The best way to understand how gas struts work is to know how they are made. Gas struts consist of a piston or rod, which is contained within a larger housing tube. The housing tube is usually made of steel and coated to reduce friction, because the piston end of the strut will slide up and down inside this tube. Gas struts can be made of stainless steel as well, and these are used in environments where rust is a major concern, such as in the fishing industry.
A gas strut, like an air or hydraulic strut, operates on compression. When force is applied in an air or hydraulic strut to the end of the smaller piston rod, the fluid or air is forced through a hole, thus causing resistance. In a gas strut, the internal gases do not leak through a hole. Rather, when force is applied, the gases are compressed (they can be compressed to a certain value), and this alone causes resistance. Gases naturally try to expand, so once the pressure is released, the gas expands again and forces the piston to return to the extended position.
A gas strut works in many ways on many types of equipment. However, they do not perform as well in the cold weather. Because of this and other reasons, they are not generally used in cars. They are used on doors (such as a hatchback boot) or on special car top carriers. They can also be used in many different types of mechanical equipment.