The scientist in me is quite pleased with today's theme. There are three common molecules, all typically encountered as gases, represented in their standard chemical notation in the grid. METHANE comes up as a C surrounded in each direction by an H, while the double bonds found in CARBONDIOXIDE shows up as OCO in AMOCO. It's quite clever, and the placement of the molecules makes them seem like they're actually floating in the grid.
It's a nice find that WITHCHEESE and JOHNHUGHES are the same length, both with those H_H patterns. I'm not as used to seeing AHCHOO as "achoo" in the grid, but DONHO is an old friend.
There are definitely some tradeoffs in the fill, however. The middle W section is rough, with ECONO prefix, MOLAR crossing MALAR and abbreviation MAJ. The middle E section is better, even with OMG crossing NGO. I made a silly error by misreading 26D: Easily changing emotions (MOODY) as describing the emotions rather than the person experiencing the emotions, and put in MOODs. Always check the crosses!
Also finding IMAC and IPOD in the same puzzle?
On the other hand, who doesn't like 4D: Group in a pit (ORCHESTRA)? And 24A: Wearers of kilts (SCOTSMEN) is also very good.
On the other other hand, I could do without the image conjured up by HOTWAX. Guess I'm just swimming in my male privilege.