Chimney Pressure Testing in London
A chimney must be sufficiently sound and airtight to carry smoke and combustion gases safely from the fireplace or appliance to the outside.
A chimney pressure test – sometimes called a chimney integrity test – is used to investigate whether smoke or gases could escape through cracks, gaps or other defects in the flue.
H Firkins & Sons carries out chimney pressure and integrity testing throughout London, using the testing method most appropriate to the chimney and the problem being investigated.
Why would a chimney need a pressure test?
The purpose of an integrity test is to establish whether the chimney can safely contain the smoke and fumes travelling through it.
If the flue has cracks, gaps or other defects, combustion gases may escape into rooms, roof spaces or adjoining properties rather than travelling safely out through the chimney terminal.
A chimney pressure test can be particularly useful when:
- There is doubt about the integrity of an existing chimney or flue.
- Smoke or fumes appear to be escaping where they should not.
- A chimney has been unused for a long period and is being recommissioned.
- A property or chimney has undergone structural work or alteration.
- There has been a chimney fire or other event that may have damaged the flue.
- The fuel or appliance connected to the chimney is being changed.
- A more detailed chimney survey indicates that integrity testing is required.
How is a chimney pressure test carried out?
There is more than one way to test chimney integrity. The correct method depends on the construction of the chimney, its condition and what needs to be established.
Smoke integrity testing
Artificial smoke can be introduced into the chimney while openings are suitably controlled. The chimney can then be checked for evidence that smoke is escaping through defects or into neighbouring spaces.
Wöhler DP 600 pressure testing
Where appropriate, H Firkins & Sons can use a Wöhler DP 600 pressure-testing system.
The chimney is sealed and the equipment introduces air into the flue. The instrument measures the airflow required to maintain a specified pressure, providing objective information about the airtightness and integrity of the chimney.
Depending on the circumstances, one testing method may be sufficient or more than one method may be used.
Why does the chimney need to be clean?
A chimney should be clean before an accurate integrity test is undertaken.
Soot and deposits can temporarily fill small cracks or gaps and potentially disguise leakage. Cleaning the chimney first helps ensure that the test reflects the actual condition of the flue rather than the condition of accumulated deposits inside it.
For that reason, chimney sweeping may form part of the preparation for the test.
Should the chimney also have a CCTV inspection?
A pressure test tells us whether the chimney is retaining integrity, but it does not necessarily tell us exactly where a defect is located or what has caused it.
For this reason, a CCTV chimney inspection or comprehensive chimney survey may also be recommended.
Combining test results with internal camera images can provide a much clearer picture of both the presence and the likely location of a problem.
What happens after the test?
The results are recorded and we explain what they mean.
If the test indicates that the chimney is losing integrity, we can identify the appropriate next step. This might include further camera investigation, repair, relining or specialist assessment depending on the chimney and the defect found.
The aim is not simply to produce a pass or fail result, but to give you useful evidence on which to base the next decision.
Pressure Test or Comprehensive Chimney Survey?
A pressure test answers a relatively specific question: does the chimney retain sufficient integrity?
If you need a broader assessment of the entire chimney – including internal CCTV inspection, physical condition, smoke evacuation and other diagnostic checks – our Comprehensive Chimney & Flue Survey may be more appropriate.
For complex cases requiring detailed condition, measured performance and compliance assessment, see our CPC Chimney Inspection.
Chimney Pressure Test FAQs
What is a chimney pressure test?
A chimney pressure test assesses the integrity or airtightness of a chimney or flue to help establish whether smoke and combustion gases could escape through cracks, gaps or other defects.
Is a chimney pressure test the same as a smoke test?
Not necessarily. Artificial smoke can be used to investigate chimney integrity, while specialist pressure-testing equipment can measure leakage more objectively. The most appropriate method depends on the chimney and the issue being investigated.
What is a Wöhler DP 600?
The Wöhler DP 600 is specialist equipment used to pressure test a sealed chimney or flue. It measures the airflow required to maintain a specified pressure and helps assess the integrity of the system.
Does the chimney need sweeping before a pressure test?
Yes, the chimney needs to be sufficiently clean for an accurate test. Soot or deposits can fill small defects and potentially disguise leakage, so sweeping may be required beforehand.
Should I have a pressure test when changing fuel or appliance?
An integrity test can be particularly important where the fuel or appliance connected to an existing chimney is changing, because the suitability and condition of the flue need to be properly understood.
Will a pressure test tell you where the chimney is leaking?
It can establish whether the chimney is losing integrity, but identifying the precise defect may require a CCTV camera inspection or further investigation.
Book a Chimney Pressure Test
If you are concerned about the integrity of a chimney or need specialist testing before bringing it back into use, contact H Firkins & Sons to discuss a chimney pressure test.
We provide chimney pressure and integrity testing throughout London and surrounding areas.