Class BC extinguishers handle both Class B (flammable liquid) and Class C (energized electrical equipment) threats. These are typically used in areas that have a high threat from flammable liquids and electronics/machinery. Pound for pound, these units will generally fight a flammable liquid fire more effectively than a Class ABC extinguisher. You may still need Class A protection so sometimes it might serve well to have both kinds on hand. You can go back to the By Class page and to view your other class options.
While carbon dioxide units will fight flammable liquid fires, they do not leave a residue behind that can prevent reignition. Therefore, it is generally recommended that you select a dry chemical agent for such threats. One of the best dry chemicals for BC fire is Purple-K.