Gas valves are used to control the flow of gas only when it is safe to open and ignite the gas. There are two major styles of gas valves; intermittent and standing pilot.

  A intermittent gas valve has a electronic coil that opens the valve when it is energized. These valves are redundant. Meaning that when the valve opens, there are actually two ports that open at the same time. So if the valve were ever to fail in the open position, a gas leak would occur only if both ports went bad at the exact same time. This is a very unlikely event.

A standing pilot gas valve has a pilot light that heats up a thermal coupler. When the thermal coupler is heated, there is a 24VAC electrical signal that is sent to the gas valve. When the electrical signal is recieved by the valve, the valve is safe to open and the gas will be ignited. The standing pilot gas valve is also redundant, so there is a minimal chance of the valve opening and leaking gas.

intermittent gas valves		standing pilot gas valves