A product -of-combustion (heat, smoke, or flame) detector senses the presence of a fire condition.

The fire detection system sends a signal to the preaction valve, causing the valve to open.

Sensors in the piping system detect the flow of water into the system and trigger the water flow fire alarm.

When the level of heat at a sprinkler reaches the appropriate temperature, the sprinkler fuses and water flows through the open orifice.