Which component of a fire sprinkler head holds the orifice cap in place until activation?

The heat-sensitive element is the correct answer because it plays a crucial role in the operation of a fire sprinkler system. This component is designed to respond to elevated temperatures caused by a fire. When the temperature reaches a certain threshold, the heat-sensitive element, which can be a glass bulb filled with liquid or a fusible link made of special metals, will break or melt. This action releases the orifice cap, allowing water to flow through the sprinkler head and extinguish or control the fire.

In contrast, other components do not serve this specific function. The pressure valve regulates the water pressure but does not retain the orifice cap. The activation switch is not typically a part of a standard fire sprinkler head; instead, it may refer to systems like alarms or fire suppression mechanisms. The flow control device manages water flow through the system, but it does not hold the orifice cap in place. Thus, the heat-sensitive element's direct involvement in the activation process makes it the essential component for this function.