to add to the words of others ... i've never heard that wet-cell batteries are a problem in a boat cabin.  i've slept in many a boat having wet-cells ... including my M15.   having just completed adding an electrical system to SCRED (my M15); this mentioned danger may be when the battery is being charged.  don casey in SAILBOAT ELECTRONICS SIMPLIFIED does mention having awareness that when charged a wet cell will release oxygen and hydrogen AND never work on a electrical system when it is being charged as a spark by cause an explosion.  he also states the battery compartment needs 'effective ventilation'.   a gel cell can gas if overcharged.   the oxy and hydrogen released from batteries are highly corrosive to electrical components.   you will have no gas (besides the human crew) if that batt(s) is not charged on-board.   a gell cell has 1/4 less life (total cycles) than a same sized wet cell.  a gell will take (and release) a higher change more quickly making them good for high loads that run for a short time.   the most cost effective battery remains the wet cell.     dave scobie M15 #288 - SCRED visit Scred's www-site: http://www.freewebs.com/m15-named-scred --- On Fri, 4/24/09, Richard Everett <rick@skyko.com> wrote: Hi guys, I was showing our M17 to a fellow interested in purchasing a new one and he was alarmed that the two batteries (I added a 2nd battery and a 1/2/all selector switch to be prepared for the group San Juan trip) were not gel cell type, but rather the traditional marine deep cycle trolling motor type wet cell.  He said it was a big no to use that type of battery in an area where you sleep. What do you guys think?  With ventilation, is the outgassing from these batteries a possible danger for us? Thanks Rick M17-635 Eidolon