Nebulizers come in home (tabletop) and portable models. Home nebulizers are larger and must be plugged into an electrical outlet. Portable nebulizers run on batteries -- either disposable or rechargeable -- or can be plugged into a car's cigarette lighter. Smaller, portable units are slightly larger than a deck of cards, so they can be carried in a purse, briefcase, or backpack to be used whenever and wherever you need them.