Is impurity transferred if one sits, walks, or touches impurity and no trace or smell of it appears on the body or clothes? And is it judged that it is not transferred if a trace or smell is found, but it is not confirmed to be impurity?

If one sits or walks on something impure and dry, and the impurity itself is dry, the impurity does not transfer. However, if either of them is wet or damp, the impurity may transfer according to many scholars. It is permissible to adopt the easier opinion to remove hardship, especially for those who suffer from obsessive doubts.