A quick mild rant: an ampere is a rate of electrical current flow. "2 amps per hour" or "2 amps per day" are pretty much meaningless terms (or rather, would be indicating some sort of change in current flow over time, somewhat like acceleration is a change in speed over time). Charging at 2A is charging at 2A, regardless of whether it's carried out for an hour or a day; in the first case, it results in a charge of 2 Amp-hours, and in the second, of 48 Amp-hours.
I would generally rather not have a flooded lead acid battery in the same room as me when it's being used, but that's more because of the tiny amount of acid that tends to escape over time rather than hydrogen gas generation. The amount of hydrogen produced at a slow rate of charge is very small, and hydrogen dissipates very rapidly in the open air--particularly if there's any sort of ceiling ventilation. If there's a chance of something failing and the battery being shorted out or charged very rapidly, then it's quite a different story; I definitely don't want to be in the same room as a battery that explodes or self-destructs!