Office chairs use a gas cylinder to lower and raise the chair height. If you notice the chair lowers without moving the adjustment lever, it might be time to replace the gas cylinder. Removing a gas lift cylinder from a chair is basically the same regardless of the manufacturer. It is a good idea to protect the area around the chair when removing and replacing the gas cylinder because it has a thin film of lubricating grease around the outside.
Lower the chair fully and turn it upside down so the casters are facing up in the air. Lay some newspapers around the chair, especially if working over carpeting. There is grease around the lift cylinder and the newspaper helps to keep the grease from getting on the floor.
Insert a flathead screwdriver between the clip on the centre of the base. Twist the screwdriver handle to lift the upper half of the clip over the centre piston rod. Slide the clip away from the piston pin and set it aside.
Pull off the silver washer around the piston pin with your fingers and set it with the clip. Grab two of the caster legs and pull the caster base away from the gas cylinder and chair. Pull off the protective plastic sleeves around the cylinder, if your chair has the sleeve.
Spray silicone lubricant in the seam where the gas cylinder meets the chair base. The silicone lubricant helps loosen the fit. Do not spray the cylinder with the lubricant as it might cause the pipe wrench to slip.
Adjust the jaws of a pipe wrench around the base of the gas cylinder near the height adjustment lever. Twist the gas cylinder left to right with the pipe wrench while pulling up on the cylinder. If necessary, ask a friend to hold the seat steady as you remove the cylinder.
It is necessary to file the jaw marks on the gas cylinder body when reinstalling the same cylinder.
Avoid puncturing the cylinder with the pipe wrench if you plan on reusing the same cylinder. Punctures render the gas cylinder useless.