Why is my safe boiler suddenly unsafe?

I have had HomeCare cover with British Gas since 2004. Each year, engineers have checked the boiler in my rented-out property and passed it as safe. However, in February, their engineer issued a safety warning, saying the boiler could put my property, and even life, at risk. Apparently, this was because it was fitted to a "sealed system". I wrote to British Gas and asked why it had previously passed my boiler as safe, when it was now deemed unsafe, and was told the engineer had made a mistake. When I called the manufacturer, Potterton, it confirmed the engineer was correct and that the boiler should be treated immediately as dangerous. British Gas then said Potterton was wrong, and refuses to discuss the matter, except it is very keen to try to sell me a new boiler. I have received a number of sales calls since the report. I have paid the company hundreds of pounds over the last six years to ensure the safety of my property and tenants and it has failed to do so, and now will not take responsibility for this failure. What do you suggest? JB, Oxford We contacted Gas Safe Register, which told us that, as far back as 2005, this type of boiler was considered "not approved" for a sealed heating system, like the one you have. Back then, the "gas industry unsafe situations procedure" provided guidance to registered engineers that they should classify as "at risk" appliances fitted to, but not approved for, a sealed heating system. Indeed, this is the procedure the engineer who serviced the boiler this year correctly followed. When we investigated, British Gas told us this issue was raised with the tenants at the 2009 inspection but clearly this had not been passed on to you. The company has said it is now working with Gas Safe Register to ensure guidance across the industry is clearer, reducing the need for engineers to make a judgment which can lead to differing risk classifications. It stresses that neither you, nor your tenants, were left unsafe at any time, and that safety of customers remains its first priority. It has apologised for any concern caused and, after much negotiation, offered to refund £456, which is equivalent to four years of HomeCare payments. We welcome letters but cannot answer individually. Email us at [email protected] or write to Bachelor & Brignall, Money, The Guardian, 90 York Way, London N1 9GU. Please include a daytime phone number