Hydroflouric acid from burning Lithium batteries? I would like to see your chemistry. Hydroflouric acid production is already a problem with ICE engine compartment fires. It is due to PTFE insulation on wires getting hot enough to denature. Fire services are aware of this, and take precautions to avoid exposure.
Hydroflouric acid is indeed very nasty stuff. Unlike, say, sulphuric acid, it does usually not burn on contact. But over a few hours, it penetrates the skin, and the flouride ions then muck up calcium chemistry in the body, by making calcium into insoluble flouride.