When space is expensive economics says to store product high, which is cheaper than expanding the warehouse out. This has led to some pallet storage at dizzying heights. For example, three stories is not unusual.
Automated storage and retrieval devices are generally used for dangerous heights but not always. We heard of an IBM site that relies on intrepid workers on person-aboard trucks that lift them high into the air. They are safely linked to their truck and so cannot fall; but the problem is how to get them down in case of accident. IBM requires that all order-pickers in this part of the warehouse be trained in rappelling!
