Manual security check, security gate, luggage machine... don’t think it’s troublesome, these security checks are different!

The holidays are approaching, and during the Spring Festival travel rush we need to go through heavy security checks wherever we go.

Seeing the long queue that seems to have no end, we can't help but wonder, what are the differences between manual security checks, security check gates, and luggage machines? Can't they be combined for inspection?

Handheld security scanners and security gates are used to check passengers, while luggage machines are used to check luggage. They have different functions and principles.

Security door

The security gate is the one we pass through the most. It uses the principle of electromagnetic induction to detect whether you are carrying metal objects on your body, so the security gate is essentially a metal detector.

Its working principle can be briefly described as follows: sensors are installed on both sides of the security door, which can emit and receive alternating electromagnetic fields. When a metal object approaches the magnetic field, it will affect the distribution of the magnetic field, causing the magnetic flux within this range to change. The change in magnetic flux will generate current, which will trigger an alarm.

Non-professionals please see the following cartoon:

Manual security check

The manual security check made me feel that I was being treated with care. The handheld security checker also uses the electromagnetic induction principle. However, the manual check is more detailed and can accurately detect the location of metal objects.

For example, during security checks in examination rooms, if a candidate carries metal objects on him/her, once the alarm sounds, it will be clear where the illegal equipment is hidden.

Some friends may have questions. It seems that there is always a sound when passing through the security gate?

Indeed, as long as there are metal products on your body, the security gate will make a sound. When the metal content is low, the alarm is small; when the metal content reaches a certain level, the alarm will increase, prompting security personnel to conduct further inspection.

Baggage security machine

The principle of the baggage security inspection machine is much simpler and more crude.

It uses the X-rays that we often hear about, which is a type of electromagnetic wave with a very short wavelength. One of its characteristics is that it can penetrate objects that are invisible to the naked eye, and its penetrating ability is different for different objects.

For example, the X-ray examination we do in the hospital is based on the different penetration rates of X-rays into muscles and bones, so we can clearly see the bone structure.

The same goes for luggage items; when your suitcase passes through the security scanner, the outlines of different objects will be displayed under the X-ray.

If you have seen the computer screen of the security personnel, you should have found that the X-ray film of the luggage is different from the X-ray film during the physical examination. The X-ray film of the luggage is in color, which is the result of computer calculation.

Different penetration intensities will be converted into different colors to help security personnel identify what the object is, such as orange for liquid and blue for metal.

By analogy, the security inspection machine can also be used in this way.

Human body X-ray security inspection

X-rays are not so friendly to the human body, but X-ray security checks are within a safe range and are mostly used for highly suspicious persons or criminal suspects.

X-ray vehicle inspection

Used for border inspection, public security departments, etc.

After all, with so much electromagnetic radiation, will it cause harm to the human body?

The answer is: as long as you lead a normal life and do not exceed the usage limit, it will not cause harm to your body.

Unless, like this...

Security gates and handheld security devices will not harm your health. They, like electric lights, telephones, induction cookers, etc., all use the principle of magnetic induction and have no ionizing radiation.

The X-rays in the baggage security scanner may endanger human safety, but they require a very large amount of measurement. The country has regulations on the annual cumulative exposure measurement of ordinary people to X-rays.

How is this measurement achieved?

Suppose you are a model worker who works 365 days a year.

The job is to be a subway security inspector for 8 hours.

The radiation dose that year was equivalent to 24 two-hour flights;

Assuming you are a successful business person,

Take 24 two-hour flights a year.

This amount of radiation is less than a chest X-ray;

Suppose you need to have 5 chest X-rays a year.

This amount of radiation is equivalent to a head CT scan;

A head CT scan just reaches the annual radiation dose stipulated by the state.

Within one year

National regulations on daily radiation dose

(8 hours of security check for 365 days) multiplied by 7

167 flights (two hours each)

5 chest X-rays

A head CT scan

However, medical radiation is generally not included in daily radiation dose. We can undergo medical examinations involving radiation less frequently when necessary, but we cannot give up medical treatment for fear of radiation.

If you don't believe in rumors, your life will be safe.

Of course, if you are a pregnant woman, theoretically you need to have 500 chest X-rays to cross the red line of fetal malformation.

However, when traveling, security inspectors will generally be considerate of the feelings of expectant mothers. If they request not to go through the security check gate, pregnant women can switch to manual inspection.

Security checks also include explosion-proof checks, which use particle mobility spectrometry technology to detect whether passengers have come into contact with explosives using cards;

Liquid inspection, through the heat conduction method: under the same heating conditions and time, the temperature difference is used to determine the thermal conductivity and thus the type of liquid;

As for drug inspections, drug detection dogs are not black technology, but they are very efficient. We should not tease them or interfere with their work just because they look good.

Finally, I would like to remind everyone not to be pessimistic when going out during the New Year!

Cherishing life and doing a good job of security checks are the real ways to ensure safety!

The Chinese New Year is coming soon, and it is time for relatives who have been away for a year to return home. Countless passenger flow peaks are gathered together, all of which are the wanderers' anticipation for home. Amidst the waiting, crowding, and carrying things on shoulders and in hands, the festive atmosphere gradually becomes dense, and the longing becomes stronger and stronger.

I would like to thank all the police, security personnel, technical support personnel, and flight attendants who have worked hard for the Spring Festival travel rush...

I also thank myself for my hard work throughout the year.

I wish you who are on your way home safely!

This article comes from: China Digital Science and Technology Museum