Depending on the total volume of stored material and the size of individual containers, NFPA 30 (or an AHJ) might classifiy the location Division 2. See the "Notes" at the end of Section 500.5(B)(2). However, as general rule, the location would be unclassified.
NOTE: Transfer of materials would indicate Division 1. See Section 500.5 (B)(1) "Note", No.1 (1). Lack of transfer does not automatically indicate "unclassified."
Robert B. Alexander, P.E.
Answers based on 2014 NEC unless otherwise noted.