A dry powder fire extinguisher is effective for 

Class A (organic materials), 

Class B (flammable liquids), 

Class C (flammable gases), and electrical fires.

It contains mono-ammonium phosphate mixed with other powders to fight fires. The fine powder absorbs fuel molecules and acts as a shield against radiated heat. 

Dry powder extinguishers are suitable for normal combustible materials, flammable liquids, and fires involving electrically energized equipment.

A wide range of sizes is available with the following ratings

1kg - 8A 34B C

2kg - 13A 70B C

3kg - 13A 89B C

4kg - 21A 89B C

6kg - 27A 144B C

9kg - 34A 233B C