In-rack fire protection sprinkler system including at least one unitary horizontal barrier that covers racks of adjoining racks and at least one rack level fire protection sprinkler disposed below the at least one horizontal barrier

A fire protection sprinkler system for the protection of commodities including Class I-IV hazards, Group A cartoned and exposed plastics (expanded and unexpanded), flammable liquids, tires, roll paper, and aerosols, stored in a plurality of adjoining racks that have a vertical flue space provided between a set of racks of the plurality of adjoining racks, the system comprising:

• (A) a fluid supply conduit configured to deliver a fire protection fluid received from a fire protection fluid source;
• (B) at least one unitary horizontal barrier that covers (a) a rack, of the plurality of adjoining racks, (b) another rack, of the plurality of adjoining racks, and (c) the vertical flue space between the rack and the other rack, the at least one unitary horizontal barrier being provided at a predetermined height, and having a width that is at least equal to a width of the rack, and having a depth that is at least equal to a sum of (i) a depth of the rack, (ii) a depth of the other rack, and (iii) a depth of the vertical flue space;
• and
• (C) at least one rack level fire protection sprinkler connected to the fluid supply conduit to receive the fire protection fluid from the fluid supply conduit, the at least one rack level fire protection sprinkler (a) being disposed in the vertical flue space below the at least one horizontal barrier, (b) having a K-factor of 11.2 gpm/(psi)112 or greater, and (c) being vertically spaced from the commodities stored on the rack and the other rack covered by the at least one unitary horizontal barrier.