Computational fluid dynamics (CFD) has proven its value and its validity in simulating cleanrooms. However, the user's engineering judgment is still crucial to a successful CFD modeling job. When applying CFD software, caution must be taken to include all the relevant physics in the model. For example, in a cleanroom application, diffusers and major flow obstacles must be represented. In addition, heat sources such as heat generated by human occupants and equipment must also be included to produce an accurate solution. To ensure accurate results, general guidelines for simulating cleanroom design, some of which are listed below, should be followed.