In medical gas cylinders – ensuring the quality of the gas inside can be a matter of life or death.

Contamination of the gases inside can lead to serious problems. In addition to causing corrosion inside the cylinder, contamination can render the gas inside useless, or in the worst cases, harmful. It’s vital that cylinder manufacturers, gas companies, medical oxygen providers and patients take steps to prevent that happening.

One of the easiest ways of preventing contamination is by fitting cylinders with valves incorporating residual pressure devices (RPD). At AMS Composite Cylinders, we encourage the use of valves fitted with RPDs in all medical gas cylinders – and it’s a prerequisite for certifying it for 10-year re-testing.

As part of our work on Technical Sub Committee 7 – Medical Gases, for the British Compressed Gases Association (BCGA), our team was involved in the creation of Guidance Note 31 – The Use of Valves Incorporating Residual Pressure Devices.

You can download the report in its entirety here.

Guidance Note 31 – An Overview

The technical document provides guidelines for the selection, installation and use of valves with RPDs in medical gas cylinders.

It covers:

  • The benefits of valves fitted with RPDs
  • The specification of valves fitted with RPDs, including testing requirements
  • Testing regimes for the medical cylinder package
  • Valve selection and verification
  • Valve changeover
  • Filling equipment design reviews
  • Risk management

How Residual Pressure Devices Work

Medical gas cylinders are designed to safely contain a gas under pressure. Cylinders are closed and sealed by the valve – and an RPD adds an extra layer of protection to the package.

Valves fitted with an RPD are designed to maintain a nominal positive pressure inside the cylinder. This prevents the gas cylinder from being completely emptied during use, and stops atmospheric contamination, even if the vale operating mechanism is left open. It also reduces the risk of backflow contamination from downstream devices.

The benefits include:

  • Maintaining gas quality between fills
  • Protecting the internal condition of the medical gas cylinder throughout its service life
  • Stopping water ingress and preventing atmospheric contaminants from entering the cylinder
  • Preventing internal corrosion and subsequent particulate contamination of the gas
  • Improving cylinder filling efficiency
  • Delivering anti-fill protection to stop the illicit filling of a cylinder

Recommendations for Medical Gas Cylinders

The core recommendation set out in Guidance Note 31 is that wherever possible, all valves fitted to medical gas cylinders should incorporate a residual pressure device, and a non-return valve.

For existing cylinder packages, when valves are replaced, they should be replaced with a valve fitted with an RPD (a variation may be needed to update the Marketing Authorisation)

In addition, when adding a new cylinder package to the Marketing Authorisation, it should be supplied with a valve fitted with an RPD.

Medical Oxygen Cylinders from AMS Composite Cylinders

AMS Composite Cylinders supplies state of the art, lightweight gas cylinders for a wide range of healthcare, homecare, breathing gas and medical gas applications.

We supply clients across the UK, Europe, the Middle East and Latin America, providing industry leading quality, reliable service and short lead times.

Producing cylinders to a wide range of recognised global standards, we hold accreditations in all major markets worldwide. We manufacture to ISO and EN standards (including ISO-11119-2, ISO 11119-1, EN 12245, EN 12257, ISO 7666, ISO 11118 and EN12245) and to the requirements of UN PED/TPED, DOT (USA) and TC (Canada).


For additional information AMS Composite Cylinders, our medical gas cylinders and our accreditations, please contact us today.