A normally closed valve is a type of electromechanical device with a plunger that remains closed until it receives energy in the form of an electrical impulse. It can control the flow of fluids, air, and other gases in a wide range of applications, including HVAC systems, plumbing systems, locking mechanisms, and safety shut-off systems. A normally closed valve is typically activated only for short periods of time, making it an energy efficient option.