I finally got around to wiring up my fuel vapor detector and CO monitor..

Now I'm having problems with false alarms from the fuel vapor detector.

Have had a Zintex fuel vapor detector in the engine compartment
operating almost continuously for over ten years now. The sensor has
a limited life span (and limited shelf life) and fails safe; mine
started falsing at six years and required replacement. Essentially
they become more sensitive as they degrade and signal unnecessarily
when vapors are below 20% LEL. The factory said they last longer when
continuously powered up; expect 3-5 years when used intermittently.
Although yours is new; maybe that's the problem, an old or defective
sensor.

I find it hard to believe the problem is hydrocarbon leakage from the
engine if there's no falsing while the engine is running.

Splash water or immersion quickly poisons the sensor; has yours gotten
wet in the past? I faintly recall shortening the sensor cable is a
no-no; that might cause falsing. Prior to coughing up $60 for a new
one can you test your sensor by borrowing a dockmate's and seeing if
the problem persists?

Also, be aware the detector is very sensitive to hydrogen, so wet-cell
battery gassing will trigger it if there's a route from the batteries
to the engine compartment. A 13.8v float voltage triggers mine after a
few hours on a calm day, 13.4v doesn't.

If you're running a 3 stage regulator and the batteries are fully
charged before engine startup, the regulator will quickly reach the
14.4v acceptance phase and vigorous gassing will start. Takes a while
for the concentration to build up at sensor height because hydrogen is
lighter than air. If your blower is on while the engine is running,
it might adequately vent the hydrogen until you shutdown the engine.
I asked the factory about this and they said hydrogen is much
"stickier" than big molecule hydrocarbons and it takes a while for the
sensor to flush itself if a high hydrogen concentration triggered it.

Of course, if you have gelcells or AGMs that's not the problem g.