| Clue | Source | Date |
|---|---|---|
| Hardest to see through, perhaps | Wall Street Journal | 25 Aug 2022 |
| Time after moment in heavens is foggiest | The Telegraph Toughie | 17 Jan 2018 |
| Most in need of a chimney sweep | ||
| Most fuliginous | ||
| Most poorly ventilated, as a pool hall | ||
| Haziest |