VACIS stands for Vehicle and Cargo Inspection System. It is a non-intrusive inspection (NII) system that uses gamma-ray imaging to inspect cargo containers without breaking the seal.
(CBP) to inspect cargo for illegal drugs, weapons, and other contraband. VACIS is used by U.S. Customs and Border Protection
VACIS exams are typically conducted at the port of entry, but they can also be conducted at inland locations. The exam process begins when the cargo container is placed on a VACIS scanner.
The scanner emits a low-level beam of gamma rays that passes through the container. The gamma rays are then converted into digital images that can be viewed by CBP officers.

CBP officers use the VACIS images to identify any anomalies that may indicate the presence of contraband.
 If an anomaly is detected, the CBP officer may request a physical inspection of the cargo container. Physical inspections are conducted by CBP officers who are specially trained to detect contraband.

VACIS exams are an important part of CBP's efforts to protect the United States from illegal drugs, weapons, and other contraband.
VACIS exams have been shown to be very effective at detecting contraband, and they have helped to keep dangerous materials out of the United States.
Here are some additional details about VACIS exams:

VACIS exams are typically conducted within 48 hours of the cargo's arrival at the port of entry.
The exam process typically takes about 30 minutes.
VACIS exams are free of charge.
There is no way to know for sure if your cargo will be selected for a VACIS exam. However, there are some factors that may increase the likelihood of your cargo being selected, such as the type of cargo you are shipping, the country of origin, and the port of entry.
If your cargo is selected for a VACIS exam, you will be notified by the CBP officer.
You will not be able to access your cargo during the exam process.
If contraband is detected during a VACIS exam, the CBP officer may seize the cargo and take further action.
If you have any questions about VACIS exams, please contact the CBP office at the port of entry where your cargo is being shipped.