MONITORING PLACES OF DETENTION : A PRACTICAL GUIDE 69 sample of the persons held there, and to examine the facilities and living conditions. The length of the visit should also, however, reflect the fact that visits can disrupt or inhibit the work of the staff in charge of the persons deprived of their liberty. It is thus important to strike a balance between the need for efficient monitoring and the constraints inherent in the way such places function. The length of the visit can be estimated on the basis of the following factors: ■ the size of the visiting team; ■ how much is already known about the places to be visited: - Has the mechanism already visited the place? - Has it received information from third parties which helps it to estimate the time needed for the visit? ■ the size of the place of detention and the number of persons held there; ■ the type of place of detention; - the security regimes applied (the higher the security, the longer it can take to move about within the detention facility); - Are there different categories of persons deprived of their liberty under different detention regimes held in the same place? This can mean that more time is needed to examine the different conditions of detention; ■ the staffing or institutional conditions; ■ the languages spoken by detainees and the possible need for interpretation; ■ the work needed to compile the data, which must be done as quickly as possible at the end of the visit;