Did You Know if you have several volumes in your model, and some of them represent solid and others represent fluid domains, you only want a boundary layer to be grown for the fluid domains. The solid domain should be meshed with tetras only (no boundary layer). In the CFD tetra mesh panel you can select the fluid domains via the selector shown below.
Example: Some electronic components (green cylinder, purple box, solid domain) are placed in a bigger box (fluid domain)
Only in the fluid domain a boundary layer was generated, the cylinders and the purple box were filled with a pure tetra mesh.