cell batteries are made for indoor use. no so in car batteries. not even close to the same. inverters are used in campers and RV's, alot. notice where the batteries are? in ventillated closets. car batteries contain acid, which does evaporate. feel free to have them in a home. they surely won't be in my home. here's what the label on one i have sitting in my shed. i went out to read it to get the words right..."There is a risk of explosive gases being released when lead acid batteries are being charged or discharged. Failure to follow instructions may cause property damage, explosive hazard, and/or personal injury."