FM Global DS 8-34: Mini-Load ASRS Design

A mini-load ASRS is a horizontal-loading automated store in which a picking robot in the aisle places and retrieves small containers and trays. FM Global DS 8-34 (July 2017, interim revision April 2026) treats mini-load separately from shuttle systems: closed-top noncombustible containers are covered in Section 2.2.5, closed-top combustible containers and trays in 2.2.6, and open-top combustible containers in 2.2.7. For the rules that apply to every ASRS type, see the DS 8-34 overview.

Mini-Load Rack Configuration

• Containers or trays sit on angle irons, which divert most of the sprinkler discharge to the rack face and reduce the water reaching the flue spaces. This is what sets mini-load apart for protection purposes (3.1.1, Appendix A).
• Rack uprights are about 50 to 75 mm in section and 450 to 600 mm apart along the aisle; tier heights are usually 225 to 400 mm (3.1.1, Appendix A).
• Containers are typically unexpanded plastic and usually open-top, although noncombustible, cardboard and expanded plastic containers are also used (3.1.1).
• Aisles are usually at least about 0.8 m wide, and some systems are rack-supported structures that carry the building and can be very tall (3.1.1).
• Expanded plastic containers and trays are outside the scope of DS 8-34 (1.0).

When Is Ceiling-Only Protection Possible?

• Closed-top, noncombustible, solid-walled containers used throughout: sprinkler protection is designed for the surrounding occupancy hazard (2.2.5.1).
• Closed-top combustible containers or trays: ceiling-only protection is possible where the flue spaces meet 2.2.1.4, aisles are at least 1.1 m wide (1.2 m where the ceiling exceeds 9.1 m or uncartoned expanded plastics are stored), uncartoned plastics are not stored directly on the rails, and Tables 2.2.6.1.2(a) to 2.2.6.1.2(d) offer an option (2.2.6.1.1). The wet-system table (Table 2.2.6.1.2(a)) gives options for ceilings up to 12.2 m.
• Open-top combustible containers: ceiling-only protection is possible only where storage does not exceed 3.0 m (2.2.7.1.1; Table 2.2.7.1.2(a) for wet systems, Table 2.2.7.1.2(b) for dry).

In-Rack Sprinkler Arrangement

• In-rack sprinklers are FM Approved, quick-response, 160°F (70°C) storage sprinklers (2.2.1.6.2.2).
• Closed-top combustible containers or trays: choose the horizontal arrangement from Table 2.2.6.2.1 (Figures 2.2.6.2.1(a) to (e); maximum horizontal spacing 1.5 m). For a wet in-rack system Table 2.2.6.2.2.1(a) allows a maximum vertical distance of 3.0 m (minimum K11.2 (K160) at 230 L/min) or 4.6 m (minimum K14.0 (K200) at 380 L/min), with no more than 3.0 m of storage above the top in-rack level (2.2.6.2.2.1). Dry in-rack systems use Tables 2.2.6.2.2.1(c) and (d).
• Open-top combustible containers: choose the horizontal arrangement from Table 2.2.7.2.1 (Figures 2.2.7.2.1(a) to (e); in-rack sprinklers at every other transverse flue space, with on-line spacing not exceeding 1.5 m). Table 2.2.7.2.2.1(a) allows a maximum vertical distance of 3.0 m (minimum K11.2 (K160) at 380 L/min) or, for some wet arrangements, 4.6 m (minimum K22.4 (K320) pendent at 530 L/min) (2.2.7.2).
• Where the vertical distance between tiers is less than 225 mm, add 75 L/min to the in-rack design flow; never use an in-rack design pressure below 0.5 bar (footnotes to Tables 2.2.6.2.2.1 and 2.2.7.2.2.1, 2.2.6.2.2.3, 2.2.7.2.2.3).
• Where transverse flue spaces between rack uprights have a gross width of at least 38 mm but material handling supports reduce their net width to 13 mm or less, and these flue spaces are more than 3.0 m apart, install vertical barriers of at least 0.7 mm sheet metal or 10 mm plywood at rack uprights no more than 3.7 m apart, and include every in-rack sprinkler between the barriers in the design (2.2.1.5, 2.2.6.2.2.4, 2.2.7.2.2.4, Appendix A).
• The ceiling design used with in-rack sprinklers comes from Tables 2.2.6.2.3.1 and 2.2.6.2.3.2 (closed-top) or Tables 2.2.7.2.3.1 and 2.2.7.2.3.2 (open-top) (2.2.6.2.3, 2.2.7.2.3).

Open-Top vs Closed-Top Containers

• Open-top: a container with walls higher than 25 mm that has no cover, or a cover that does not keep water out; it counts as open-top however full it is (Appendix A).
• Closed-top: a container with a solid cover that stays in place during a fire and keeps water out (Appendix A). Plastic containers with folding lids that do not seal completely should be treated as open-top (3.1.1.3).
• Cardboard containers: lower heat release than plastic, but easier ignition and faster burning (3.1.1.2).
• Water load: with open-top containers, design the racking, anchorage and floor for half of the containers below the in-rack sprinklers filling with water (2.1.2.5, 2.2.1.3.1).

Quick Checklist

• Rack confirmed as mini-load (angle-iron supports) per Appendix A
• Container material and open or closed top identified; no expanded plastic containers
• Transverse flue spaces measured against 2.2.1.4
• Ceiling-only conditions (2.2.6.1.1 or 2.2.7.1.1) checked
• Horizontal in-rack arrangement from Table 2.2.6.2.1 or 2.2.7.2.1; vertical distance and flow from Table 2.2.6.2.2.1 or 2.2.7.2.2.1
• Ceiling design with in-rack sprinklers from Tables 2.2.6.2.3.1–2.2.6.2.3.2 or 2.2.7.2.3.1–2.2.7.2.3.2
• Ceiling-level detection shuts down the robots; small hose stations provided

Frequently Asked Questions

Is ceiling-only protection enough for a mini-load ASRS?

It depends on the container. For closed-top combustible containers or trays it is enough where the flue spaces are adequate, aisles are at least 1.1 m wide (1.2 m where the ceiling exceeds 9.1 m or uncartoned expanded plastics are stored), uncartoned plastics are not stored directly on the rails, and Tables 2.2.6.1.2(a) to 2.2.6.1.2(d) offer an option (DS 8-34 2.2.6.1.1). With open-top combustible containers, ceiling-only protection is possible only where storage does not exceed 3.0 m (2.2.7.1.1).

How does a mini-load ASRS differ from a shuttle ASRS?

The difference is the rack support. In a mini-load rack the containers sit on angle irons that divert sprinkler discharge to the rack face, whereas in a shuttle system they rest on slatted or mesh shelving and water can reach the flue spaces (DS 8-34 3.1.1, Appendix A). That is why the two types use separate tables; height or load weight is not the distinguishing criterion.

How far apart vertically are the in-rack sprinkler levels?

For closed-top combustible containers or trays on a wet system, Table 2.2.6.2.2.1(a) allows a maximum of 3.0 m (minimum K11.2 at 230 L/min) or 4.6 m (minimum K14.0 at 380 L/min), with no more than 3.0 m of storage above the top in-rack level. For open-top containers, Table 2.2.7.2.2.1(a) allows a maximum of 3.0 m (minimum K11.2 at 380 L/min) or, for some wet arrangements, 4.6 m (minimum K22.4 at 530 L/min).

What does the mini-load robot do when a fire is detected?

DS 8-34 calls for an FM Approved ceiling-level fire detection system over horizontal-loading ASRS. On activation it must send an alarm to a constantly attended location and automatically shut down the robots (2.2.1.7.3). This detection is not needed where closed-top noncombustible containers are used throughout the array (2.2.1.7.4).

How are plastic containers classified?

DS 8-34 requires the design to be based on the more severe of the stored product and the container or tray material (2.1.3.1.3). Classification follows DS 8-1, and FM does not use the NFPA Group A/B/C plastics groupings. Unexpanded plastic containers are within scope; expanded plastic containers and trays are outside the scope of DS 8-34 (1.0).

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