What are the different types of water mist water supply methods?

Water mist can be delivered either through a pre-pressurised system (stored water and propellant gas in cylinders) or a flow-generating device (a pump) through the system’s distribution pipework to the discharge nozzles using either a single or twin fluid delivery system.

Single Fluid Pumped

A single fluid system generates water mist by delivering water through the nozzle under pressure from either a low- or high-pressure pump system.

Single Fluid Pressurised

A single fluid system generates water mist by delivering water through the nozzle under pressure from pressurised gas cylinders. The inert gas (usually nitrogen) does not mix with the water being pressurised; it is only used for flow-generating purposes.

Twin Fluid

A twin fluid system generates water mist by mixing an inert gas or air fed from separate pipework to the water supply pipework, that mixture being delivered to the activated nozzle/s under pressure. The inert gas helps the fire suppression effect by helping remove the oxygen from the fire environment, but it also creates a more hazardous atmosphere to occupants (if present) which is why this is typically used in normally unoccupied rooms or compartments.