That will handle the heat from a fire but you want to have ventilation in that area. The smoke and fumes from a battery fire are very toxic.

Lithium reacts with the air once exposed and that is why there are flames. If the box or device allows the chemical reaction to vent out but not allow fresh air in then the event is less aggressive. The box I made has vents and baffles to block flames from jetting out. I destroyed about 12 battery packs in one test with out any damage to surrounding flammable materials.

Another consideration is the fact that any LiPo pack expands as it fails so you have to account for the increase in area it takes up. Otherwise the container could become part of the problem.