An alternative to the pilot light is a system to create a high voltage electrical arc or spark between two electrodes, in order to light the gas flowing to the burner. Fail-safe design for such a system requires the burner flame to be detected by passing an electric current through the flame, which is received by the flame rectification circuit inside an ignition controller connected to the gas valve. Flame rectification occurs when electrons flow through the flame burning, which the ignition controller senses and knows the flame is there, keeping the gas valve open. If the appliance loses gas or the flame goes out, the ignition controller doesn't see the flame, closing the gas valve.
A red-hot surface can also be used to provide ignition. Such igniters are often made of silicon carbide, silicon nitride, or another material that is durable under prolonged exposure to extreme heat. Hot-surface igniters are commonly used in cooking ovens, boilers, and modern gas furnaces.