I was coming back from vacation yesterday and connecting in Miami. When going through security in concourse A, there was a separate line of people going through a different machine. It was a booth that closed at one end and lit up with green and red lights, directing passengers how far to walk into the booth, and then to stop. Glass doors closed in front of them, and I could hear hydraulic air "whoosh" while the passenger was standing inside.

I don't know if people in that line had to go through the regular metal detectors in addition to this machine or not. Can anybody tell me what it was?

Thanks!

I went through one of those two weeks ago. It's basically checking for any signs of explosives. After this machine, I went through the standard metal detectors.

They have a couple of these at San Juan airport. They are cropping up all over the place.

Thanks! Is it a random check for people to go through? Or was it just in a preliminary testing mode before being put to use for all passengers?

It's a variety of the puffer box already in service for SSSS at numerous airports.

It's not "random" but rather the luck of the draw as to which security line you happen to be on - some have it, some don't. You go through the standard metal detector afterwards.