Gas springs are charged with nitrogen gas to a high pressure and the gas is sealed inside the spring. The gas pressure acts on the piston rod or the piston (depending on design) of the spring and provides a resistant force. By using the equation Force = Charge Pressure times the Area of the piston, the initial force of the gas spring is calculated.
The larger the effective cross sectional area of the piston rod or the piston, the more “powerful” the gas spring will be. When the gas springs are compressed, the movement of the piston rod or the piston displaces gas volume resulting in increased spring force.