A resuscitator is a device using positive pressure to inflate the lungs of an unconscious person who is not breathing, in order to keep them oxygenated and alive. One basic type: a manual version (also known as a bag valve mask) consisting of a mask and a large hand-squeezed plastic bulb using ambient air, or with supplemental oxygen from a high-pressure tank. The other type is an oxygen powered resuscitator. These are driven by pressurized gas delivered by a regulator, and can either be automatic or manually controlled. Most modern resuscitators are designed to allow the patient to breathe on his own should he recover the ability to do so. All resuscitation devices should be able to deliver >85% oxygen when a gas source is available.