I know people can use too much, but have you ever been in a house where the owner had in every room a Glade plug-in? Talk about scent that was so strong it could have covered up something dead ... OMG.
We bought a house from a couple in their early 90s a few years ago for my SIL to live in. They had those in every room & took those with them when they moved. The problem was the odor had permeated the painted walls & it was as if the plug-ins were still there. We aired out the house leaving all the windows/doors open, but nothing helped.
We still had to paint all of those walls to get rid of existing wall colors (charcoal gray, chocolate brown & deep maroon). After painting with two coats of primer & two coats of paint, the odor was sealed in the drywall & it smelled so much better.
Needless to say, my SIL is one of those people who used scent beads in her laundry, perfumed soaps, burned Patchouli incense & all kinds of scented candles. My husband told her none of that was allowed in the new house ... no if, and or buts, period! We got the odor out of there & she wasn't going to replace it with something else.