Car park ventilation design using CFD

  • BS 7346-7 / NEN6098 / NBN S 21-208-2 / QCDD
  • Approved Document F, B
  • SCA guidance Ventilation design
  • Underground / Basement car parks
  • Jet fans / impulse fans / induction fans
  • Smoke clearance
  • Smoke control
  • Above ground / Multi-storey car parks
  • Natural ventilation
  • Mechanical ventilation

Ventilation is an essential design consideration when building a car park, whether the car park is located above or underground. As per the need, it keeps pollution levels acceptable, clears smoke once a fire is extinguished, assists firefighters, enhances escape or assitsts to omit provisions such as lobby vents and/or a stair split at ground level. We verify car park ventilation system designs using CFD simulations, or make a complete design meeting all applicable regulations.

Would you like to discuss your car park design


Building codes set out guidelines how to design car parks, whether they are located above or below ground level. Depending on the availability of ventilation openings car parks are required to be ventilated for daily operation (pollutants) and fire alarms. The recommended air circulation can be accomplished via natural, mechanical or assisted natural ventilation. When sufficient openings are available the main air flow can be generated by utilizing impulse fans only, saving space and costs of extract and/or supply shafts. Required ventilation rates are commonly set between 3 to 10 air change per hour (ACH), depending on available ventilation openings.

The overall ventilation requirement is calculated in terms of overall ACH of the system. More detailed methods to verify the ventilation efficiency locally throughout the car park are also in practice, such as the age of air (AoA), which is recently adopted in the latest guidance document from the Smoke Control Association (SCA-UK). This technique allows highlighting the recirculating and/or poorly ventilated zones and assesses the local ventilation efficiency at every location in the car park.

British Building Code Approved Document B and Approved Document F refer to BS 7346 for varying design objectives. For instance, the car park smoke studies can be performed to demonstrate compliance with a Clause 9 smoke clearance system or a Clause 10 for assisting fire-fighting access. Besides the UK we also have a broad experience with car park ventilation designs for Ireland, Germany, Netherlands, Belgium and the UAE.

Purpose of CFD

Smoke ventilation systems in car parks aim to replace the contaminated air in a car park by fresh air. This is achieved by means of exhaust and supply ventilation provisions often aided by thrust fans. When designing such a system the aim is to make an efficient design without utilizing excessive resources.

While accomplishing that, short circuits and stagnant points are desired to be avoided. However, that goal gets challenging in complex geometries with elaborated ventilation system designs, composed of multiple extract or supply points, thrust fans and ventilation openings possibly influenced by wind. This is an area where computational fluid dynamics tools (CFD) can be extremely helpful. Even more when additional objectives are included, such as providing fire-fighters access or keeping lobbies clear of smoke.

Complete assistance

One Simulations supports you with verifying your car park ventilation system design using CFD simulations as an independent company.

When needed we can even design the entire system by strategically placing equipment to comply with all local requirements and any additional objectives.

We provide support during (concept) design and assist with discussions with local authorities such as building control or 3rd party reviews. One Simulations is the solution expert you can consult for any car park ventilation system.

CFD simulations are used to:


  • Ventilation systems for daily operation
  • Ventilation systems provinding smoke clearance or fire-fighting access
  • The absence of stagnant areas
  • Equivalent performance for alternative designs


  • Clear demonstration of the performance of the ventilation system
  • Compliance as per applicable regulations
  • Allowance for the use of hybrid systems consisting only of thrust fans, saving on shafts
  • Approval from (local) authorities

What do we offer

We have an in-depth knowledge of Fire Safety Engineering and a long history in the application of CFD in this field. A significant increase is seen in performance-based building designs being put into practice. Developments in engineering tools and the higher performance of calculation computers allow for going beyond the back-of-the-envelope methods and allow designers to push the boundaries of their building design. One Simulations makes use of industry-leading calculation software and performs calculations on an in-house dedicated high-performance computing (HPC) cluster. This allows us to increase accuracy, with significantly reduced simulation run times and thus shorter turnover times.

Aside from executing the calculations, our team also regularly performs third-party reviews for CFD projects. We can review CFD simulations executed in any software, such as Ansys CFX, Fluent, Fire Dynamics Simulator (FDS), OpenFOAM, etc. See also second opinion services.

While our work cost-effectively gives freedom to designs, the results are reported with a focus on code compliance and legislative requirements.

Feel free to contact us at an early stage so that we can share our knowledge and experience with you.

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