Been there done that- In my personal mod I added chlorine, nitrogen, sulphur dioxide, helium and neon. I wasn't going for the realism that you are. But don't rule out the noble gases- they are used as exotic diving gases- Argon and Xenon are too narcotic, Krypton causes dizziness and Radon is radioactive. Neon though expensive is a good replacement for helium.
Trimix is also good as it is a mix of O2 He and N2.
Hydrogen sulfide is a good choice but causes smelly planets
If you're just looking for other possibilities;
Nitrous Oxide---A very happy planet
Ethylene---ancient Egyptians, who would gas figs in order to stimulate ripening.
Sulfur hexafluoride---SF6 is the most potent greenhouse gas, with a global warming potential of 22,200 times that of CO2.
Hydrogen chloride---Very corrosive forming HCl acid in the presence of water/humidity
Nitrogen Dioxide---This reddish-brown gas has a characteristic sharp, biting odor. NO2 is one of the most prominent air pollutants and a poison by inhalation.
Vinyl chloride monomer---Until 1974, VCM was used in aerosol spray propellant. Prior to the removal of VCM from hair spray the accumulation of vinyl chloride vapor in hair salons may have exceeded the NOAEL (NO Adverse Effect Level) exposure guidelines. Just an odd fact.
Deuterium Gas---Don't know much about this one
Phosgene---This gas gained infamy as a chemical weapon during World War I, but it is also a valuable industrial reagent and building block in organic synthesis. It is colourless, but can appear as a white or yellowish haze when released into air, Chlorine light.
Silane---chemical compound with chemical formula SiH4. It is the silicon analogue of methane. At room temperature, silane is a gas, and is pyrophoric — it undergoes spontaneous combustion in air, without the need for external ignition. Silicon based life forms?
Hydrogen cyanide (HCN)--- is a colorless gas with a faint bitter almond-like odor. Very poisonous.
Dimethyl sulfide--- In vapor form it is produced by cooking of certain vegetables, notably corn and cabbage, and seafoods. It is also an indication of bacterial infection in malt production and brewing,and a disagreeable odor. DMS is the most abundant biological sulfur compound emitted to the atmosphere. Emission occurs over the oceans by phytoplankton.
Re: Expanding Atmosphere Types
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