Quote Originally Posted by pepi
I have two cars both have fuel cells with vented caps, carb induction, never have any fume smells, in the car or the garage.
My experience is much the same as Pepi's. I have a rollover vent valve, mounted in a pipe nipple above the top of tank about 4" with the vent hose routed high, coiled and then turning down to a bulkhead fitting on the trunk floor. I chased fuel fumes for months, but found that it was from running rich, leaving raw fuel in the induction runners, exiting the short lake style headers; and also once from a ruptured fuel regulator diaphragm dumping masses of raw gas into the tunnel ram. Once those issues were addressed my garage is virtually fume free.
The only time you'll see fumes emitted from the tank vent is in a significant increase in temperature of the tank volume. If the ambient temps are decreasing or running relatively constant there's no emission (in-flow if cooling), and in a normal temperature increase the fume volume emitted is quite low, likely not even enough to smell, IMO. As Pepi suggested, I'd say if you're smelling raw gas you have a leak liquid.