Leaky ductwork is paid for twice: once to install, then forever in fan energy pushing air that never arrives. Gemini AMPM pressure tests ductwork to DW/143, the BESA method for air leakage testing, proving your system meets the leakage class the specification demands. Fail, and we find and fix the leaks too.
DW/143 is the BESA method for ductwork air leakage testing, and the procedure is pleasingly blunt. Seal the section under test, connect the rig, bring the duct to its specified static pressure and measure exactly how much air escapes. The result is compared against the leakage class the system was built to — classes defined in DW/144 and in BS EN 1507 and BS EN 12237 for rectangular and circular duct respectively.
High-pressure ductwork must be tested — DW/144 makes that mandatory — while medium and low pressure systems are tested where the specification calls for it, typically on a sampling basis. We test new installations for practical completion, refurbished systems after alteration, and older systems where energy bills or airflow complaints suggest the ductwork is quietly giving air away.
A failed test is information, not a verdict. We locate the leaks — smoke tracing and close visual inspection along joints, seams and access fittings — then seal them with the right remedy for the failure: sealant systems for joints and seams, mechanical repair where the metal itself has failed. Then we retest, because a repair without a retest is an opinion.
The stakes are bigger than the certificate. Leaking supply ductwork means fans working harder and energy bills paying for air that never reaches a room; leaking extract can pull contaminated air back into voids and ceilings. Where leakage hints at wider internal problems, a ductwork CCTV survey shows exactly what is happening inside the run. Test, see, fix — in that order.
DW/143 is the BESA practical guide to ductwork air leakage testing — the standard UK method. A test rig pressurises an isolated section of duct to a set static pressure and measures the leakage rate, which is then judged against the leakage class the ductwork was specified to under DW/144. It is the companion to DW/144, the construction specification: one says how ductwork should be built, the other proves how well it was.
No. DW/144 makes testing mandatory for high-pressure ductwork, while low and medium pressure systems are tested when the project specification requires it — commonly a sample percentage chosen by the designer. Specifiers increasingly test more than the minimum because leakage is energy, and airtightness targets have tightened. If you are unsure what your specification demands, send it over and we will tell you what needs testing and what does not.
Usually less dramatic than it sounds. Most failures trace to a handful of poorly made joints, missing sealant runs or damaged flexible connections, and most are sealed and retested within the same visit or shortly after. The report shows the measured leakage, the allowable figure and the shortfall, so everyone can see the size of the problem. What matters is the retest certificate at the end — that is the document with value.
A named engineer, not a call centre, comes back within 24 hours. Tell us the building and what you’re dealing with, and we’ll scope it properly.