What happened at the airport security check?

Almost a month ago I was traveling with Pegasus airlines and I had a few hours transit through SAW airport, when the plane arrived I have to go through a security checkpoint before heading to the transit area, I placed my backpack, my phone my watch my belt and everything I had on me, so I was left with nothing but only clothes with no metals, but once I crossed the metal detector machine (security gate) it beeped, which was very weird, they checked me with the scanner first, found nothing suspicious, but then they took a small white piece of paper and swapped my palms with it and checked it on a machine which gave a green sign and she said it's fine. But honestly to this day I don't understand what happened?! Why did the detector gate beep and why they had to wipe my palms, I'm extremely curious about it. Can anyone elaborate me and tell me what exactly happened? I would be so grateful

They wiped your palms to check for explosive residue. Some machines beep to indicate that a random search is called for. That might have been the case here, and why you were wanded and wiped.

Probably to make sure you didn't have anything you shouldnt have had, i go thru the same thing cause of hip implants

Its looking for residue from explosive type material, it can be done randomly even without gate beeping, they can also wipe your carryon

It was signalling the security personnel to let them know that you needed to be randomly selected for additional screening. Some x-ray machines are programmed to signal random people so that the security personnel can't be accused of racial profiling if they were the ones picking people for random additional screening.

Just by the way, your hands were not 'swapped' but 'swabbed'.

You have selected a best answer, but I will answer anyways. (SAW airport… Flying out of Turkey.)

This is similar to what happens in the US The metal detector has a function to select passengers for random screenings. The number of which is determined by security officials. As such you were selected. When selected you go through any one of procedures for additional screening. As such you were selected for a random screening.

"small white piece of paper and swapped my palms with it and checked it on a machine"

That is referred to as an ETD (Explosive Trace Detection) machine. What it does is the swab picks up minute particulates from your hand and sent to the machine for analysis for the potential presence of explosives. (It is similar to the high pressure liquid chromatograph except it uses dry air as the medium.)

My recommendation is to expect random screenings to happen.