Vents are usually sewn shut with a little bit of string, like this:
Public Service Announcement: Don't forget to cut the strings to release the vent!
The strings are there to help the material lay flat and look nice on the hanger. Cut off the strings before you leave the house! I definitely have been guilty of walking around with my skirt vent sewn shut once or twice (as an intern! before I knew better!), but once I realized I had been walking around all day like that, I was embarrassed and quickly fixed the issue. I only bring this up because on Friday in court I saw 2 people in front of me in line to call a case - 1 man and 1 woman, who had the vents of their blazers still sewn shut. Congrats on the new suit, but don't let everyone know you got a new suit :)
There are a bagillion more "office faux-pas" that I can think of, but that may be another post for another time. For now, just remember to snip your strings :)