The gas cylinder in an office chair works as a lift spring for raising the seat height and holds it at the selected level. Typically the gas cylinders are the first components that wear out in chairs. In most cases it costs less to repair office furniture than it does to replace it, so frugal companies elect to pay for repairs. Most office chairs share similar construction, but not all are identical. Gas cylinder removal and replacement is essentially uniform for caster-based swivel chairs.
Wear eye protection. Chair parts may be propelled into the air during removal and it's possible for the pressurised gas cylinder to puncture and emit a sudden spray of gas.
Remove the chair base. Lay newspaper over three square feet of floor. Support the chair on its seat edge and back with the base protruding at an angle over the papers. Locate the clip on the underside of the central base where the base fits over the chair post. Slip a slotted screwdriver blade under the upper piece of the clip. Turn the screwdriver to pry the clip open and push it toward its curved bend until it slips off. Pull off the washer ring and remove the base. Take out the bearings and the two surrounding washers along with the rubber bumper. Gently pry these parts off the pencil-sized piston rod on the gas cylinder with a screwdriver blade if they don't freely fall out. Take note of the order in which the washers, bearings and rubber bumper are stacked on the piston rod in case they are suitable for reinstallation.
Inspect the inner parts. Check the rubber bumper for cracks, tears or excessive wear. Make sure the bearing retention ring is in tact and the washers are free of grooves and other damage. Order replacements for these parts if necessary when ordering the new gas cylinder.
Remove the cylinder. Spray a shot of aerosol lubricant over the exposed cylinder and tap on the sides to allow the oil to seep in between the cylinder and chair post. Wait two or three minutes for the oil to spread. Grip a pipe wrench around the body of the gas cylinder below the control attachment. Twist the gas cylinder to either or both sides to loosen it as you pull up. Gas cylinders fit snugly into the chair post. Removal may require strong force and repeated effort.
Measure the length of the gas cylinder's tubular body. Do not include the piston rod in your length measurement. Gas cylinders come in a standard width of nearly 1 1/8 inches that fits most manufacturer's chairs, so the length is the only consideration.
Reassemble the chair with the new gas cylinder. Push the cylinder body into the chair post with the pencil-shaped piston rod sticking up. Slip the rubber bumper on over the piston. Drop the hole of a bearing washer over the piston rod. The diameter of the hole in the washer will cause it to settle on the correct part of the piston rod post for supporting the bearings. Grease the bearing ring and place it on the piston over the washer. Put the other bearing washer on over the bearings. Put the chair base on over the post, replace the thin washer and slip on the clip.