HEPA
| Date | Clue |
|---|---|
| 2026-05-31 | Purifying filter acronym |
| 2026-04-25 | Big acronym in purifying filters |
| 2025-09-26 | Purifying filter acronym |
| 2025-08-02 | Big acronym in purifying filters |
| 2025-01-31 | Big acronym in purifying filters |
| 2024-05-21 | Purifying filter acronym |
| 2024-05-03 | Filter acronym |
| 2023-12-31 | Big acronym in purifying filters |