Locker doors usually have some kind of ventilation to provide for the flow of air to aid in cleanliness. These vents usually take the form of a series of horizontal angled slats at the top and bottom of the door, although sometimes parallel rows of small square or rectangular holes are found instead, running up and down the door. Less often, the side or rear walls may also have similar ventilation.
There is a luggage storage service a short one minute walk from Union Station in downtown Denver - LUGDEN. You can make a reservation online - lugden.com, call - (303) 747-5600, or show up as a walk-in. They offer hourly, day, overnight and weekly bag storage. Great place to store your luggage if you're on a layover from Denver International Airport, or going to a concert, or headed to a Rockies game at Coors field and want to enjoy yourself without having to lug your bags around.