Flue Integrity Testing in London and Kent Covering Orpington, Sevenoaks, Petts Wood, Streatham, Tooting, Fulham and surrounding areas This process is one of the most essential. By law, every working solid fuel fire and Class 1 gas fire must have a flue in good working order. Integrity testing is our method of establishing if your flue meets the lawful requirements. Our integrity test is carried out by a fully trained member of our team and consists of the following; A smoke pellet is lit and the resulting smoke is introduced into the chimney. Once the smoke has began to exit the tested flue the fitter will then cap off the designated terminal at roof level, which in turn will allow the required flue to be completely filled with smoke. The flue run is then monitored to ensure that smoke does not escape into the building or neighboring flues. The integrity test can only be passed and signed off if the smoke exits from one terminal. If smoke escapes from the tested flue then the integrity test has failed.