances.

This understanding clarifies the crucial operational characteristics of both systems and ensures that personnel know when and how to activate fire mains effectively in emergencies.