Safety procedure when working around sour gas wells (natural gas with H2S) is that, if you see somebody drop in front of you, you do not touch him, approach him, or anything else. You just get the hell outta there. If he's been dropped by H2S, trying to move him is just going to cause you to go down too. Besides being bloody lethal, H2S is notorious for being corrosive. H2S forms metal sulfides with any exposed metal it can access, and the hydrogen byproduct often diffuses through the metal and forms expanding holidays in positions of stress, potentially to the point that the metal will crack.

I've worked around high power free-space infrared lasers where a single stray reflection could instantly blind you permanently (and you can't see infrared light scattering off of stuff like you can with visible lasers). I'd rather spend years working with those than spend one afternoon in a lab with a sample of H2S at 140 GPa. I don't care if it's inside a diamond anvil cell inside a cryostat. High pressure H2S has got to be a freakin' nightmare to work with. I'm sure H2S has lots of funky properties nobody knows about because practically nobody wants to work with the stuff. Kudos to the PI who convinced a bunch of grad student peons to put their lives on the line... I suppose.

> in a lab with a sample of H2S at 140 GPa. High pressure H2S has got to be a freakin' nightmare to work with.

They probably have absolutely tiny quantities of the stuff under pressure. Not enough to hurt anyone even if it escaped.

Reading the arxiv preprint, they fed H2S into a DAC using a capillary. The size of the sample under pressure was 1um thick and 10 um in diameter, which is indeed tiny. So, that's probably not so bad. Anyone who thinks this would make a great room temperature superconductor in real applications had better smarten up though.

"it becomes odorless (by paralyzing your sense of smell) right around when you need to start getting worried"

I don't know if this is still the case in this litigation-happy age (probably not), but when I was in high school it was a common beginner's chem class experiment to make small quantities of H2S.

My physics teacher once commented that he hated it when they did that, because he'd smell it for a while, then not smell it any more -- leaving him to wonder whether it'd just gone away, or whether people were going to start keeling over.

Ah the good old days of worry free high school chemistry/physics classes. My chem teacher poured out a pint of mercury and allowed us to push our fingers into it to feel how different it was from liquids like water. Good times.

Elemental mercury is not very dangerous:

https://en.m.wikipedia.org/wiki/Mercury_poisoning

The danger is that some will spill and lie there on the floor for months, filling the room with mercury vapor.