As the high-density storage unit for the University Library, Oak Street Library has the unique role of maximizing preservation of the items it houses while simultaneously shelving them strategically to ensure the least amount of storage space is wasted. The vaults that house UIUC collection are climate controlled by state-of-the-art hvac system to guarantee the ideal temperature and humidity level for maintaining the structural integrity of print resources (about 50° Fahrenheit and 30% humidity respectively). Once items are sent to Oak Street Library, they are sorted and separated by size to assure an efficient use of space. Featuring a super-flat concrete floor structure, this facility is one of only few globally.

As of 2017, more than four million items are stored at the Oak Street Library Facility.