ASRS Fire Suppression: How to Design Fire Protection Into an Automated Warehouse

Codes and approvals: who decides what protection an ASRS needs

No single national organization approves every U.S. warehouse installation. NFPA writes the standards, including NFPA 13 for sprinkler systems, NFPA 25 for inspection and maintenance and NFPA 72 for alarms and signaling. A standard becomes enforceable when a jurisdiction adopts it. The International Code Council publishes the International Fire Code, and IFC Chapter 32 covers high-piled combustible storage, with Section 3209 on automated storage in the 2024 edition.

FM adds property-loss-prevention guidance, including Data Sheet 8-34 for automatic storage and retrieval systems. It is insurer guidance rather than municipal law, but it can become a project requirement through the owner's insurance. The authority having jurisdiction (AHJ), which may be a fire marshal or a building official, enforces the adopted codes locally and rules on alternative methods.

Recommended engagement sequence

1. Confirm the jurisdiction, the adopted fire and building codes and editions, and the designated AHJ.
2. Share the ASRS concept, storage dimensions, commodities, container materials and access arrangement with the AHJ, owner, insurer and fire protection engineer.
3. Agree on the protection basis (prescriptive design or a proposed alternative) and on which FM recommendations or insurer conditions apply.
4. Decide whether full-scale or commodity-specific fire-test evidence and third-party review are required.
5. Submit coordinated drawings, calculations, equipment interfaces, emergency procedures and permit documents.
6. Confirm witnessed acceptance testing, ongoing inspection plans and the change-management process for stored products and equipment.

How sprinkler protection works, and why water penetration is the test

An automatic sprinkler is a heat-activated device that opens on its own when the temperature near it passes a set threshold. The system works as a sequence: a fire makes heat, the heat opens sprinklers, and enough water reaches the burning commodity to control or suppress the fire. Warehouse systems are designed around commodity classification, packaging materials, storage height, rack configuration, building height and available water supply. The higher the hazard of the stored material, the more water the design has to deliver.

Sprinkler discharge by K-factor at 50 psi operating pressure. A different operating pressure changes the flow.

A K33.6 sprinkler discharges about six times the water of a K5.6 at the same pressure. That spread is why commodity hazard drives so much of the design.

Where traditional ASRS design interferes with sprinklers

Sprinklers work only if two things happen. Heat has to reach the sprinkler quickly, and water has to reach the fire after the sprinkler opens. Open racks with adequate flue spaces support both. Dense automated storage often does not.

The paper calls loss of flue space one of the most significant fire protection challenges in ASRS installations. Reduced flue space can delay heat reaching the ceiling, slow sprinkler activation, limit water penetration and allow a fire to grow out of sight.

Container choice matters as much. Plastic totes release heat faster than corrugated cardboard, and solid-bottom totes can fill with sprinkler water instead of passing it to the levels below. Perforated totes can help water drain through, but hole size, spacing, nesting, alignment between levels and the contents of the tote all change how much water gets down. The paper cautions against assuming that perforations justify reduced sprinkler criteria without test evidence the AHJ and the insurer accept.

Shelving, trays and shuttle rails can block discharge. Cranes, shuttles, conveyors and power rails add obstructions and possible ignition sources. Narrow aisles and enclosed racks limit what firefighters can reach, so the suppression system often has to achieve a higher degree of fire control before anyone can step in.

Six sprinkler types, and the cost of putting them inside the rack

Most warehouses rely on ceiling-mounted sprinklers. As tote-based stacking gets taller and denser, fire protection engineers may add in-rack sprinklers to put water directly into the storage array. The paper compares six types.

Design recommendations: build fire protection in before the layout is final

The paper's recommendations all land in the same place. Fire protection goes into the engineering phase, before the ASRS layout is finalized, because decisions on products stored, system geometry, existing building details and tote design change both the complexity and the cost of the protection.

1. Preserve the paths that water and heat need. Heat has to travel up and water has to travel down, so flue spaces, rack depth and shelf construction belong in the design review from the start.
2. Limit combustible components. The container is often a bigger contributor to fire severity than the product, so evaluate material, total plastic content and open versus enclosed geometry.
3. Use fire-resistant storage containers where they fit. Building protection into the container reduces reliance on building infrastructure.
4. Design for ceiling-only protection whenever practical. Lower the storage height, keep flue spaces, limit rack depth and cut plastic fuel load before turning to extensive in-rack systems.
5. Tie the controls system to the fire alarm. On activation, the warehouse control system should stop robot movement, isolate affected zones, remove power, park shuttles and cranes in safe locations, give the fire department access and identify the affected inventory.
6. Layer the protection so no single measure carries the whole load.

The paper uses the Attabotics Guardian Bin as its example of building protection into the container. A conventional plastic tote can add fuel to a fire. The Guardian Bin is designed to isolate and contain fire at the source, limiting oxygen and reducing spread to adjacent storage locations, so a fire stays in one location while the suppression system has time to act.