Flue integrity and spillage testing: why they matter

Practical notes on flue integrity and spillage testing

• Spillage testing checks combustion gases are not entering the room
• Flue flow testing confirms adequate draw for the appliance
• Open-flued appliances need this checking more closely than room-sealed ones
• A failed test means the appliance should not be left in use
• Testing is part of every gas safety check on a suitable appliance

The engineering behind flue integrity and spillage testing

Spillage testing checks whether combustion gases are escaping into the room instead of travelling up the flue, using a smoke match or similar indicator at the draught diverter. Flue flow testing confirms there is adequate draw for the appliance type. Both are especially important on open-flued appliances, where a blocked or poorly performing flue can allow products of combustion into occupied space rather than to outside air.

Where we deal with this

• Melksham (SN12) · 12 mi
• Bear Flat (BA2) · 8 mi
• Wells (BA5) · 10 mi

Questions we get asked

What is an open-flued appliance?

One that draws combustion air from the room it is installed in rather than being sealed from it, which makes flue performance more critical to occupant safety.

Can a blocked flue be hard to spot?

Yes — blockages such as bird nests or debris are not always visible from inside, which is why the physical test matters more than a visual check alone.