Which valve type remains closed until a sprinkler head opens?

The option that correctly describes the valve type that remains closed until a sprinkler head opens is the alarm valve. An alarm valve, which is a critical component of a fire protection system, is designed to remain closed until a specific condition occurs, such as the operation of a sprinkler head due to heat from a fire.

When a sprinkler head activates, it allows water to flow through the system. The alarm valve then opens to allow water to discharge in the area needing protection. This operation triggers the alarm to notify occupants and emergency services about the presence of a fire. The design of an alarm valve ensures that water is present in the system and only released when needed, helping to prevent water damage in areas where a fire is not occurring.

In contrast, other types of valves mentioned have different operations. For example, a dry-pipe valve is used in systems where water is held back until a sprinkler head opens, but it holds compressed air or gas in the system. A deluge valve opens all sprinkler heads simultaneously, providing a large volume of water when there is an alarm activation. A check valve is used to prevent backflow in piping systems and does not relate to the operation of sprinkler heads.