SPRINKLER TRAP

Glass bulb sprinkler heads have a small glass reservoir that holds a heat-sensitive liquid. This glass bulb holds the pip cap in place. When the ambient temperature of the liquid reaches a certain level, the liquid expands causing the glass bulb to break, which allows the pip cap to fall away releasing water. As with the fusible link heads, water is only released where the ambient temperature reaches a certain level, which helps limit water damage.