I used my gen only for many sporting events trips. No, gen fumes are not enough to set off the detector but there is a slight smell. You don't realize just how much until you get the genturi and realize it eliminates any smell. When its windy the exhaust goes right under your MH and seeps in that way too.
My gen exhausts along side a large window which is where the couch is. Which is where I end up sleeping 99% of the time.
For months I thought my headaches in the morning where just from all the activity from the prevous day. Once I started using the Genturi the headaches went away. I believe because it eliminated the slight amount of fumes from coming in.
I just wish ALL sporting events and ALL CG's without power would REQUIRE exhaust stacks. Just spend 5 days at an event with hundreds of MH gens running, whew, everything smells like exhaust!
BTW: just beware that homemade ones get VERY hot and can melt the side of your coach and/or burn anyone passing between RV's. I've seen numerous pics posted of melted RV sideways from a DIY exhaust pipe.
Genturi specially made pipes are NOT hot to the touch. You can run that gen all week long and when you are ready to leave you can wrap your hand around those pipes to take them down.