-34 The measures taken have to be necessary and proportionate in light of available alternatives, safeguards have to be available to the detainee, and the physical and mental health of the prisoner has to be assessed in order to ensure that they are compatible with his continued solitary confinement.68 As time passes, the motivations for the imposition of the measure have to be more detailed and compelling (see also CPT69),the decision on the prolongation of the measure has to consider any changes in the prisoner’s circumstances, situation or behaviour, and the detainee’s physical and mental health should be regularly monitored in order to ensure that his condition is compatible with continued solitary confinement.70 The lack of a specific maximum number of days in the ECtHR standards (which found no violation of Art. 3 of the ECHR even for year-long solitary confinement) is one of the problematic issues encountered by NPMs when advocating with the authorities for the reduction of the time spent in isolation by detainees. Another critical point is represented by the fact that ECtHR measures social isolation taking into account other elements other than human interaction, which is the most important element in order to maintain a good state of mental health. Since the 2020 version of the EPR states that all separated detainees should get at least two hours of meaningful social contact, the ECtHR could consider this as a new standard to evaluate the level of social isolation of the prisoner. 3.4 Material conditions and regime All cells, including those for solitary confinement, should be large enough for single occupancy (around 6 square meters according to the CPT and the ECtHR) with a window allowing in the cell natural light and air, and provided with artificial light, (EPR71, CPT72, ECtHR73). The placement of detainees in cells without lights, windows or ventilation (HRC74) or in a 68. European Court of Human Rights, Case of Öcalan v. Turkey (No. 2), §§138-140. 69. European Committee for the Prevention of Torture, 2011, §§56-57. 70. European Court of Human Rights, Case of Ramirez Sanchez v. France, §§136-139. 71. EPR 18.1. 72. European Committee for the Prevention of Torture, 2011, §§58-60 73. European Court of Human Rights, Case of Ramirez Sanchez v. France, §§12, 127, 130. 74. Human Rights Committee, Report of the Human Rights Committee. Volume I, A/56/40, New York, 2001, §78(14)