Open-flued spillage test: an ordered method

A spillage test checks whether an operating open-flued appliance clears its combustion products through the flue instead of releasing them into the room. It follows a satisfactory flue-flow check; the two tests answer different questions.

Use the appliance’s prescribed method and the applicable procedure. The heat setting, warm-up period, smoke position and any permitted repeat are specific to that test. A generic five-minute wait or an improvised smoke position can give a misleading result.

1. Confirm the flue and air supply are suitable and that the preceding checks are satisfactory.
2. Set the appliance and room conditions as required. Leave permanent ventilation unobstructed.
3. Run the appliance at the specified setting for the prescribed period, then observe smoke at the specified test point.
4. Test the relevant combinations of extract fans, other equipment and internal doors to find the conditions that most adversely affect the appliance. Fans in adjoining rooms can matter too.
5. Judge the smoke behaviour against the procedure. Use only its permitted repeat or additional warm-up; do not keep extending the test until a failure appears to pass.
6. Record the conditions and result. If the test fails, make the appliance safe under the unsafe-situations procedure, investigate and rectify the cause, then repeat the required checks.

A draught diverter moderates the effect of flue draught on the burner; it does not make spillage harmless. A blocked flue, insufficient air or fan-induced depressurisation can prevent safe removal of products. Do not leave a failed appliance in use.