There have been comments on the forums about gases not diffusing properly. In order to test this, I used the debug tools to create multiple types of gas and let them combine. The gases in the picture are, from top to bottom, Hydrogen, Helium, Oxygen, Chlorine, and CO2. These are the problems that I notice:
- Diffusion is far too slow. Even after nearly a full cycle of waiting for the gases to reach equilibrium, there's still a factor of 1.5 difference in pressure between the left and right sides of this room, increasing to a factor of 3.5 in the CO2 layer.
- Pressures do not equalize between gases. All gases are still at approximately the same density they were created at (1kg/tile, within a factor of 2). At equal pressure, the Chlorine should be 35 times as dense as the Hydrogen.
- Densities are incorrect. Using the game's assumption that gases will stratify rather than mix, the densest gases should be at the bottom. Chlorine gas (mass ~71) should therefore be below CO2. (mass ~44).
- Low-pressure boundaries. Most tiles that form a boundary with another gas have a much lower pressure than the rest of that layer, by a factor of 5 or more.
Create one large room with multiple types of gas. Observe them while they stratify.