REST (Remote Explosive Scent Tracing) is a method of detecting explosive vapours. Consignments for REST must be isolated, completely wrapped and stood for a minimum period of two hours. Several air samples are then removed from various parts of the shipment by means of a portable vacuumed pump through a filter.
Filters are then transported to a separate location (analysis room) and placed in a stand under controlled conditions away from the consignment and interrogated by an explosives Dog. If the shipments are cleared the Agent will receive a statement from the REST operator claiming the shipment to be free from explosives.
The legislation states that all cargo loaded onto a passenger-carrying aircraft must undergo one of the approved methods of security screening. These are:
(a) Known Consignor Procedures
(b) screening by X-Ray (the primary method of screening)
(c) physical examination including searching by hand (primary screening method)
(d) Remote Explosive Scent Tracing (REST) formally known as Air Sampling Canine Olfaction (RASCO ) (secondary screening method)
Cargo which has undergone one of these procedures can then be classified as SPX cargo (cargo that has been screened to enable it to be transported on any type of aircraft).