Flow Rate Testing of Ventilation

Air Leakage Testing Ltd undertakes air flow measurements of domestic ventilation for Approved Document F requirements. 

Ventilation is key in controlling moisture and pollutant levels in any building, if the ventilation is not sufficient it can lead to an unpleasant living environment and in the longer-term problems with the building and/or health issues.

Although extract vents claim a level of air flow based on laboratory testing this does not guarantee they will achieve this in practice due to various issues but most commonly the installation. Therefore, Approved Document F (Ventilation) requires background ventilation to be tested after installation.

The requirements apply to extract ventilation in bathrooms, kitchens, toilets and utility rooms and/or mechanical ventilation in other habitable rooms in new buildings, conversions and extensions.

Air Leakage Testing Ltd undertake the flow rate measurements using UKAS accredited equipment to determine whether each vent and the overall system complies with the requirements of Part F, including producing a test certificate for each property that includes all the information required for compliance with Part 3 (Commissioning Details) of the Completion Checklist and Commissioning Sheet.


Different vents are required to achieve different levels depending upon the type of ‘System’ and the purpose of the room.



Background ventilators with intermittent extractors, these are the extract vents that come on with the light in the bathroom or when the cooker hood is switched on, they are used in combination with trickle vents in windows/doors.

Vents over the kitchen hob or in the utility room need to achieve 30l/s, bathrooms 15l/s, toilets 6l/s.

Continuous mechanical ventilation, these are the vents run at a ‘trickle’ all the time in bathrooms, kitchens, toilet, utility, etc but can run at a boosted level when required.

There are required flow rates for boost in the wet areas and an overall rate based on bedroom numbers.

Continuous mechanical ventilation with heat recovery. This is where there are air supply vents in every room and also extract vents in the ‘wet’ areas.

There are requirements for individual fans on boost, a whole ventilation rate on trickle and a need for supply and extract to be balanced.

Our vent Testing Process

The ventilation testing is carried out using a hood/cone placed over the extraction fan which channels the air from fan through a calibrated anemometer which measures the air flow.

A certificate including the information required for Part 3 of the Part F completion checklist is produced for each property (listing the air flow results against the requirements for each fan and the overall system (where required).

The testing is best completed in combination with air or sound testing to minimise the costs.

What our clients say about us

“ALT were extremely helpful and knowledgeable. They worked with the site team to identify and resolve issues during construction.”
“I have used Air Leakage Testing Ltd on two separate occasions at my property and found them to be extremely thorough and professional at all times. The turnaround between site visit and subsequent reports was quick and efficient - making my life a whole lot easier! Would highly recommend to anyone!”

Established in 2002

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Why choose alt?

Helpful Engineers

We work with you to achieve the best result, identifying potential issues and repeating the testing once these have been addressed. We are on hand to answer any questions before, during and after the testing.

Flexible & Responsive

We aim to fit in with your chosen dates and times, to work around other trades and to minimise on-site disruption. Our lead times are typically a week but it may be possible to fit you in sooner. We issue quotes and certificates within 1 working day.


We have been air testing since 2002 and keep pace with changing regulations. All our test engineers hold ATTMA L1 registration and have considerable experience in undertaking tests and resolving potential issues.

Great value

Our efficient processes help us to offer very competitive prices. In addition, we can undertake air and sound testing on the same visit to save you more money. If you do receive a cheaper air testing quote, we will beat it.

Get a quote

Complete a few details about your project and we will provide an estimated cost. Provide more information and we will issue a formal quotation.