If you’ve assembled an office chair, you’ve no doubt seen one of these cylinders. The bottom goes into the wheelbase, the top inserts beneath the seat, and then you can magically raise or lower the seat to a comfortable height with just the flick of a lever, handle or paddle.
Most modern ergonomic office chairs come with these pneumatic cylinders. The “gas” is actually compressed air. And most of the time, they work flawlessly. Especially if you bought your chair from a reputable company.
But if you want to know more about how your height adjustable chair actually works, or what to do if your gas cylinder fails and needs to be replaced, you may find this guide helpful.
What is a gas cylinder?
A gas cylinder, also called a pneumatic cylinder or gas lift, is the unit that allows you to raise or lower your office chair with the use of a lever below the side of the seat.
Unlike older chair models that used a threaded spindle lift, where you had to turn the chair counter-clockwise to raise and clockwise to lowe the chair, a gas lift chair uses a chamber with compressed air to change the height of a chair.
Also called a spring, this chamber mechanism makes it quick and easy to adjust the chair relative to your desk height, so easily find a comfortable and ergonomic sitting position.
How does a pneumatic cylinder work?
As mentioned, a gas cylinder relies on compressed air to raise and lower your seat.
When the lever on your chair is engaged, it activates the cylinder. If you engage the lever and while releasing your weight from the seat, the air in the cylinder compresses and pushes the piston out of the air chamber, thereby raising your seat.
With the piston pushed out, the air in the chamber is expanded, allowing the seat to be lowered when you activate the lever and push down with y our weight on the seat.
Parts of a Gas Cylinder
Standard pneumatic chair cylinders are composed of the following parts:
The Stand Pipe (aka outer column): This is a 2” diameter main column that connects to the chairs’ five-star base. The bottom of the column in tapered. This is the end you insert into the wheelbase when assembling an office chair. The length of the column and tapered section may vary from model to model, but the 2” diameter for the main column is standard with most cylinders.
Piston (aka inner column): The 1.1 inch diameter piston that connects to the seat base and raises or lowers to adjust the chair height. The end of this unit is also tapered to fit into the hole in the seat base unit (also known as the swivel unit). The top of the piston on a new cylinder has a plastic cover. You will remove that when installing to expose the button at the top (aka the actuator).
Actuator: The button at the top of the piston that gets pushed and activates the cylinder to raise or lower the chair.
Dust Cover: The telescoping plastic dust protector placed over the main column.
Retainer Clip: The little clip at the bottom of the piston column that keeps it from sliding out of the main column.
Replacing a gas cylinder
If you’re reading an article about gas cylinders, there’s a good chance you’re here because you actually need to replace one.
Luckily, whether your chair came with a faulty cylinder, you need more “travel” and height, or your faithful pneumatic chair is no longer “pneumatic” after all these years, it’s actually pretty simple to replace a gas cylinder.
The first step is to figure out what size you need.
Gas Cylinder Sizes
As mentioned above, most cylinders come with standard diameter measurements for the stand pipe and piston.
So, before you start looking at new cylinders, first confirm that your current cylinder has the standard 2” diameter at the base of the main column. See the image above for an illustration of this measurement.
**Do not include the plastic cover in this measurement.
Also check to see that you have a standard 1.1” diameter piston.
Once you’ve confirmed that you’ll be able to use a standard diameter cylinder replacement, you’ll then need to figure out how much “travel” you want.
What’s your stroke (aka travel)?
If you’ve read many chair spec sheets (doesn’t everyone spend their time reading chair spec sheets?) you might’ve seen the terms “stroke” and/or “travel” in reference to the chair cylinder.
This simply means that the cylinder will raise or lower the chair within a certain number of inches. For example, a 4 stroke chair cylinder is quite common, meaning the chair can be raised or lowered within a range of 4 inches.
The easiest way to determine the stroke of your current chair/cylinder is to do a quick measurement:
- Raise your chair up to it’s highest point. Now measure the height from the floor to the seat.
- Lower your chair down to the lowest and take the same measurement.
- The difference between the highest and lowest point is your travel or stroke.
As mentioned, you’ll find that 4” is a pretty common travel for chairs, but this number can range from as low as 3” all the way up to 10”.
What travel range is best for you will depend on your height, the height of the chair, and the height of your desk(s). For example, if you need more chair height for a taller desk setup, you can find a replacement cylinder with a longer piston and therefore more travel than your current cylinder offers.
Another important consideration when it comes to gas cylinders is the weight capacity.
Most chairs come with a stated maximum load capacity. For example, many big and tall office chairs can hold over 400 lbs, while standard ergonomic task chairs might be closer to 250 lbs.
If weight capacity of the chair frame is important, make sure your replacement cylinder is also up to the task.
For example, standard cylinders can adjust with a capacity up to 250 lbs. But “heavy duty” class 4 pneumatic devices can handle over 450 lbs (this would be necessary on a chair that qualifies for ANSI/BIFMA large occupant standards).
Bottom line: Make sure you get the right class cylinder that’s consistent with your chair’s weight capacity limits.
Final note: Also be sure to check if the cylinder is rotating or non-rotating to match the needs of your chair.
Removing the Old Cylinder
Now comes the fun part. Just kidding, this can actually be kind of a pain. But if you want to revive your trusty old office chair with a fresh new cylinder, you’ll need to take that old one out first.
You can try this method (explained in the video) or keep reading for simple basic steps that we’ve used in the past:
Remove the tapered end from the wheelbase.
First, tip your chair over so you can access the wheelbase. Then, with a hammer or rubber mallet, start tapping around the edge of the tapered bottom of the cylinder.
Try not to hit dead center where the retainer clip is. Keep tapping around the edges to loosen the unit so you can pull the column from the base.
If you can’t get it free, some people suggest using a flat head screwdriver to remove the retainer clip from the bottom.
This will release the piston from the cylinder. Now you’ll just have a wheelbase with the empty cylinder column stuck in it.
In this case, you should be able to turn the wheelbase upside down and hammer the tapered end of the column through until it’s free.
Remove the piston from the seat base.
Next, you’ll have to remove the piston head from the seat base. To do this, tap around the edge of the top of the piston with a rubber mallet to loosen it. You can use WD 40 to make this easier.
Once it’s a little loose, you should be able to wiggle it free from the seat base.
Find a Replacement
The final step is to go online, find a replacement cylinder, and insert it back into your wheelbase and seat. Again, if you’ve confirmed that your cylinder is a standard diameter, this part should be pretty easy.
You can even find a bunch of standard replacement gas chair cylinders on Amazon.
But if you have any questions or need a specific size cylinder or more obscure unit for your chair, we recommend dealing with a chair parts specialist.
Here are some good places to look online:
Hopefully, this primer on gas cylinders will help you appreciate this all important component of your height-adjustable office or gaming chair.
And if you need a new one, you’ll know just what to do.