| Clue | Source | Date |
|---|---|---|
| Mixture of carbon monoxide and hydrogen | New York Times | 25 May 2025 |
| Fuel was spread over grate, haphazardly | The Guardian Cryptic | 10 Jun 2022 |
| Fuel was great for cooking | The Telegraph Toughie | 20 Jun 2018 |
| Fuel consisting of hydrogen and carbon monoxide | USA Today | 05 Nov 2016 |