Why do i smell gas when car is parked and there are no leaks?

It has a leak somewhere. Hard to explain, but Vapors can escape and evaporate without puddling. There are some defects which the onboard diagnostic system do not monitor.

You could have a leak in the fuel line, intake manifold, or pressure regulator. Sometimes a chemical dye is added and an ultraviolet light will reveal a leak. This is easier to understand if you view Alcohol which is a component of gasoline. Pour out a few drops of alcohol from a bottle and you will see that it evaporates. This produces a smell and no residue to attribute the location of the leak. A chemical dye can leave a deposit that you can trace.

There is a leak somewhere or you would not smell gas. make sure your gas cap is sealing when you screw it on.