https://click4r.com/posts/g/18....780956/a-how-to-guid
Why It Is Important To Have An Annual Gas Safety Check Gas Safe engineers must inspect the flues and gas appliances annually. This includes appliances that are shared, like boilers. During the inspection the engineer will inspect the flue and, if needed, remove it. The engineer will also test each appliance for carbon monoxide. The engineer will disconnect the appliance if it's considered to be "Immediately Dangerous". This issue must be resolved before the appliance can be used