Dunae,
I've been under the impression that the more conventional liquid-based automotive or marine batteries were more prone to discharging noxious fumes - vaporized acid and hydrogen being of chief concern. In discussions of using them for solar power they warn to make sure that the batteries are both enclosed and safely ventilated.
The term Gas Recombinant cells certainly implies that they wouldn't pose as much of a problem. What about the "gell cells" that are originally supplied with stock UPSs?
If the stock cells are as bad as conventional "wet" cells, then wet cells wouldn't be any worse and all you'd need to worry about is keeping the "box" upright. ----------------------------------- Further notes on battery types:
Motorcycle batteries are subject to more radical changes in orientation, and usually vent through a tube that can be routed away from things that acid might harm.
Miatas and some other cares now use a battery that has a sponge-like fiberglass fill that gives some of the advantages of a gell cell while not having the problem of the gell shrinking away from the plates.
In aviation, it's more common to see "wet" Nickel-Cadmium batteries as well as conventional lead-acid batteries. NiCads deliver higher current for a longer time than equivalent weight lead-acids. (There has been a lot of advance in conventional battery design, but aviation tends to stick with old tech because it's tried and true.)
There's a lot of information on the web and in the public library on alternative power systems, particularly oriented toward solar and wind, that use batteries for storage and load leveling. I'm sure some research would pay off. --------------------------- Duane, you could take some of the posts you've made over the last few years and make a "UPS Upgrade HOWTO" - as I recall you have somthing like that already on your web site.