I must disagree. I never smell gas around any of my older cars, except when they had a noticeable leak, and that is parked in a home garage. A building garage is even more open, so unlikely there isn't a true leak.
I'd also first suspect the fill grommet, which cost ~$12 and takes ~2 hrs to change, if tank is almost empty and you take time to clean and paint rust. Wherever it is coming from, it should be visible.
