How does the metal detector in airport functions?

Answer 1

A metal detector is really called a magnetometer (Magnet meter) .

A magnetometer produces a strong magnetic field. Any metal objects passing through the magnetic field will react with the magnetic field and begin to conduct a very slight electrical current. This process is called induction. These electrical currents cause their own much weaker magnetic fields. The magnetometer detects that new magnetic field and the interaction with the primary magnetic field it is producing. When the interaction reaches a certain per-determined threshold, the alarm is triggered. At this point officers will use hand-held magnetometers (known as wands) to pin-point the source of the alarm. The noise they make is an audible representation of the strength of the secondary magnetic fields produced by metal objects as the wand passes by.

Magnetometers can be so sensitive as to detect tooth fillings, titanium implants and other non-ferrous metals. Most metal detectors in airports are tuned so they are not triggered for tooth fillings or small metal implants like surgical pins. But they will be triggered by larger implants like knee replacements, hip implants, etc.

Contrary to folk lore, an airport magnetometer CAN detect non-ferrous (no iron, non magnetic) metals like titanium, brass and aluminum just fine. As long as the metal can conduct electricity (which is one of the properties of elements called metal) it can be detected by the device.

Anyone with a pacemaker should never go through the metal detector since the magnetic field can affect the electrical pulses generated by the pacemaker to keep the heart beating at a steady rate. Though highly unlikely, it is possible that a person with a pacemaker going though a magnetometer could go into cardiac arrest due to fibrillation. Simply tell the attendant that you have a pacemaker and they will do a hand search instead.

As long as it can conduct electricity it will be detected by a well-tuned magnetometer.