Right, the EtOH/azeotrope is the normal domestic (industrial grade) product available where I am (Australia), it's available in all supermarkets, etc. That said, it often has impurities that ought not be present (see my other post).

Here, 'absolute ethanol' is typically 99%. No doubt H2O is a significant part of that last 1% but going on my experience with 95% EtOH I wouldn't be a bit surprised about it being benzene and it's likely there's other undesirable stuff as well.

BTW, over the years I've bought a lot of industrial grade 'absolute ethanol' which I use in woodworking as a solvent for shellac. 95% EtOH is unsatisfactory as the water in it often causes the shellac to turn a cloudy/milky colour.

I have to buy the 99% grade in 20-litre plastic containers as usually that's the smallest amount that's supplied. Moreover, it's much more expensive, at least double the price and on par with that of isopropanol.

Given its price and comparative rarity I doubt whether its consumption would be a signifiant problem. Anecdotally, the stuff I buy seems to have significantly more denatonium than the normal EtOH, quite some time after using it I've momentarily held my (dry) hand on my face near my mouth and the denatonium is almost overpowering. That's not the case with normal domestic EtOH (in the same situation denatonium is present but nowhere near as objectionable).

Absolute ethanol in the US is a chemical product and does not have denatonium in it. It isn’t much used, but you will sometimes see it in chemistry labs for IR spectroscopy. It’s at least 99%, the whole point of it is having a solvent that wipes out that huge water absorption band on IR so you can see the rest.

You'll note I've put absolute alcohol in quotes, here I'm referring to industrial/commercial grade 99% EtOH that's required in processes that cannot tolerate the 5% H2O such as in the application to which I've referred.

Clearly this grade should have denatonium added no matter where it's sold and I'm surprised that it's not readily available in the US. Moreover, there's no technical/chemical reason why denatonium shouldn't be added given that so little is need to be an effective bitterant. It seems to me the residual 1% 'impurities' would be much more relevant than the denatonium, even then, for most purposes, this 1% is already insignificant as far as the EtOH chemistry is concerned.

On the other hand as you note absolute ethanol as used as a reagent in precision experimentation (and in the pharmaceutical industry) would have to be devoid of denatonium. I'd add these grades usually come with a certified purity analysis/impurities percentage list together with the complying standard, BP grade, etc.

I'm unfamiliar with the regulations covering denaturants in the various countries but it seems to me the normal 99% grade with denatonium of the type I use is suitable for most purposes including most undergraduate lab chemistry (there's little point unnecessarily tempting students to imbibe).

Incidentally, when I was studying chemistry the denatonium option wasn't yet available so labs always had absolute EtOH available and the normal commercial denatured grade was roughly EtOH ~80%, MeO ~15%, pyridine ~5%.

I'm now curious as to how US-based woodworkers and painters manage using shellac if 99% denatured EtOH isn't readily available.