I don't even run a bilge blower. It's probably one reason why I didn't blow up our Sun Runner when the main fuel inlet hose was leaking. And there was the first time I fueled up the SkipperLiner, and came back 2 weeks later, and smelled gas. Some boaters would've turned the blower on to get rid of the fumes. There was over 40 gallons of gas in the blige, and if I'd turned on the blower it's quite likely we'd been blown to kingdom-come. Me, I sniff, as BB noted above, raw gas is very easy to smell. Just my opinion but a bilge blower is oxymoronic- If I don't smell gas, I don't need it. If I DO smell, gas, the LAST thing I'd do is switch it on. And I don't buy into the 'ignition protected' BS. Bilge pumps are supposed to be, and look what happened to Lewis. Any whatsoever compromised wire connection is all it takes.
If I smell gas after fueling- like with the Sun Runner (which has been the only time in my boating life), I'll open the hatch and wait until it's aired out to suit me.