Pneumatic chairs, commonly used as office furniture, use a lift to allow height adjustments. With everyday use, the lift and screws can loosen, usually resulting in a seat that will not stay in place. You can buy new parts or hire a professional to repair this problem, but because they can cost nearly as much as a new chair, it is not always a good idea.
For a less expensive and far simpler option, use the following tips to keep your chair in working condition.
Use a screwdriver or socket wrench to remove the screws connecting the seat, arms and back to the frame of the chair. Put a strong adhesive on the threads of each screw, and then reinsert them. Allow them to dry before sitting in the chair.
Fix a sinking seat by pulling it to the level you desire, and mark it on the cylinder. Measure the distance from your mark to the base. Now, cut an unused yardstick and place the pieces between the part of the frame that holds the wheels and casters and beneath the seat. Hold them in place by wrapping them with duct tape.
Ensure the wheels are in good condition by flipping the chair over and checking for wear and tear. To replace wheels and casters, pull or unscrew the wheels and use a screwdriver to pry the casters out of the frame. Clean out any debris. Purchase new wheels and casters from any home improvement store. If you can't find the exact size you need, drill a hole to create a bigger hole or insert a dowel rod drilled to the caster's size. With a rubber mallet, hammer the dowel into the holes. Now, insert or screw the new casters and wheels into place.