In a dry pipe sprinkler system, what prevents water from entering the pipes?

In a dry pipe sprinkler system, pressurized air or nitrogen is utilized to keep the water out of the system's pipes. This pressurized gas fills the space above the water in the system piping and helps maintain a dry environment. When a fire occurs and a sprinkler head operates, the pressurized air or nitrogen is released, allowing the dry pipe valve to open, and water can then flow into the system to reach the activated sprinklers.

This mechanism is critical as it allows the system to remain functional in environments where the temperature could drop below freezing. By using pressurized air or nitrogen, the risk of water freezing and causing damage to the pipes is eliminated, making this approach ideal for buildings that are unheated or see low temperatures.