Power Tank System w/ 15lb Polished BottleThe POWER TANK has the power and speed of a belt driven (A/C) compressor and the portability and lower cost of some 12 volt compressors. The POWER TANK can air up a 33 truck tire in less than one minute, remove a stuck lug nut in two seconds using a 1/2 impact wrench, and quickly reseat a tire while the wheel is still on the vehicle. And portability is a must when you need to help a friend who is difficult to get to. No other air system can do all of this - at any price. The concept is simple. The POWER TANK stores its massive amount of energy as liquid CO2. The liquid CO2 evaporates inside the aluminum cylinder and builds pressure which is released as a vapor gas (compressed air) through the regulator. As the gas is used, more liquid evaporates inside the aluminum cylinder thus regenerating the pressure. Once the cylinder pressure reaches a certain level - normally 700 - 800 p.s.i. - the evaporative process stops until gas pressure is released again. CO2 gas is non toxic, non-corrosive, and totally inert. This means it is safe on your air tools, rubber tires, and metal wheels. And the thermal expansion rate of CO2? - Similar to air.