I am an architect for a local fire district for which we are building a new fire house. In addition to the new fire house they are also wanting to construct a separate 3 story burn tower for training purposes fabricated from used shipping containers. The structure has been designed and fabricated separately by a national company that has built several of these throughout the country and are familiar with the structural requirements. We have been asked by our client to assist burn tower fabricator in helping to secure a building permit for the structure. Because it is a 3 story structure the local AHJ is wanting justification for not enclosing the 3 story interior stairs or providing the required separation from the 3 story exterior stairs. I'm not sure how to respond to this request? Is this considered an "occupied" structure? If so, is it a "U" occupancy and how does that help? Any suggestions / help would be appreciated.