On my last boat a Sig 290 that was the out vent on the starboard side. So I could smell the air coming out. If your blower is on the starboard side, that should out an out vent. If not, I would just turn the blower around. Better still, move it to the other side so its sucking air from a low point and out.
Anything in the engine compartment must be ignition protected. If a fuel line was to let go and that side was the out vent you would know it in a second.
When I had my 2011 Sig 290 it was new. Every other trip, except long ones, I would go in the engine compartment and look around for anything out of place. Smells, leaks, wiring, stains just anything. I never took the dog or the wife off the boat when refueling. But the blowers were on so if gas was leaking I would know in a heartbeat. Your nose would tell you before a fume detector.
I installed an auto fire extinguisher, a FireBoy fixed system. If your worried about a fire when refueling. What would happen if you had a fire underway? To me that was more concerning with 2 engines running, the boat bouncing and I would never smell it. Yes the fume detector, helpful, but it can't put a fire out. Good luck with all this.
To back up a bit, if some boats do have the fuel and the air intake on the same side. Which I think is wrong, but who am I? Then I can see the fuel docks as a rule wants the blowers off until the cap is on.