Which type of fire is a Class B fire extinguisher is designed to put out?

The purpose of having an extinguisher rated on class B fires is so that such an extinguisher is capable of extinguishing any incipient flammable liquid as designated in the US by the NFPA or in Europe and the rest of the world by BSI or EN3 reliance.

The problem with most class B rated portable fire extinguishers is that almost all of them are not capable of extinguishing all of the subclasses of fuels defined under this category of fires. For example, in the class B definition of fuels there are 2-types: Polar and Non-Polar fuels and under the Non-Polar category there are 2-divisions that clearly require separation because of their different properties requiring different extinguishing medias to neutralized them if ignited. This is gasoline, their heavier varieties of products, and their lighter products used as solvents versus grease and cooking oil medias that exclusively and safely require them to be extinguished by their own category of chemical that are designed to qualify under the "K" fire class ratings.

The only product in the world that can extinguish all the class B fires including class K is only available by the newest Technology and steam of fire extinguisher products known as FireStopper® containing the exclusive extinguishing agent PFE-FR™, a Non-Toxic, Non-Irritant, and Non-Agressive, all fire class effective fire extinguisher and media.