CFD models aren’t always needed for smoke shaft systems

CFD models aren’t always needed for smoke shaft systems

‘Smoke shaft’ is the common term for ventilation systems in the lobbies of tall buildings, used to maintain tenable conditions in the common escape routes in the event of a fire in the building. Smoke shafts originated from research carried out by BRE and presented in a report in 2002 entitled ‘Smoke Shafts Protecting Fire Fighting Shafts, Their Performance and Design’.

This report specifically looked at firefighting shafts and proposed natural ventilation – with the output being commonly known as the ‘BRE Shaft’. The desire to reduce the space occupied by the ventilation system led to the development and common acceptance of mechanically ventilated shafts to provide both firefighting and means of escape protection.

Systems such as these are now the most commonly employed smoke control measure for high-rise buildings, overtaking the other available approaches, namely automatic opening vents and pressurisation.

Unlike the other methods mentioned previously, mechanical smoke shafts do not yet appear in the Building Regulations and are treated as a fire safety engineered approach. This means that although they are now very common, as they are a fire engineered solution, they generally require approval by the building control department on a case-by-case basis. As there is no single common standard applying to these products, they are typically approached using the appropriate parts of several related documents.

In addition, the Smoke Control Association document ‘Guidance on Smoke Control to Common Escape Routes in Apartment Buildings’ (Revision 2, October 2015) offers a comprehensive guide to smoke shaft applications for residential buildings.

CFD commonly used

Computational Fluid Dynamics (CFD) are commonly used to ascertain the volume flow rate required to maintain the design conditions within the lobby; this was essential in the early days of adoption of such systems as each situation was in effect a new scenario.

However, after more than ten years of common usage, there is a bank of data available to inform such selection for most buildings, particularly residential where one lobby is very similar to another. Fläkt Woods (now Fläkt Group UK) carried out research using data from dozens of models and found that for typical buildings up to 20 storeys the results were very similar and used this data to come up with a standardised approach to mechanical smoke shaft systems. The resulting product, the ‘Smoke Shaft Vent System’ was vetted and approved by Local Authority Building Control in March 2016 and is approved for use in all suitable buildings in England and Wales.

As approved installers of Fläkt Group UK’s Smoke Shaft Vent, SCS Group endorses this system which offers many benefits for specifiers, contractors, developers and tenants of high rise residential buildings. The use of the LABC approved system takes away the risk of gaining approval for the proposed installation and eliminates the need to model every building reducing time and cost. Other benefits include:

  • Instant availability of design information including technical submissions and operating and installation instructions.
  • An online selection and pricing tool.
  • Off-site assembly of extract plant and control systems allowing faster delivery and installation.
  • Remote monitoring and testing of system available as standard.
  • Ease of integration with other building services by direct communication via Modbus.

The system has been in use for four years and is already protecting many buildings across the UK.

Get in touch

For more information on the Fläkt Group UK Smoke Shaft Vent System and using it for your project, please contact either Mike Jackson or Matthew Thompson from our Pre-Construction Team or you can call them on 0870 240 6460. You can find out more about it at

Published May 2018