Fuel Vapors and possible leaks

I need help figuring out why I constantly smell gas inside my car. I notice that when my tanks get to a certain level the vapors become stronger. I had the car checked for leaks but the mechanic could find no leaks. He replaced a hose and thought that this would solve the problem but to no avail. Could this mean I may have a leaks, problem with the tanks What?:uhoh: