Plenum Testing

Do you have plenums in your building? If the answer is yes, you need to be aware that a staggering 70% (approximately) fail their first air test. HRS have years of experience of raised access floor plenum air pressure testing and can work with you to ensure you pass your air test first time.

HRS can ensure that an air test site advice visit is arranged as soon as the floor is in place, we can then assess your design and offer you specification advice to ensure that your plenums are adequately sealed.

What is a Plenum?

A plenum is part of a building that normally facilitates air circulation for heating and air conditioning systems by providing pathways for either heated/conditioned or return airflows, usually at greater than atmospheric pressure. Typically this is under a raised floor or between the structural ceiling and the suspended ceiling.

Why do 70% (approximately) of plenums fail their first air test?

70% of plenums fail their first air test as there is still a lack of understanding within the construction industry as to how airtight a plenum needs to be. Often people are working on information about plenums that have been tested in a lab under laboratory conditions, and as everyone that has worked on a construction site knows, there is a big gap between what happens in a lab to the reality of plenums on a construction site. With multiple contractors needing to put pipes, cables etc through the plenum, this is just one of many things that can affect the air tightness of a plenum. HRS have years of experience and can work with you to ensure you pass your air test first time.

Plenum Desktop Design Reviews and Site Advice Visits

HRS plenum desktop and on site design reviews assess how elements of the plenum are specified and how they are integrated together to form a workable plenum.

How is a Plenum Air Test Carried Out?

In brief, a tile is removed from the plenum for a celotex tunnel leading to the HRS fan.

Any air handling ducts serving the test zone need to be turned off, isolated and temporarily sealed, stopping the passage of air to outside of the test zone via ductwork. Once the area has been prepared and the fan set up, the test takes place in the same way as a HRS normal air pressure test, i.e. taking a number of pressure readings over a period of about 30 to 45 minutes.

If your air test fails, your HRS air tightness technician will carry out a smoke test to look for air leakage paths and sometimes it is possible to carry out remedial works.

What Standards are Plenums Tested to?

At present there is no set standard for plenum testing. The specification is usually set by the project’s Mechanical Engineers, and is normally set in litres per second per square metre (l/s/m2). HRS will need to know what pressure the specification is set at, e.g. 0.5l/s/m2 @ 50 Pascals. It is possible that the specification can be set in l/s/m3 and for this HRS would require the volume of the RAF Plenum.

Plenum Remedial Works

If your plenum has failed, don’t panic! HRS have extensive experience of carrying out plenum remedial works (when we have not be contacted at an early stage, to give the help and advise that is needed).

HRS’s practical and technical expertise means we can identify defects/problem areas and carry out the necessary remedial works.

If you are unsure of the Air Tightness services you require please call 0800 030 4391 or email and one of HRS Air Tightness Consultants would be happy to guide you through the process.

0800 030 4391

Knowledge Hub
“Just wanted to drop an email show appreciation for HRS operatives for the works that they carried out. They very knowledgeable and were able to guide and work with our site team,  in order to achieve satisfactory air tests.”
Project Manager, Kier Construction
“Please pass on my thanks to the air tester for there positive approach and his hands on attitude. Can you please also pass this on to his line manager in his professional attitude. I look forward to being able to use HRS again in the future.”
Quantity Surveyor, Morgan Sindall
“I would like to thank your air tester for his patience during the past tests. He has given me excellent advise which we help on future projects.”
Design Co-ordinator, Balfour Beatty Construction

Case Studies & Gallery

Please hover over an image and click the ‘Link’ icon to view Case Study information, or Click the ‘Magnifying Glass’ icon to see a larger photo.

HRS can provide you with a complete range of building environmental and sustainability services, meaning you can save time and money, avoid inconvenience and your risks are minimised.

From concept design stage to completion, HRS can work alongside you every step of the way. You and your project would be supported by HRS’s extensive knowledge that has been built up over 30 years, whether you need consultancy or on site advice and guidance, HRS’s large team of consultants and on site technicians are here to support you to make sure that your project hands over on time and within budget.

At HRS we believe strongly in being pro-active and customer focused, providing you with innovative cost-effective solutions.

All you need to do is make one phone call to 0800 030 4391 or email: sending one set of drawings stating what services you require, and HRS will take it from there.

Building and Enviromental Services from HRS

Relevant Accreditations

To see the wide range of accreditations that HRS Services hold, please visit our Accreditations page »

Need advice or a quotation give HRS a call on:
0800 030 4391 or email: