I have been using li-poly cells for 10 yrs or so, they are stored in a vented steel box because they can spontaneously cumbust for no apparent reason, but they are particularly dangerous when charging or when damaged, cell damage is not always external or visible.
A li- poly fire gives off a very caustic smoke that will destroy every metal, electrical and electronic circuit inside of the garage.
People should be aware of the inherent dangers involved.