The odor simulation is implemented as a physics plugin for Webots, and therefore lies inside plugins/physics/odor_physics. This folder contains a multitude of files which implement a piece of the model each. The file which holds the whole simulation together is odor_physics.cpp, more precisely inside the function "webots_physics_init". All model parameters can be easily be configured there.
The parameter names should be mostly self-explanatory. In addition, there is short documentation in the file implementing that corresponding part of the model. (At some point in the future, a better documentation of these components will appear in this book.)
After changing the model configuration, the plugin needs to be recompiled by typing make in the folder of the plugin, and the Webots world needs to be reloaded.