Generally speaking, when checking baggage packages in safe places such as airports and stations, the baggage x-ray security machine uses x-rays to scan the baggage. Usually, two x-ray beams with different intensities are used to illuminate the package at the same time, and with different densities and materials, the objects of x-ray diffraction and radiation will be different.

　　Therefore, as long as the staff sorts out the diffraction and transmission results of ordinary explosives and dangerous goods, and stores them in the computer, the suspicious objects encountered in the routine security inspection can only be checked by comparison with the image.
Generally, on the display screen of the x-ray security inspection machine, the greater the relative density of the blocks (such as metal materials), the longer the color tone, which will attract the special attention of safety inspectors. However, if the risk block (such as a firearm) is removed and combined with other metal material components (such as a notebook computer, camera) for hidden inspection, usually the security inspector must have sufficient experience and a high degree of expertise. Discover the degree of responsibility. At the same time, this method is very effective for solid materials (especially metals), but not for liquids.

Because most dangerous liquid x-rays are easy to pass, it is difficult to distinguish between gasoline and water. In this case, the most reliable method is sample analysis, which requires the passenger to open the bottle to remove the liquid for chemical or physical testing. However, if the bottle is not opened, unopened wine and medicine, etc., then other options must be considered. The principle of screening a bottle of liquid material is to start from the other side of the bottle and reflect off the wall of the bottle, and the effect of the liquid will change to identify a liquid different from the exposed particles. Electromagnetic waves that can perform this task include ultrasound, laser, microwave, infrared, etc. In different liquids, there are some differences in parameters, such as propagation speed, attenuation, scattering angle and transmittance. By comparing flammable, explosive and hazardous liquids, it can be determined whether the liquid is harmful.