Prisons and remand centres are encouraged by government to minimise the potential ingress of drugs narcotics. In many such facilities, the threat from illicit materials being thrown over the perimeter wall has been largely mitigated with increased perimeter patrols and fence-line monitoring techniques. The majority of drugs narcotics, discovered in prisons and remand centres, are largely illegally imported by visitors to the inmates.
Based on either intelligence information, behavioural monitoring or by random selection, visitors to such centres can be screened to detect whether they have been in contact with drugs narcotics. This is achieved by the use of sample swabs or vapour detection techniques.