In which type of sprinkler system does air or nitrogen under pressure replace the water?

In a dry pipe system, air or nitrogen is maintained under pressure within the piping until a fire is detected. When a fire occurs and activates the smoke detectors or the sprinkler heads, the pressure in the system drops, allowing the valves to open and water to flow into the piping and out through the sprinkler heads. This type of system is particularly useful in environments where the risk of freezing is a concern, as the pipes do not contain water until needed.

The use of compressed air or nitrogen allows the system to remain dry and prevents the potential freezing of water in the pipes, making it ideal for unconditioned spaces like warehouses or attics. This system provides a reliable method of delivering water to control fires while mitigating the risks associated with freezing pipes in cold environments.

Other sprinkler systems, like the wet pipe system, contain water at all times and have no pressurized air component, making them unsuitable for areas prone to freezing. The pre-action system combines elements of both dry and wet systems, incorporating an initial air pressure but also requiring both a fire detection component and water supply to activate. The deluge system, on the other hand, is designed for areas with a high risk of uncontrolled fires and delivers large amounts of water through open sprinkler heads,