What are the four major classifications of automatic sprinkler systems?

The four major classifications of automatic sprinkler systems are wet pipe, dry pipe, preaction, and deluge.

Wet pipe sprinkler systems are the most common type, where the pipes are filled with water and the system activates when a sprinkler head is activated by heat, allowing water to flow directly to the fire.

Dry pipe systems are used in areas where the risk of freezing is present. In these systems, the pipes are filled with compressed air or nitrogen; when a sprinkler head activates, the air is released, allowing the water to flow from a remote storage tank.

Preaction systems are a hybrid of wet and dry systems. They require two triggers to activate the water flow: typically, a heat-sensitive sprinkler head must activate, followed by a separate smoke or heat detection system. This provides an additional layer of protection against accidental water discharge.

Deluge systems are similar to wet pipe systems but are designed for high-hazard environments. When activated, they release a large volume of water through open sprinkler heads, which is ideal for controlling rapidly spreading fires.

These classifications are essential for understanding how various environments affect sprinkler design and how they function to suppress fire effectively.