Ron:
There really has been a huge discussion on this. I have been using my tank ocassionally in the winter inside my pole barn. I used it in my cabinet shop during the winter as well. Mind you I have a pretty good extraction system in my cabinet shop - it can change all the air in the shop in a couple minutes. In the pole barn I plan on using a fan - either an old range hood or a 6" duct fan to handle the extraction in the pole barn.
midmo wrote:Can the gases get to the point of exploding?
I sincerely doubt it. If you are using a small say 30 amp charger there will probably never be enough hydrogen generated to cause an explosion simply because there is probably at least 9,000 cubic feet of air in your barn that would need to be diluted with enough hydrogen to get to that point.
One way to ensure that start up sparks from a motor doesn't cause a problem is to ensure that the motor is either enclosed or is a sealed unit.
As an aside, when I was a little younger and still had a nasty habit (smoking) I used to partake of said nasty habit whilst e-tanking and never had a problem That either means that I was just dumb and lucky or that there was never a significant amount of hydrogen off-gassed to cause a problem. Course this is JIMHO and is not based on empirical data, just anecdotal.