When I was in university, I lived in a residence and there were two girls down the hall that smoked constantly and had a bunch of air fresheners going, with the overall effect being a disgustingly cloying mix of tobacco and synthetic berries or whatever. I've experienced the same thing with those bathroom fresheners where people think spraying them will cover up the smell they produced, and you end up with this revolting mix of poo and air freshener.

Overall, I'd almost always rather smell the actual thing being covered than the smell of it being mixed with air freshener, and I assume, bacteria contamination aside, it's a lot healthier not to breath in whatever the fresheners are giving off