Red Seal Gasfitter — Class B Practice Exam

Which component ensures that gas is only delivered on demand to an appliance?

1. A constant flow gas valve

2. A demand-controlled gas valve

3. A pressure regulator

4. A gas meter

The correct answer is: A demand-controlled gas valve

The demand-controlled gas valve is designed to deliver gas to an appliance only when needed. It operates based on the demand created by the appliance, ensuring that gas flow is optimized for efficiency and safety. When the appliance requires gas, the valve opens to allow the appropriate amount of gas to flow, but when there is no demand, the valve closes, stopping the gas flow. This mechanism is important for minimizing gas waste and improving the overall efficiency of the gas system. While the other components listed have important roles, such as regulating pressure and measuring gas usage, they do not specifically function to deliver gas only when required by an appliance. The constant flow gas valve would allow for a continuous flow regardless of demand, the pressure regulator maintains a specific pressure level but does not control delivery based on appliance needs, and the gas meter tracks consumption but does not control the flow itself. Thus, the demand-controlled gas valve is the only component specifically designed for on-demand gas delivery.