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

1. 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, that is adjacent to the rack, 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, the at least one rack level 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) 1/2 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.

2. The fire protection sprinkler system according to claim 1 , wherein the predetermined height of the at least one horizontal barrier is between 10 feet and 30 feet (3.05 meters and 9.14 meters).

3. The fire protection sprinkler system according to claim 1 , wherein the at least one rack level sprinkler is one of (a) an extended coverage sprinkler, (b) a storage sprinkler, or (c) an extended coverage storage sprinkler.

4. The fire protection sprinkler system according to claim 1 , wherein the at least one rack level sprinkler includes two or more rack level sprinklers that are arranged in a row at a horizontal spacing of at least about 8 feet (2.44 meters).

5. The fire protection sprinkler system according to claim 1 , wherein the at least one rack level sprinkler is provided at a center of a length of each rack, of the plurality of adjoining racks.

6. The fire protection sprinkler system according to claim 1 , wherein each of the at least one rack level fire protection sprinkler comprises:

(i) a body having (1) an inlet connected to the fluid supply conduit within the vertical flue space, and (2) an outlet defining an outlet orifice;

(ii) a seal cap that seals the outlet orifice;

(iii) a frame extending from the body;

(iv) a deflector connected to the frame; and

(v) a thermally responsive element supported between the seal cap and the frame, the thermally responsive element urging the seal cap that seals the outlet orifice when the at least one rack level sprinkler is in an inactivated state,

wherein, when the predetermined height at which the at least one horizontal barrier is provided is up to about 30 feet (9.14 meters) and the at least one rack level sprinkler is positioned in the vertical flue space between the stored commodities and the at least one horizontal barrier, the at least one rack level sprinkler delivers the fire protection fluid over the stored commodities when the at least one rack level sprinkler is in an activated state.

7. The fire protection sprinkler system according to claim 1 , wherein the fluid supply conduit is disposed at or above a rack support frame of the plurality of adjoining racks that is adjacent to the fluid supply conduit.

8. The fire protection sprinkler system according to claim 1 , wherein each of the at least one rack level sprinkler comprises:

(i) a frame; and

(ii) a deflector connected to the frame,

wherein only the deflector of each of the at least one rack level sprinkler protrudes below a rack support frame of the plurality of adjoining racks that is adjacent to the fluid supply conduit.

9. The fire protection sprinkler system according to claim 1 , wherein each of the at least one rack level sprinkler is one of a pendent type sprinkler or a horizontal sidewall sprinkler.

10. The fire protection sprinkler system according to claim 1 , wherein the K-factor of the at least one rack level sprinkler is 25.2 gpm/(psi) 1/2 .

11. The fire protection sprinkler system according to claim 10 , wherein the fluid supply conduit delivers the fire protection fluid to the at least one rack level sprinkler at a minimum pressure of about 7 psig (48.26 kPa).

12. The fire protection sprinkler system according to claim 11 , wherein the at least one rack level sprinkler includes at least two rack level sprinklers, and the K-factor of each of the at least two rack level sprinklers is selected based on a proximity of each of the at least two rack level sprinklers to a severe fire hazard, the K-factor being a constant.

13. The fire protection sprinkler system according to claim 1 , wherein the at least one rack level sprinkler includes at least two rack level sprinklers, and the K-factor of each of the at least two rack level sprinklers is selected based on a proximity of each of the at least two rack level sprinklers to a severe fire hazard, the K-factor being a constant.

14. The fire protection sprinkler system according to claim 13 , wherein, the K-factor is selected such that the greater a height at which a rack level sprinkler, of the at least two rack level sprinklers, the greater the K-factor of the rack level sprinkler.

15. The fire protection sprinkler system according to claim 13 , wherein, the K-factor is selected such that the greater a height at which a rack level sprinkler, of the at least two rack level sprinklers, the lower the K-factor of the rack level sprinkler.

16. The fire protection sprinkler system according to claim 1 , further comprising (D) at least one ceiling level fire protection sprinkler provided above the at least one horizontal barrier.

17. The fire protection sprinkler system according to claim 16 , wherein the at least one ceiling level sprinkler is one of (a) an extended coverage sprinkler, (b) a special application sprinkler, (c) an early suppression fast response sprinkler, (d) a storage sprinkler, or (e) an extended coverage storage sprinkler.

18. The fire protection sprinkler system according to claim 16 , wherein the at least one rack level sprinkler and the at least one ceiling level sprinkler are the same type of sprinkler.

19. The fire protection sprinkler system according to claim 16 , wherein a K-factor of the at least one ceiling level sprinkler is about 11.2 gpm/(psi) 1/2 or greater.

20. The fire protection sprinkler system according to claim 19 , wherein the K-factor of the at least one ceiling level sprinkler is about 25 gpm/(psi) 1/2 or greater.