Foam extinguishers are fire safety devices designed to combat flammable liquid fires, such as those involving petrol or oil. They work by creating a blanket of foam that smothers the flames, cutting off the fire's oxygen supply and cooling the burning material. These extinguishers are effective on Class A fires (solid materials) and Class B fires (liquids). Typically, foam extinguishers are red with a cream label, indicating their specific use. They are commonly found in commercial and industrial settings, as well as in some residential areas. Proper training in using foam extinguishers is essential for effective fire response.