The phrase "open vents" means to allow air to flow through small openings or channels in order to ventilate and circulate the air inside a space. Full definition
Alternatively, you can manually release the pressure by opening the vent; again the silver indicator will go down when pressure has been relieved. (thefamilythathealstogether.com)
I love this tie up shirt with open vents — the perfect stylish summer piece. (harperandharley.com)
Gone are the twin opening vents beneath the windshield and the dash's utter simplicity in favor of a «fully integrated» fascia. (automobilemag.com)