While there are numerous options when it comes to a fire sprinkler head, they all perform the same basic function: containing and extinguishing fires. Most sprinklers are composed of a plug, a temperature-sensitive glass bulb, a deflector, and a frame. Functionally, it is fairly simple. The glass bulb is filled with a glycerin-based liquid which expands to break the bulb at a specified temperature. Once that happens, the flow of water held back by the bulb flows out towards the deflector which disperses it on to the fire.