Computer chair Gas Cylinder Replacement

What kind of office chair? If it's a quality chair manufactured by Herman Miller, it should be covered under warranty.

I have an office chair made by Gobal. It comes with life time warranty. The cylinder failed after 10 years of use. Called them, and they said cylinder warranty is 10 years, and I am out of luck. Anyway, I manage to fix the problem. I think the air seal inside the cylinder dried up after a long usage. I just tilt the chair side ways so the cylinder is the a horizontal position so that the lubricant inside the cylinder flows to seal. The fix will last for a while and I have to do it again from time to time.

I think the correct term is a gas strut and there are lots of places you can get them online as well as advice on how to change them.

I have tried several times to detach a cylinder from a chair and replace in another one, different brand name. It seems the hole size is standard. You can take a good cylinder from a broken chair and replace it for your wanted chair. Use a big hammer and kick it out slowly. Put a wooden piece on to protect the surface. I got a very good Global chair, may be 25 years ago, with a broken cylinder and replace it with a Staples chair cylinder. Later I remove that and replace with another higher cylinder. So I think there are good chances that you can find a good cylinder that can fit your chair.