Table 2.
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.