The most commonly used high-pressure gas cylinders are designed to hold gases at pressures to 2400 psig; some ultra-high pressure commercial cylinders will contain gas at pressures to 6000 psig.

The g in the psig pressure designation refers to pressure measurement in pounds per square inch at the cylinder regulator gauge. The gauge measures the gas in the cylinder at a pressure above the outside atmospheric pressure. If the gauge reads zero and the cylinder is at sea level, the cylinder still contains gas at 14.7 psi absolute pressure. Therefore, the primary safety rule for handling compressed gases is: An empty cylinder is never out of gas. The same handling rules apply to it that apply to a full cylinder of the same gas.

High-pressure cylinders come in a variety of pressure ratings and capacities. The most commonly used cylinders for oxygen, nitrogen, argon, and helium are rated at 2400 psig. The amount of gas in the cylinder will depend on the gas, because compressibility factors differ. At 2400 psig, a typical industrial cylinder will contain 251 cu ft of oxygen or about 291 cu ft of helium. Other commonly used cylinders are 2485 psig units, which contain 276 cu ft of oxygen, and 2640 psig cylinders, which contain 330 cu ft of oxygen.

The common 2400 psig, 251 cu ft oxygen cylinder weighs about 150 pounds, depending on the grade of steel used in the cylinder body. Each cylinder has a valve on top and a steel cap that screws over the valve to protect it from damage. Each valve has a safety device designed to release pressure if the cylinder pressure becomes too high.

If the valve of a high-pressure gas cylinder is broken off, the contents of the cylinder will jet from a hole about the diameter of a pencil. The escaping gas could have enough thrust to turn the cylinder into a rocket, depending on the cylinder's size and weight.