Old boilers and gas appliances increase the risk of carbon monoxide poisoning, according to a report by the Gas Safety Trust.

The statistic was revealed in the Carbon Monoxide Trends Report, which provides an account of the trends relating to reportable CO incidents linked to natural gas usage in the UK between 1996 and 2010.

The report, commissioned by The Gas Safety Trust and part-funded by Local Authority Building Control (LABC), revealed that older gas appliances pose a greater risk of CO leaks. More than two-thirds of CO incidents reported involved central heating appliances, of which 50% were older boilers. However, there was no such trend in age-related incidents with space heaters.

The data also demonstrates the benefits of the introduction of new legislation. Regular non-condensing boilers have featured prominently in the reporting of CO incidents since 1996, whereas incidents involving  high-efficiency condensing boilers have been rare in the last six years since the Building Regulations were changed.

The report also highlights a worrying trend in terms of standards compliance. Since 1996 there has been a steady increase in the number of installations reported that were found not to comply with standards, suggesting that best practice is not being followed. This has become more apparent since 2001. According to the report, ventilation is the category where the most defects have been reported.

Evidence suggests that a greater number of CO incidents have tended to involve appliances for which no service contract is in place, as investigations have shown that a lack of servicing is the cause of most incidents.

Nigel Dumbrell, head of charitable operations for the Gas Safety Trust, said: “The involvement of older boilers in reportable CO incidents remains an issue. Older boilers can continue to operate safely for a significant time if serviced and maintained regularly. However, the report suggests that such servicing is not being done or that owners are waiting for them to cease operating before replacing them.”

The Gas Safety Trust is suggesting that an incentive to owners to encourage replacement would increase safety and promoting more efficient energy usage.

The report also highlights that unregistered operatives are still a problem, as the number of incidents reported involving them remains high.

Dumbrell added: “The effort to reduce and, ideally, eliminate the practice of unregistered gas operatives should be increased, as this would impact positively on the number of reportable CO incidents."