Dry powder extinguishers:
The approximate effective range of a 9kg unit is 4m – 5m.
The powder cloud tends to interfere with the chemical reactions inside a flame thereby achieving extinguishment. The operator should stand back initially to allow the powder stream to fan out.
Care should be taken not to direct the powder jet into the burning liquid as this would splash the liquid out of the container and spread the fire.
For fire involving electrical equipment, try to get the powder to penetrate motor casings, switchboards etc.
For gas fires direct the powder into the flame from behind the leak. The gas supply should be immediately cut off to avoid a gas build up. The use of an extinguisher on a gas flame should only be considered as a last resort.