Summary of sampled PM₂.₅ concentrations combined and individually for four prisons pre- and post- smoke-free implementation
| Visit* | Combined data | HMP 1 | HMP 2 | HMP 3 | HMP 4 | |||||
| 1 | 2 | 1 | 2 | 1 | 2 | 1 | 2 | 1 | 2 | |
| No of paired datasets (total paired sample time hour:min) | 74 380:20 | 20 97:57 | 14 70:57 | 22 125:50 | 18 85:36 | |||||
| Mean sample time (hour:min) | 5:08 | 4:54 | 5:04 | 5:43 | 4:45 | |||||
| Range of sampling start times (hour:min) | 8:16–10:22 14:38–18:00 | 8:16– 9:02 14:57– 18:00 | 8:52– 9:22 15:39– 15:54 | 8:42–9:57 14:38–16:14 | 9:08–10:20 15:22–16:29 | |||||
| Arithmetic mean (and 1 min range) of PM₂.₅ concentrations (µg/mᶟ) | 39 (0–1359) | 13 (0–3073) | 66 (2–678) | 14 (0–635) | 13 (0–121) | 6 (0–30) | 35 (0–1359) | 15 (2–227) | 36 (1–1058) | 17 (0–3073) |
| Arithmetic mean percentage reduction from pre-implementation to post-implementation | 66% | 79% | 50% | 58% | 54% | |||||
| Median (and IQR) of PM₂.₅ concentrations (µg/mᶟ) | 26 (15–46) | 8 (4–15) | 42 (27–76) | 8 (4–16) | 11 (6–17) | 6 (2–9) | 27 (17–44) | 9 (5–17) | 29 (18–44.5) | 8 (4–18) |
| Median percentage reduction from pre-implementation to post-implementation | 69% | 81% | 45% | 67% | 72% | |||||
| Percentage of time above 25 µg/mᶟ† | 51% | 11% | 77% | 13% | 7% | 0% | 53% | 14% | 56% | 15% |
*Visit number, 1=pre-smoke-free policy implementation, 2=post-smoke-free policy implementation.
†WHO 24 hour mean PM₂.₅ upper limit of 25 µg/mᶟ.
HMP, Her Majesty’s Prison.