If you’re pulled out Reagan National Airport security lines for further screening, you’ll probably undergo an additional examination. National is a test stie for a Transportation Security Administration program where boarding passes will be examined for explosives residue, the Post reports.

If passengers set off the metal detector or if they have been preselected for additional scrutiny, a security screener will rub both sides of the passenger’s boarding pass across a small piece of cotton gauze attached to the machine.

The screener then pushes a button and the gauze slides into the machine to be analyzed. Within seconds, a small color screen displays whether the material contains traces of explosives. The machines cost $40,000 to $50,000 each …

While it doesn’t seem this should add any significant time to passing through DCA security, its better to be safe than sorry. DCist says try to factor a few minutes extra into your airport logistics planning.

Photo of DCA from spaceimaging.com