There are both manual lift chairs and gas lift office chairs. Pneumatic lift office chairs operate with a gas-filled cylinder that moves the chair up and down when pressure is applied with the levers. When a gas cylinder fails, it can be replaced.
Different parts of a gas lift chair can fail, causing different problems. Symptoms of a failed cylinder include the seat raising or lowering when not in use, a bent piston rod, no response when pushing lever and a seat stuck in a high or low position. If an office chair is experiencing any of these symptoms, the cylinder should be replaced.
It is important to purchase the right style and length of gas cylinder to replace the broken part. In order to measure the cylinder precisely, first remove the base of the chair. This will require turning it upside down, removing the clip and then removing the washer. Measure the exterior of the cylinder only--the body--not the internal device that moves up and down.
Cylinders can be ordered from an office supply store or online. Removing failed cylinders can be tricky. It is possible to remove the cylinder using a long pipe wrench. It can be easier to remove with a cylinder removal tool, which can be rented or purchased.