I wonder if part of the answer is different habits with respect to perfumes, soaps, and also in how homes are furnished, decorated, maintained and what products

I wonder if part of the answer is different habits with respect to perfumes, soaps, and also in how homes are furnished, decorated, maintained and what products are used (cleaning, detergent). And smoking, too. I could tell a friend had just left their home from the odor when they lived at a particular place¹, and sometimes, I can tell if some item of clothing has been left at some place (not that I'm special at that). The odor the author of the article could smell at her place after renting it for a month could have been a (mix of) perfume(s) their guests used. Obviously, people have their own odor on top of (or under, more accurately?) that. ¹ in a forest ­-- no, I'm joking.