I disagree. If something happens with an apparatus, you fucking shut the hood quick. There is very fast positive pressure air blowing in through the sash opening, the apparatus is bolted into the wall, sashed above the nonglass barrier, and there is negative pressure inside the apparatus, so the tendency is to not leak out but leak in.

If you have a 5% aqueous solution most of that HF is still binary undissociated HF, which will leak into the atmosphere so you could very easily unawaredly be breathing it in if you are working with it in any open air situation below the sash line (which is what the tendency is when you're working with aqueous concoctions).