Note that he&#x27;s primarily taking about HF gas, not the aqueous solution.  Aqueous hydrofluoric acid is certainly not to be trifled with but I don&#x27;t think it&#x27;s in quite the same category as some of the other substances this guy talks about.  I used to work in a lab that used large quantities of the stuff and I knew someone who got some on his skin.  He went to the hospital but I don&#x27;t think he suffered any lasting consequences.