A letter published in this week's BMJ suggests that nearly 30 percent of anaesthetic machines in UK hospitals may not have the anti-hypoxia device which would prevent the accidental delivery of pure nitrous oxide to patients. Following the death of a child at Newham General Hospital in February 2001, Drs Saunders and Meek, specialist registrars in anaesthesia in the Northern Schools of Anaesthesia in Newcastle upon Tyne, surveyed a representative sample of 51 NHS hospitals in the UK . They discovered that many of these riskier machines, which are likely to be more than ten years old, are still in use, often located outside operating theatres in areas where they would be used infrequently or only in emergencies. The authors say that many responding hospitals may not meet the December 2002 deadline set by the Royal College of Anaesthetists for the replacement of outdated machines, thereby posing a continuing risk to patients, potentially at odds with Government policy on learning from adverse events.