Table 1.

Study prison characteristics and data collection dates

Prison	HMP 1	HMP 2	HMP 3	HMP 4
Category and function*	Male Category B Local	Male Category C Training	Male Category C Training	Male Category C Training
Structural design	Built 1850s Victorian radial design	Built early 1800s Singular wings	Built 1974 Five two story living blocks and quick build wings	Built 1960s Mix of triangular, T-shaped and quick build wings
No of wings	7	7	9	9†
Smoke-free implementation date	11/04/16	25/04/16	9/05/16	23/05/16
Prisoner roll count pre-policy	505	634	706	518
Prisoner roll count post-policy	477	628	691	378†
Sampling dates pre-policy	19/01/16 – 23/01/16	08/02/16 – 11/02/16	15/02/16 – 18/02/16	29/02/16 – 02/03/16
Sampling dates post-policy	05/07/16 – 08/07/16	18/07/16 – 21/07/16	22/08/16 – 25/08/16	15/08/16 – 17/08/16

*Category B prisons hold prisoners for whom the very highest conditions of security are not necessary but for whom escape must be made very difficult. Category C prisons hold prisoners who cannot be trusted in open conditions but who do not have the resources and will to make a determined escape attempt. Local prisons serve the courts and receive remand and post-conviction prisoners prior to their allocation to other establishments. Training prisons hold sentenced prisoners who tend to be employed in a variety of activities such as prison workshops, gardens and education and in offending behaviour programmes.

†HMP 4 closed two wings (and transferred all prisoners located on these wings) between pre- and post-smoke-free data sampling dates.

HMP, Her Majesty’s Prison.