The Bureau of Prisons operates institutions of five different security levels (i.e., minimum, low, medium, high, and administrative). Security levels are based on such features as the presence of external patrols, towers, security barriers, or detection devices; the type of housing within the institution; internal security features; and the staff-to-inmate ratio.
Types of Bureau of Prison Facilities
The following is a brief description of BOP facilities, see U.S. Department of Justice, Bureau of Prisons, Prison Types & General Information (details available here):
Minimum Security Bureau of Prisons Facilities
Also known as Federal Prison Camps (FPCs), these facilities have dormitory housing, a relatively low staff-to-inmate ratio, and little to no perimeter fencing. They are work- and program-oriented; and many are located adjacent to larger institutions or on military bases, where inmates help serve the labor needs of the larger institution or base.
Low Security Bureau of Prisons Facilities
Federal Correctional Institutions (FCIs) with double-fenced perimeters, typically dormitory or cubicle housing, and strong work and program components. The staff-to-inmate ratio in these institutions is higher than in minimum security facilities.
Medium Security Bureau of Prisons Facilities
FCIs (and U.S. Penitentiaries (USPs) designated as medium security) with strengthened perimeters, such as double fences with electronic detection systems, largely cell-type housing, a wide variety of work and treatment programs, a higher staff-to-inmate ratio than low security FCIs, and even greater internal controls. Note there are no Medium security level institutions for female inmates.
High Security Bureau of Prisons Facilities
USPs with highly-secured perimeters (featuring walls or reinforced fences), multiple- and single-occupant cell housing, the highest staff-to-inmate ratio, and close control of inmate movement.
Administrative Bureau of Prisons Facilities
Administrative BoP facilities have special missions, such as the detention of pretrial offenders; the treatment of inmates with serious or chronic medical problems; or the containment of extremely dangerous, violent, or escape-prone inmates. Administrative facilities include Metropolitan Correctional Centers (MCCs), Metropolitan Detention Centers (MDCs), Federal Detention Centers (FDCs), and Federal Medical Centers (FMCs), as well as the Federal Transfer Center (FTC), the Medical Center for Federal Prisoners (MCFP), and the Administrative-Maximum (ADX) U.S. Penitentiary. Administrative facilities are capable of holding inmates in all security categories.