Ok, everyone. I’m going to harness the power of chemistry to explain why Dirk’s planet is the only one that needs gas masks.

Obviously, Jane walked around on her planet without needed special breathing equipment. As anyone who has ever seen a balloon should know, Helium is lighter than air. The gas appears to be exuded from vents in the earth. Some of it goes into the balloons, but the rest would rise above the heavier breathable air (which is mostly Nitrogen, interestingly enough). You might get a squeaky voice from LOCAH, but you won’t suffocate.

Neon is also lighter than air. All Noble Gasses are colorless until a current is run through them. The presence of colored bands in the atmosphere of LOPAN suggests that there are clouds of charged particles floating around in the upper layers. This could lead to some interesting weather patterns, included storms and lightning, so that’ll be fun to look out for.

Xenon is heavier than air. Jake’s planet, LOMAX, has a big X marks the spot canyon in the center. The heavy Xenon gas would sink into this rift. Since it’s glowing, it must also be electrified. I would avoid going down there, especially since Xenon is an anesthetic. You’d probably pass out before you were electrocuted or suffocated.

Krypton is also heavier than air. Unfortunately, Dirk’s planet doesn’t seem to have any wells for the gas to sink into. Therefore, breathable air would be forced higher, and if you walked on the surface you’d get a lungful of Krypton. Though Krypton is not toxic, you could suffocate if that was all you had to breathe. It also creates a feeling of euphoria similar to nitrogen narcosis… in other words, you’d be getting a little high. I’m guessing there are so many skyscrapers on LOTAK because the consorts, whenever they were alive, built higher in order to reach breathable air. 

In conclusion