Pull out the safety pin from the operating levers/handle that prevents the extinguisher being accidently discharged. There may also be a tamper evident seal fitted to the extinguisher; these are designed to break very easily as the safety pin is removed.
Aim the nozzle/discharge horn of the fire extinguisher at the base of the fire.
Completely squeeze the operating levers/handle in order to discharge the extinguisher, ensuring you are the appropriate distance from the fire.
Sweep the nozzle/discharge horn back and forth at the base of the fire to ensure it is extinguished. Be sure to keep going until the extinguisher is empty to avoid reignition.
*For Class F extinguishers (cooking oils), completely discharge the extinguisher into the deep fat fryer from a minimum 1m distance away, with the lance held directly above the burning oil.