Foam Based A Class Water Type Stored Pressure Fire Extinguisher. Foam fire extinguishers can be used on Class A and B fires. They are most suited to extinguishing liquid fires such as petrol or diesel and are more versatile than water jet extinguishers because they can also be used on solids such as wood and paper. Stored pressure foam and water fire extinguisher are ideal for fires involving volatile liquids and freely burning materials such as paper, Cloth, wood and furniture. mechanical foam & water extinguishers are not suitable for fires Involving electrical risk.