Fuel-fed ignitors initiate the boiler flame in coal-fed plants using natural gas or atomized fuel oils such as light grade #2 or heavy grade #6. Natural gas and propane can also be used. In combined-cycle plants, gas turbines often use natural gas and liquid fuel oils as ignition fuel. Large gas turbines are designed to operate alternately or simultaneously with both gas and liquid fuels. In dual-fuel plants, a False Start Tank will temporarily hold diesel fuel after an unsuccessful attempt to fire the turbine.
Crude oils with lower flash points represent a greater fire hazard and require more extensive fire protection systems. Switches and transmitters should be safety certified.