Apparently someone thought the industrial looking unmarked air sensor in the Union Square subway station looked like an art installation on loan from a museum. All that was missing was the museum plaque with a title and esoteric description:
If You See Something, Say Something
Unidentified large vibrating metal object (with vent) on heavily populated Union Square subway station concourse
On loan from Free Admission exhibits, 2011
Citizens Police extensively trained by the Department of Homeland Security’s advertising campaign, wander past this extremely suspicious device with occasional and momentary curiosity.
Unmarked, unmanned, and unfriendly, it provides an excellent source of fear, thanks to its menacing appearance and complete lack of explanation.
Apparently this is part of a series of “art” pieces from Free Admissions Exhibits