If some extremely dangerous criminals are detained, they will be placed in a heavily guarded prison for solitary confinement (one cell for each person) to prevent them from hurting others and escaping. Prisons are divided into three categories: high security prisons, medium security prisons and low security prisons. The criminals held in different types of prisons are also different, as follows: 1, high-security prison: the main detention was sentenced to 65438+. Criminals, recidivists, recidivists who have been sentenced to life imprisonment or death penalty with a two-year suspension, criminals who have been sentenced to more than two punishments, or other criminals who have obvious personal dangers such as violence and escape tendency. 2. Medium-security prison: it mainly holds criminals whose sentence is less than 15 years. 3. Low-security prison: mainly for criminals with low personal danger. Including negligent offenders, occasional offenders, first-time offenders and other criminals who are considered suitable to serve their sentences in low-security prisons after classified investigation.