food of nutritional value adequate for health and strength, of wholesome quality and well prepared and served. 2. Drinking water shall be available to every prisoner whenever he needs it. European Prison Rules [Recommendation Rec(2006)2 of the Committee of Ministers to member states on the European Prison Rules] Rule 18.1 The accommodation provided for prisoners, and in particular all sleeping accommodation, shall respect human dignity and, as far as possible, privacy, and meet the requirements of health and hygiene, due regard being paid to climatic conditions and especially to floor space, cubic content of air, lighting, heating and ventilation. Rule 18.2 In all buildings where prisoners are required to live, work or congregate: a. the windows shall be large enough to enable the prisoners to read or work by natural light in normal conditions and shall allow the entrance of fresh air except where there is an adequate air conditioning system; b. artificial light shall satisfy recognised technical standards; c. there shall be an alarm system that enables prisoners to contact the staff without delay. Rule 18.10 Accommodation of all prisoners shall be in conditions with the least restrictive security arrangements compatible with the risk of their escaping or harming themselves or others. Rule 19.3 Prisoners shall have ready access to sanitary facilities that are hygienic and respect privacy. Rule 22.1 Prisoners shall be provided with a nutritious diet that takes into account their age, health, physical condition, religion, culture and the nature of their work. 2. The requirements of a nutritious diet, including its minimum energy and protein content, shall be prescribed in national law. 3. Food shall be prepared and served hygienically. 4. There shall be three meals a day with reasonable intervals between them. 5. Clean drinking water shall be available to prisoners at all times. 2nd General Report of CPT [CPT/Inf (92)3] § 49 Ready access to proper toilet facilities and the maintenance of good standards of hygiene are essential components of a humane environment. In this connection, the CPT must state that it does not like the practice found in certain countries of prisoners discharging human waste in buckets in their cells (which are subsequently "slopped out" at appointed times). Either a toilet facility should be located in cellular accommodation (preferably in a sanitary annex) or means should exist enabling prisoners who need to use a toilet facility to be released from their cells without undue delay at all times (including at night). 11th General Report of CPT [CPT/Inf (2001)16] § 30 The CPT frequently encounters devices, such as metal shutters, slats, or plates fitted to cell windows, which deprive prisoners of access to natural light and prevent fresh air from entering the accommodation. They are a particularly common feature of establishments holding pre-trial prisoners. The CPT fully accepts that specific security measures designed to prevent the risk of collusion and/or criminal activities may well be required in respect of certain prisoners. However, the imposition of measures of this kind should be the exception rather than the rule. This implies that the relevant authorities must examine the case of each prisoner in order to ascertain whether specific security measures are really justified in his/her case. Further, even when such measures are required, they should never involve depriving the prisoners concerned of natural light and fresh air. The latter are basic elements of life which every prisoner is entitled to enjoy. Moreover, the absence of these elements generates conditions favourable to the spread of diseases and in particular tuberculosis.