What method do dry pipe sprinkler systems use for activation?

Dry pipe sprinkler systems are designed to be filled with pressurized air or nitrogen rather than water. This air pressure keeps the valves closed, preventing water from entering the pipes until the system is activated. When a fire occurs and the temperature rises, the heat from the flames causes a sprinkler head to open, allowing the pressurized air to escape. This drop in pressure then triggers the dry pipe valve to open, allowing water to flow into the pipes and out through the activated sprinkler head.

In this setup, the use of pressurized air is crucial because it helps prevent water from freezing in climates where temperatures may drop below freezing. These systems are commonly used in unheated buildings or areas with high risk for freezing pipes. The activation process relies entirely on the heat of a fire to trigger the system, without the need for manual intervention by firefighters at the initial stage.