Does your office chair sink on its own? Causes and how to fix it without buying a new one

Usually because the gas lift has worn internal seals. Gas passes from one chamber to the other even when no one touches the lever, and the seat gradually sinks under the weight of the person sitting on it. In other cases, the gas lift is working properly and the fault lies with the lever that operates it.

The gas lift is a sealed steel cylinder containing pressurised nitrogen, with a valve at its upper end. Pulling the lever presses the valve button: the gas flows between the two chambers and the seat rises or lowers. When the lever is released, the valve closes and the height locks in place.

The most common reasons why a chair loses height are:

Worn gas lift seals

Over time, they no longer separate the chambers properly, causing the chair to lower slowly while someone is sitting on it.

Valve not closing fully

Wear prevents it from sealing properly, so the seat does not remain at the set height.

Lever or mechanism pressing the valve

A bent lever, a loose mechanism screw or an incorrectly tensioned cable can keep the button pressed without anyone touching it.

A gas lift that is not durable enough for its intended use

In intensive-use or shift-based workstations, a gas lift with a low resistance rating will reach the end of its service life sooner.

Impacts and misuse

Dropping heavily onto the seat or standing on the chair subjects the gas lift to sudden loads.

In an office, it is worth looking beyond the chair that is failing. If the others are the same model and were purchased at the same time, their gas lifts have been in use for the same number of years.

Simply observe how the chair moves. If it lowers slowly while you are sitting on it, the gas lift is faulty. If it rises by itself when you stand up and drops suddenly when you sit down, the valve is open, so check the lever first, as it may be repairable without replacing the gas lift.

To check it yourself:

1. Stand up and release the lever

It should return to its resting position on its own. If it remains raised or is stiff, that is where the problem starts.

2. With no one sitting on the chair, pull the lever

The seat should rise to its highest position. If it does not, the gas lift lacks pressure or the lever is not reaching the button.

3. Sit down without touching anything

If, after a while or by the end of the working day, the seat is lower, the gas lift seals are worn.

Make a note of what you have observed. With this description and a few photos, we can provide an approximate quotation before moving the chair.

Only if the fault lies with the lever or mechanism: these can be adjusted or replaced while retaining the gas lift. If the seals are faulty, there is no reliable repair, as the gas lift is a pressurised gas cylinder that is not designed to be opened. The entire unit must be replaced.

You should not attempt to repair it yourself either: the gas lift must not be dismantled, drilled or cut.

It is worthwhile when the frame is sound and the chair is of professional quality. Replacing the gas lift restores height adjustment for less than the cost of an equivalent new chair., while everything else remains fully functional: the frame, mechanism, backrest and base.

The part is not expensive: in our catalogue, a replacement gas lift for office chair costs between €19.50 and €39 excluding VAT. The repair quotation includes the part and labour, and we provide it before starting. If the repair is not cost-effective, we will let you know. For these cases, we offer refurbished task chairs from €69 per unit, excluding VAT.

Repairing also helps prevent waste. The Waste and Contaminated Soil for a Circular Economy Act 7/2022 places prevention at the top of the waste hierarchy and defines it as including ‘extending the useful life of products’. In the environmental product declaration for the New Aeron by Herman Miller (2016), 83 of the 87 kg CO₂e generated over its life cycle are attributable to raw material production. Most of the chair’s carbon footprint comes from manufacturing it, and replacing the gas lift preserves everything else.

At our facilities in Illescas (Toledo), we first confirm that the gas lift is faulty, fit a new one in the correct size for your chair and inspect the rest of the chair before returning it. Each unit goes through five steps:

Which gas lift do we fit?

For a repair, a new gas lift in the correct size for your model: either an original branded part or a compatible alternative. The relevant European standard for these gas lifts is EN 16955:2017 —in Spain, UNE-EN 16955—, which in Germany replaced the DIN 4550. It specifies the strength and durability tests for the gas lift's tapered tube and includes guidance on selecting the appropriate strength class.

For our refurbished chairs, whenever the original gas lift is not in perfect condition, we fit a new Class 4 gas lift (DIN 4550) with a 2.5 mm outer tube. This principle applies throughout our entire process, Segunda Vida by Factoryoficina: anything in perfect condition is inspected and retained; anything that is not is replaced.

What warranty does the repair include?

The repair comes with a 6-month warranty. Any new parts we fit, such as the gas lift, also come with their own warranty, which varies by product. If the work does not involve any new parts—for example, welding—the repair warranty applies: 6 months.

It depends on the number of chairs and their location. In Madrid and Toledo, we collect four or more chairs free of charge. In all other cases, you are responsible for return transport costs. You can also bring them to our facilities in Illescas (Toledo) at no cost.

How our office chair repair serviceworks:

At Factoryoficina, with 26 years of experience in the sector, we repair task, ergonomic, executive and visitor chairs from numerous brands for businesses and private customers throughout Spain. We also handle batch repairs for businesses, inspecting every chair of the same model to maintain a consistent office appearance and, subject to availability, providing loan chairs while repairs are carried out.

If you have several chairs of the same model showing the same symptoms, group them together: in Madrid and Toledo, collection is free for four or more chairs.

If the chair is already coming to our workshop for a gas lift replacement, you can take the opportunity to have it fully refurbished with our chair reupholstery and reupholstered service. It will be returned repaired and newly upholstered, all in a single visit.