Like i said it has to do with the script movement you are using for the player and the collision detection system you define, and nothing to do with the model itself.

The chair and the desk are made in a modelling program you choose and then exported to 3dgs. Its the 3dgs engine that handles the collision detection of that models depending on modes / flags you define.

So, what movement script are you using for the player movement and what 3dgs version are you using?