A method of protecting commodities stored in a plurality of adjoining racks, having a vertical flue space provided between a set of racks of the plurality of adjoining racks, includes covering a rack, of the plurality of adjoining racks, and the vertical flue space with one or more solid horizontal barriers provided at a predetermined height. Each solid horizontal barrier has a width that is at least equal to a width of the rack and a depth that is at least equal to a sum of a depth of the rack and a depth of the vertical flue space. The method also includes providing one or more rack-level fire protection sprinklers in the vertical flue space below a solid horizontal barrier, of the one or more solid horizontal barriers, each rack-level sprinkler being vertically spaced from the commodities stored on the rack that is covered by the solid horizontal barrier.