I do worry about Lithium batteries in general, I've the cycle pack in the garage, my cordless drill in the workshop and a powerfull Chinese torch in the hall.
If any of them decide to self-destruct my house will be a massive bonfire.
I think many households could say roughly the same, but as long as you are around when charging, and you make sure that any that get deformed for some mechanical reason are disposed of safely, you should be OK.
Lithium is simply dangerous, and if it starts burning, about the only way to put it out is to sink it in water for hours.....
All of the drills where I have opened up the battery over the years, its always been NICADs, but I am sure that you know what you have...
Learn what causes Li-ion to fail and what to do in case of fire. Battery makers are obligated to meet safety requirements, but less reputable firms may cheat.
batteryuniversity.com
If a Class D extinguisher is not available, douse a lithium-metal fire with water to prevent the fire from spreading. For best results dowsing a Li-ion fire, use a foam extinguisher, CO2, ABC dry chemical, powdered graphite, copper powder or soda (sodium carbonate) as you would extinguish other combustible fires.
We should all take great care with any high power battery.
In Germany, electric car fires often have to have a big tank of water brought close, and the whole car gets dunked in the water for an hour or so, to get the heat out of the metal....
Apparently the same happens in Holland too with electric car fires:-
For me personally, its a good reason to not have your family in one!
But each must choose for him or her self....
Andy