DRIFT (Dispersion of Releases Involving Flammables or Toxics) is an advanced gas dispersion model that has been developed in association with the UK Health and Safety Executive (HSE). DRIFT 3 incorporates a considerable number of modelling enhancements over previous versions of DRIFT. As well as modelling heavy gas dispersion, DRIFT now also models:

  • Buoyant lift-off and rise, following the recommendations in HSE Research Report RR629
  • Momentum jets
  • Finite-duration and time-varying releases
  • Thermodynamics of multi-component mixtures

DRIFT 3 also provides an Interface to the pool vaporisation model GASP.


DRIFT 3 is a completely new computer implementation coded in C++, with a new graphical user interface and a Component Object Model (COM) interface to allow the model to be run from Excel spreadsheets. The model has undergone extensive verification and validation testing. Recently published papers include:

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