Re: Propane leak into the bilge. What to do?
The propane sniffers are designed to alarm at a fraction of the explosive concentration, so hopefully you were on board to hear the alarm and responded by turning the gas off at the bottle.
If you weren't on board, the propane has no business being on at the bottle.
Although propane is heavier than air, I would have thought there would still be diffusion going on so it will eventually dissipate from the bilge, given ventilation but not forced ventilation.
Which is a long winded way of saying : open all the windows and hatches, and access hatches into the bilge. Go away from the boat and wait an hour. Let the breeze do it's work.
I would have thought this is safer than operating any electrical switches for fans. What if the propane has filled the cabin too and the spark from the switch sets it off?
The advice for home gas leaks is open some windows and do not touch any switches. Get away.