Smoke Shaft & Plenum Testing

What we do

In addition to standard air testing for buildings, Air Leakage Testing undertakes a wide range of additional types of testing to establish air permeability for purposes other than energy efficiency.  Amongst the most common are:

  • Smoke shaft testing for Automatic Opening Ventilation (AOV)
  • Plenum and Raised Access Flooring (RAF) testing to BG65

Smoke Shaft Testing

We undertake smoke shaft integrity testing to confirm that the shaft is sufficiently air tight to allow the automatic opening ventilation to perform as required when it is fitted and commissioned.

Our test engineers have experience of air tightness testing builders shafts of all sizes and construction so, should the worst occur and the air permeability target is not achieved at the first time of asking, they can use smoke to identify the leakage paths and use their knowledge to advise on the best solutions.


The automatic-opening vents are a key part of the fire strategy for multi-storey buildings to extract smoke in the case of a fire. For the fans and vents to perform as required the shaft itself must be sufficiently air tight that they can create the pressure difference to draw smoke out of the building and protect the occupants and/or emergency services.

We work to air permeability targets set by the automatic-opening ventilation manufacturers that allows their equipment to operate effectively.

How it Works

An air pressure test is conducted using a fan installed into the shaft. The intended openings of the shaft (i.e. extract point and openings for ventilation grilles on each floor) are sealed off for the test so that the integrity of the shaft itself can be determined.

The test takes place in advance of the automatic-opening ventilation equipment being installed and commissioned.

There is a great deal of variety in the smoke shafts and therefore the best way to seal off the louvre openings and cap the shaft but our test engineer will talk site through the best way for the shaft to be prepared and how best we can set up our equipment.

Plenum & Raised Access Flooring Testing

Raised Access Floors (RAFs) are often used to create Plenums as part of the ventilation strategy for a building. In these instances, it is important that the plenum and RAF provide sufficient air tightness to allow the air supply system to provide the necessary air flow/air changes.


The specific requirements may vary for each building but typically Plenums need to achieve under 0.7 l/s/m2 of floor area at a 50Pa pressure difference and the Raised Access Floor (RAF) should be under 1.1 l/s/m2 of floor area at a 50Pa pressure difference.

How it Works

The testing requires a fair amount of preparation on the part of the contractor as the air permeability of the plenum and Raised Access Floor (RAF) are determined separately. This means that the RAF is fully sealed and a test is conducted on the plenum, ahead of most of the taping being removed so that a second test can be conducted to calculate the air leakage through the RAF.

Buildings, RAFs and circumstances are different so our experienced engineers will guide you through the preferred way to seal up the floor.

Should the plenum and/or RAF not achieve their targets then we can use air and smoke to identify the leakage paths.

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7 Lawson Way, Aylesbury, Buckinghamshire, HP18 0UW

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