| GASES | Hydrogen and methane, etc |
| GASSES | Hydrogen and methane (Var.) |
| NEPTUNE | Planet whose blue colour derives from its gaseous atmosphere of helium, hydrogen and methane (7) |
| GREENHOUSEGASES | CO2 and methane, to a ecoscientist |
| GREENHOUSE | Gases such as carbon dioxide and methane (10) |
| WATER | Substance composed of the chemical elements hydrogen and oxygen and existing in gaseous, liquid, and solid states. (5) |
| HUMIDITIES | Hydrogen and blend of 28 and iron? It makes air damp (10) |
| HUMIDIFIER | Hydrogen and blend of iridium and iron? It makes air damp (10) |
| STAR | Any one of a series of astronomical fusions of mainly hydrogen and helium forming constellations and asterisms (4) |
| TRITIUM | Radioactive isotope of hydrogen, occurring in trace amounts in natural hydrogen and produced in a nuclear reactor |
| GASGIANT | One of the four planets in our solar system that are composed chiefly of hydrogen and helium, namely Jupiter, Saturn, Uranus and Neptune (3,5) |
| DEUTERIUM | A stable isotope of hydrogen occurring in natural hydrogen and in heavy water |
| WATERGAS | Fuel consisting of hydrogen and carbon monoxide |
| AMMONIA | Compound of hydrogen and nitrogen (7) |
| AZOTH | What's mostly nitrogen, hydrogen and mercury |
| HOHUM | Hydrogen and oxygen smell uninteresting (2-3) |
| NACHO | Snack of sodium, carbon, hydrogen and oxygen (5) |
| SULPHUR | Picked up ruthenium, hydrogen, and also ________? |
| GASEOUS | Like hydrogen and chlorine |
| HAG | Old woman fuses hydrogen and silver (3) |
