| Chitchats |
| Fuels (up) |
| Space fillers? |
| Neon and argon |
| Neon and others |
| Helium and neon |
| Shoots the breeze |
| Hydrogen and methane |
| Some are combustible |
| Great times, slangily |
| Helium and neon, e.g. |
| Helium and neon, for two |
| Hydrogen and methane (Var.) |
| Dangerous buildup in a mine |
| Neon and argon, for two (Var.) |
| Radon and carbon dioxide, e.g. (Var.) |