Smoke modelling is a technique for simulating the way smoke and heat will behave in the event of a fire.

In certain types of building, such as internal corridors in residential blocks using mechanical ventilation, shopping centres or  buildings with an atrium, smoke modelling is likely to be required as part of the standard design process and for approvals.

In others, it might be used as part of a fire engineering justification for a building ( an example could be to justify extended travel distances).

There are two main types of smoke modelling available, CFD smoke modelling and zone smoke modelling.

Computational Fluid Dynamics (CFD) Smoke Modelling is a very different approach. The basis of the technique is that the space that is to be modelled has a (3D model) built into a computer program, which breaks the space into a large number of individual cells (typically hundreds of thousands). The computer program then uses fundamental laws of physics and fluid flow to analyse the flow of the air and smoke between each cell for the duration of the fire.

CFD analyses take longer than zone models to set up within the computer simulation, and each analysis can take several days to run, even on high specification computers. However, they can analyse smoke flow in a much wider range of scenarios than are possible by using zone models. The also provide a 3D view of smoke travel, velocity and tenability for Fire Brigade access that’s easy to interoperate by enforcing authorities.

Zone smoke modelling is a technique that is based on equations derived from practical experiments. For the building that is being considered, as long as the physical geometry and possible fire scenarios are within the limitations of the fire tests that have been carried out, zone smoke models are a perfectly acceptable way to predict the likely smoke flow rates.

Zone models have the advantage that they are relatively simple and quick to carry out. However, if the building shape or fire scenarios are outside the limits of the experiments that were carried out, zone models cannot be used. However approving authorities’ may require more specific analysis to demonstrate performance. They are therefore only useful in certain specific situations.