Using a dry powder fire extinguisher requires some skill as the technique is different to using some other types of extinguisher, and individuals should always be trained in using one if the extinguishers are present. For fires involving liquids in containers or spilled liquids, the nozzle needs to be directed at the near edge of the fire, and a rapid sweeping motion of the nozzle applied gradually towards the far edge. On fires involving flowing liquids, the nozzle should be directed at the base of the flames and swept upwards. If electricity is involved (or suspected), the main supply must also be shut off before any attempts to tackle the fire are made.