In one arrangement, a storage system for storing items includes an enclosure enclosing a hypoxic environment, and a pallet shuttle system comprising rows of racks disposed within the hypoxic environment. The pallet shuttle system also includes at least one transfer car and at least one shuttle for carrying storage modules into and out of the racks. The system further includes a loading station outside the hypoxic environment, and an enclosure door to the hypoxic environment. The enclosure door is operable to admit the transfer car of the pallet shuttle system into and out of the hypoxic environment, and to close the hypoxic environment upon passage of the transfer car through the door. Optionally, the system includes paneling separating the enclosure into at least two separately climate-controlled zones such that at least one of the racks is in each of the at least two separately climate-controlled zones.