Hospitals have been urged to check their oxygen equipment after a number of patients died because of errors.
The National Patient Safety Agency (NPSA) issued new oxygen safety guidance across England and Wales in light of 281 serious incidents reported to it between December 2004 and June this year.
Of these incidents, poor management of oxygen for patients caused nine deaths and may have contributed to a further 35.
Issues that commonly arose were the patient being given the wrong dose of oxygen, their oxygen blood concentration not being monitored properly, oxygen being confused with compressed air, empty cylinders and faulty and missing equipment.
Dr Kevin Cleary, NPSA's medical director, said: "Oxygen is one of the most common medicines given to thousands of patients each day across England and Wales and most is given safely.
"However, because of a lack of awareness, oxygen is often given without any prescription and patients are attached to oxygen tubing with no documentation of their medicine on their treatment chart.
"We have received reports of preventable incidents where oxygen cylinders were empty or patients were harmed when oxygen and air outlets were confused.
"Our recommended actions should make systems safer by reducing reliance on cylinders and reminding staff of the need to follow clinical guidelines in safe prescribing, administration and monitoring of patients on oxygen."