15 47. Police custody is (or at least should be) of relatively short duration. Nevertheless, conditions of detention in police cells must meet certain basic requirements. All police cells should be clean and of a reasonable size1 for the number of persons they are used to accommodate, and have adequate lighting (i.e. sufficient to read by, sleeping periods excluded) ; preferably cells should enjoy natural light. Further, cells should be equipped with a means of rest (e.g. a fixed chair or bench), and persons obliged to stay overnight in custody should be provided with a clean mattress and clean blankets. Persons in police custody should have access to a proper toilet facility under decent conditions, and be offered adequate means to wash themselves. They should have ready access to drinking water and be given food at appropriate times , including at least one full meal (i.e. something more substantial than a sandwich) every day. Persons held in police custody for 24 hours or more should, as far as possible , be offered outdoor exercise every day. Many police detention facilities visited by CPT delegations do not comply with these minimal standards. This is particularly detrimental for persons who subsequently appear before a judicial authority ; all too frequently persons are brought before a judge after spending one or more days in substandard and filthy cells, without having been offered appropriate rest and food and an opportunity to wash. 48. The duty of care which is owed by the police to persons in their custody includes the responsibility to ensure their safety and physical integrity. It follows that the proper monitoring of custody areas is an integral component of the duty of care assumed by the police. Appropriate steps must be taken to ensure that persons in police custody are always in a position to readily enter into contact with custodial staff. On a number of occasions CPT delegations have found that police cells were far removed from the offices or desks where police officers are normally present, and were also devoid of any means (e.g. a call system) enabling detained persons to attract the attention of a police officer. Under such conditions, there is considerable risk that incidents of various kinds (violence among detainees; suicide attempts; fires etc.) will not be responded to in good time. 1 (92) 3). As regards the size of police cells, see also paragraph 43 of the 2nd General Report (CPT/Inf