Nozzles are used in fluid bed combustion boilers. These are manufactured in various chemical compositions to suit the different fuels used in the boilers.

Energy is required to break up the oil into droplets. The energy is supplied by the fuel unit delivering oil to the nozzle from 100-150 PSIG for most residential applications and up to 300 PSIG for commercial applications. The nozzle, through the swirl slots, swirl chamber and orifice convert the energy from pressure to velocity.