P.A.L.S.S. Up Close
 

This is a prototype of the P.A.L.S.S. box.  It shows the water pipe entering through the top of the ceiling.  The polymer crystals are stored in the tank.  They are the size of  fine sand.  The fill valve is used to refill the polymer tank.  The heat and smoke sensor is responsible for starting the system.  During a fire, the water enters the tank and forces the polymer to expand to 1,000 times its size.  The sprinkler head sprays out hydrated polymer crystals onto the fire.