As of 1st January 2013, all rented properties that have a gas central heating boiler flue that has either been fitted hidden in the ceiling space or fitted away from an external wall must now be fitted with an inspection hatch. If your boiler is situated on an outside wall it is unlikely that you have this type of flue and if you can see the entire flue it will not affect you, your gas engineer will be able to tell you.
All gas engineers must now be able to inspect the whole length of the flue, in line with industry guidance. If they are unable to fully inspect the flue it must be deemed at ‘At Risk’ (recommending to not use)and the engineer will ask for consent to turn it off. You are within your rights to refuse permission for it to be turned off; however you will be asked to sign paperwork to confirm you accept responsibility for those defects identified in the system – which would be the possible leak of carbon monoxide escaping unnoticed from the concealed flue into the property.
You may be able to go back to the builder if it is less than two years and look to the home warrantee if less than 10 years.
What it does mean is the gas engineer will not be able to provide a Gas Safety Certificate until an inspection hatch has been fitted and they have inspected the whole flue and as a landlord you must by law have a Gas Safety Certificate in place to rent a property out and this must be renewed every year.