Methods we use to detect clandestine entrants

This page explains the methods our immigration officers use at sea ports to find people who are hidden inside vehicles coming to the United Kingdom from mainland Europe.

For information on the fines drivers and companies may have to pay for carrying these clandestine entrants into the United Kingdom, see What vehicle operators must do to prevent clandestine entrants.

Body detection dogs

Body detection dogs are trained to smell humans who are inside vehicles simply by sniffing the air outside the vehicle. The dog walks around the outside of the vehicle, sniffing the air that escapes from any gaps. If it does not smell any people inside, it will walk away. If it does smell people inside, it will react, for example by barking. The dog handler then knows that people may be inside the vehicle and will ask for the doors to be opened so that the dog can thoroughly search inside.

Gamma scanners

The gamma scanner is a mobile system, mounted on a lorry, that uses gamma rays to produce pictures of the contents of vehicles and containers. Without entering the vehicle or container, it can detect people and smuggled goods inside.

If a vehicle is chosen to be searched in this way, it is driven to the scanning area. The driver and any passengers are asked to stay in a waiting room. The gamma-ray scanner is then driven along the length of the vehicle.

The scan takes about a minute and produces an image on a monitor in the scanner's cab. A trained officer interprets the image and will decide whether any further action is necessary.

Heartbeat detector sheds

Although this system is usually called the heartbeat detector shed, it does not actually detect a person's heartbeat. The large sheds contain a mobile computer system that uses four special vibration sensors to detect movement inside a vehicle.

The movement causes tiny vibrations in any surfaces or objects the person is in contact with, and these are felt by the sensors placed on the body of the vehicle. The computer analyses the signals and can detect a hidden person within seconds. The results tell the operator whether to pass or search the vehicle.

Passive millimetric imaging

The passive millimetric wave imager makes use of the natural radiation, known as background radiation, that is always present in the air around us. It also uses a method of detecting heat and creating an image from it. The system does not create any radiation itself.

The imager uses a large reflector on one side of the vehicle being inspected, with a machine on the other side that creates the image. The background radiation bounces off the reflector and goes through the vehicle to a receiver in the imaging machine.

The machine converts it into a clear image of the contents of the vehicle that is displayed on a monitor.

Carbon dioxide probes

The carbon dioxide probe is a thin, lightweight tube attached to a monitor small enough to hold in a hand. It is designed to detect carbon dioxide, which is the gas our lungs breathe out. Carbon dioxide levels increase inside a closed vehicle when people are inside, and the monitor can detect this.

We use three types of probe:

• a one-metre aluminium tube with holes at the end that can be inserted into heavy goods vehicles with soft sides by pushing the tube through the gap between the vehicle's side and the canvas;
• a 25cm aluminium spike that can be inserted between the rubber seals of the back doors on a heavy goods vehicle with hard sides; and
• a thin tube made of carbon that uses magnets to attach to the air vents of a refrigerated heavy goods vehicle.

Once the probe is inserted into the vehicle, the monitor shows the level of carbon dioxide inside within 20 seconds.