Chimney lining specialist in the Royal Tunbridge Wells area
07516 017341
01892 319315
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01892 319315
We are Hetas Registered Installers

Passing The Legal Tests

Rods and brushes test

A general test with rods and brushes before the actual sweeping makes sure all of the flue can be swept and cleans the chimney ready for subsequent other testing. Make sure a professional who is HETAS registered or a member of the Guild of Master Sweeps does the test. It will help him or her know what kind of rods and brushes to use, to ensure your flue is properly cleaned. This advance test, using the feel of the rods, looks out for large soot blocks and other deposits which will help your sweep plan in advance. A certified and professional sweep should give a certificate with a verdict on the situation of your chimney flue and what actions are needed.

Core ball testing is discussed in the Flexi Stainless Steel Liner section of this website. Another test is the ‘Air Tightness’ procedure. Flues should always be airtight, if possible. Leaks can let cool air in and make the flue gas temperature go down. Soot and tar deposits can then build up and there might be acid condensation. Fumes could then carry into the home giving a higher risk of lethal CO poisoning.

Air tightness testing follows British Standards within a set procedure:-

  • At the time of the test, the appliance must be alight.
  • The chimney flue must be warmed up 10 minutes or longer before the test with a single burner camping gas stove or blowtorch.
  • Loss of smoke should be prevented by taping the fire opening to close it, using paper, polythene and masking tape.
  • Smoke pellets should be used in the flue to create smoke.
  • Seal any smoke coming from the chimney pot with a polythene bag or closed cell foam bungs over the pot and fixed with masking tape.

Hetas Approved Installers

A professional examination will then be made of the chimney breast and stack, nearby walls at all levels of your property including the attic and roof – looking out for smoke leaks when the bag or bung is taken from the chimney pot. Less smoke than anticipated may indicate a non-visible leak so the test should be repeated until the fault is found. Also, outside air breezes could easily waft smoke away quickly and daylight can block the visual inspection. Smoke leaks can be found some distance from any fault so look out for that.

Tests typically last five minutes and your chimney sweep should advise about any flue faults found that need repairs.


Legal tests on your chimney by TLC Stoves and Liners.