Oxygen Inhaler Complete with Mask & Tube. The bag can be added as an extra at an additional cost. Oxygen is a compulsory piece of equipment for your practice Does yours need refilling or re-testing? Most health authorities insist on a product that will hold 340 litres of compressed oxygen that can be delivered at 10-15 litres per minute. That means the oxygen will last for approximately twenty minutes at 15 litres per minute If you already have a cylinder Medical World also offer a Refill and/or Retest service. Please call 0121 580 6600 for current costings and more information.