By Nick Triggle
Health reporter, BBC News
The NPSA is concerned about standards in hospitals
Concerns are being raised that patients receiving oxygen treatment are being put at unnecessary risk because of poor monitoring and faulty equipment.
The National Patient Safety Agency has given hospitals in England and Wales until the end of March to improve.
The watchdog said it was acting after receiving reports of people dying and being seriously harmed due to problems.
Experts said despite over 2m people getting oxygen treatment each year, it was still not being prioritised enough.
The therapy is given to a range of patients, including people with lung problems, trauma patients and those struggling with serious infections.