"Commercial" just implies commerce; that it was a product that could be purchased. It was not a consumer product. In the article it says the title was "Industrial Laundry Rust Remover".

There are certainly much nastier chemicals used that this in industry. As an example, I'm reminded of a quote by Gordon Moore about Intel having melted their sewer pipe, in this article:

https://www.bloomberg.com/news/features/2017-06-15/american-...

I'm guessing it came from "another era" where you could buy stuff like this without an issue?

But even few years ago I visited a wolfram mine in Portugal on a job, and was told by the guy I worked with at the time that the miners are using stuff "banned long time ago in UK" to clean the tips of the guiding ropes which we were replacing. I was never told what it was, but nowadays I suspect it was HF.

For those who might be confused, "wolfram" refers to Tungsten.

Key word is "commercial". The commercial world is full of dangerous substances (when you leave the safety of an office and go into the dirty world of production :-)), out of necessity, but you are assumed to have received proper training and be in possession of proper safety equipment.

Concentration has a lot to do with it. More dilute solutions of HF may cause burns, but t it's unlikely to kill you.

Concentrated HF is another beast entirely.

And given that it was in an old dusty bottle packed away deep, it may have concentrated over time due to evaporation.

Acids tends to pull moisture from the air (hydroscopic) and dilute rather than lose water and concentrate.