Denver International Airport uses many pneumatic tube systems, including a 25 cm diameter system for moving aircraft parts to remote concourses, a 10 cm system for United Airlines ticketing, and a robust system in the parking toll collection system with an outlet at every booth.
Note: No citation, and I can't find any reference to it on the web.
Question: If these systems actually exist, what are their total lengthes (eg. 35 km total) and usage rate (eg. 7000 objects per day)?