When it comes to portable oxygen therapy, there are two main options for delivery. These are portable oxygen cylinders which contain compressed oxygen gas, or oxygen concentrators, which use a battery powered system to compress and filter air, in order to create a consistent supply of concentrated oxygen.

In this post, AMS Composite Cylinders Technical Director, Tony Morrin, compares the two, looking at the pros and cons of each oxygen delivery system for NHS medical oxygen users in terms of patient autonomy.

Availability and duration of supply

One of the key considerations when specifying the right portable oxygen system for patients is availability and duration of oxygen supply.

Both solutions have their limitations. With a cylinder, the limitation is the finite supply of compressed oxygen in each cylinder. Once it runs out, it needs to be replaced. It is therefore important that there are robust delivery systems in place to ensure that the patient always has a sufficient supply of filled oxygen cylinders

The benefit of a concentrator is that it doesn’t require refilling – there is no need to replace cylinders when they run out, and there is a limitless supply of air. However, they do require a battery, which needs to be recharged regularly, meaning that the patient is dependent on having consistent access to a reliable power source.

Portable Oxygen Concentrator for medical oxygen

Portable Oxygen Concentrator

Consistency of oxygen purity

Oxygen purity is consistently higher when supplied from cylinders – it never drops below 99.6%, regardless of the flow rate required.

In battery-powered concentrators, purity is impacted by flow rate, and may be 90% or less, depending on the equipment.

Whilst oxygen concentrators can be useful for patients that require a lower flow of oxygen, cylinders provide higher concentrations that can be more suitable for patients with high flow requirements.

Weight and portability

For ambulatory oxygen, the overall weight and portability of oxygen systems are the primary considerations. Both systems require the patient to carry around equipment. For cylinders, this will include carrying a bag (and occasionally a trolley) and for portable oxygen concentrators this will include the bag, trolley and power charger.

Weight wise, portable oxygen concentrators can be comparable in weight, or sometimes, lighter than traditional aluminium cylinder systems. However, entire systems are significantly heavier than comparable composite cylinders.

The following table outlines some typical scenarios;

Lightweight composite O2 cylinder v POC

Lightweight composite O2 cylinder performance v oxygen concentrator

Currently, carbon composite cylinder systems provide a significantly better oxygen supply to weight ratio. In demand (pulse dose) conditions, a 2 litre carbon composite cylinder can provide 3-4 times the supply per kilogram of weight.

Lightweight carbon composite Oxygen cylinder

Lightweight carbon composite Oxygen cylinder

Battery technology is developing all the time, but currently, batteries will always limit oxygen delivery. They will have to improve significantly if they are to provide the same level of performance as comparable composite cylinders.

Safety and reliability

Oxygen always carries a safety risk. On one hand, should cylinders spring a leak, they can create an oxygen rich environment that could lead to an increase in fire risk. However, one of the benefits that cylinders have is that they are relatively simple – there are fewer things that can go wrong, making them more reliable and dependable.

Concentrator systems are more complex. The concentrators have many moving parts and electrical systems/batteries that can be subject to reliability issues. Should they go wrong, they are significantly harder and more expensive to fix.

In practical terms, the charging and battery components also pose additional safety concerns, including electrical and tripping hazards – something that is worth considering when specifying equipment for elderly patients.

Other considerations

When comparing overall lifecycle price, the two systems are fairly similar. The difference is that there are significant upfront costs to purchasing a portable oxygen concentrator, but lower running costs – using cylinders enables the purchaser to spread the cost over an extended period of time.

One minor downside of a portable oxygen concentrator is the noise – portable systems make a significant amount of noise during operation, which many patients find distracting. For those with hearing problems, this can pose serious problems when it comes to communication.


Ultimately, both systems have a key role in the delivery of portable oxygen therapy. It entirely depends on the circumstances and patient oxygen requirements as to which is more appropriate.

In terms of portability, composite cylinders still provide the most reliable solution, providing a significantly better oxygen to weight ratio, with less equipment to carry around, and lower initial investment. For many patients, a combination of both systems may be the best all-round solution.

Lightweight composite gas cylinders from AMS

Medical gas cylinder technology has advanced significantly over the past 5 years. Lightweight, non-limited life (NLL), composite cylinders have now entered the market, and will be an integral part of the development of new homecare treatments, portable oxygen therapies and medical gas applications over the coming years.

In portable oxygen therapy applications, these products provide significant benefits to patients, meeting the end user’s need for a lightweight cylinder that offers significant weight savings over aluminium cylinders and oxygen concentrators.

AMS Composite Cylinders is the exclusive continental European and UK distributor for an advanced range of lightweight, composite gas cylinders that are ideal for a wide range of healthcare, homecare, breathing gas and medical gas applications.

Our high-quality carbon composite cylinders offer high pressure (300 Bar), low weight, and NLL (Non-Limited Life) performance, and are accredited for use worldwide.

Further information about AMS Composite Cylinders Ltd can be found at www.ams-composites.com.