| Clue | Source | Date |
|---|---|---|
| What O can stand for | Newsday | 17 Apr 2026 |
| Carbon ---, lethal gas | The Times Specialist | 05 Jan 2026 |
| Carbon ___, dangerous gas | ||
| Carbon ---, dangerous gas | The Times Concise | 02 Dec 2024 |
| Car exhaust gas, carbon ... | ||
| Oxide containing just one atom of oxygen in the molecule (8) | ||
| Carbon ____ | The Guardian Quick | 21 Nov 2023 |
| See 8 Down | The Telegraph Toughie | 26 Mar 2021 |
| Carbon ..., a poisonous gas | ||
| Chemical process involving small number on team | ||
| Carbon --, deadly gas |