The Laws of Body Inflation
Law of Pneumatic Economy: Compressed gasses are so cheap as to be practically free. Thus various people and organizations who have no particular reason to keep tanks of compressed gas around do so just in case they're needed someday.
Law of Containment Durability: Devices which are designed to contain or convey compressed gasses (tanks, hoses, pumps, etc) are made from highly durable materials and engineered to a level suitable for high-end aerospace applications. As such, they will never fail even when under extreme stress and operating well outside of their design specifications.
Law of Excess Capacity: Because compressed gasses are free and the tanks are nigh indestructible, it's fairly routine for a vessel to contain a quantity of gas that's far greater than what's required for its intended purpose. Thus you'll often find a blimp's worth of helium in a tank used for filling party balloons.
Law of Pneumatic Control Fragility: Kn