Automated Storage and Retrieval Systems (AS/RS) are accelerating warehouse operations, enabling unprecedented speed and density. But these gains come with a tradeoff: the more tightly engineered the storage grid becomes, the further it drifts from the fire protection assumptions that warehouse codes were built on. Facilities adopting automation are operating in a fire environment that traditional suppression strategies were never designed to handle.

The Ocado Warehouse Fire, Andover UK

In 2019, a major fire at Ocado’s Andover facility illustrated the fire protection challenges inherent in robotic storage grids. An electrical fault in a battery charging unit ignited a robot, and the fire quickly spread within the dense storage structure. The large amount of stored goods provided ample fuel, resulting in a fire that lasted for days.

Why the Fire Protection System Failed to Control the Fire

Ceiling-level sprinklers were unable to reach the seat of the fire because of the physical conditions inside the AS/RS grid:

Delayed sprinkler activation: Smoke and heat were trapped within the grid, slowing heat transfer to ceiling sprinklers and allowing the fire to grow unchecked.

Shielded ignition point: The fire started deep within a compact grid of plastic totes, rails, and structural components, preventing sprinkler water from reaching and cooling the core.

Blocked water penetration: The dense geometry acted as a physical barrier, stopping ceiling sprinklers from delivering water into the ignition zone.

Vertical heat channeling: Tight spacing between bins created a chimney-like path that accelerated upward heat and flame spread.

The incident was not a failure of individual equipment, it was a fundamental mismatch between traditional sprinkler design and the physical geometry of high-density automated storage. This event drove a global reassessment of fire protection strategies for AS/RS installations.

The Hazards of AS/RS and Robotic Warehousing Systems

The conditions that allowed the Ocado fire to grow so rapidly aren’t unique to that facility. They reflect fundamental characteristics of AS/RS and robotic warehousing that complicate detection, suppression, and sprinkler performance. The following hazards represent the underlying engineering challenges that arise across high-density automated systems.

Extreme Storage Density

AS/RS grids eliminate the vertical and horizontal flues that traditional sprinkler design relies on. Solid totes, rails, and robot components block heat movement and water penetration, allowing fires to grow unseen.

Lithium-Ion Battery Risks

Robotic shuttles rely on lithium-ion batteries, which can malfunction or enter thermal runaway during charging and heavy cycling. Off-gassing, intense heat, and ignition of surrounding plastics make battery failures a leading ignition source.

High Fire Load

Fire load comes from more than packaging. Stored goods, polymer totes, plastic housings, and structural components all contribute to high heat release rates, often with Group A commodity behavior.

Distributed Ignition Points

Motors, sensors, wiring, and batteries are embedded throughout the grid, creating ignition sources deep within the structure where suppression is least effective.

Shielding and Heat Build-Up

Compartmentalized totes and the dense geometry trap heat at the ignition point, enabling temperatures to rise long before detection or suppression occurs.

Delayed Detection

Restricted airflow slows smoke movement, meaning a fire can grow significantly before ceiling-level detection or sprinklers activate.

Fast Lateral Fire Spread

Once ignition occurs, flames can move horizontally through tightly packed totes and compartments, spreading more rapidly than in conventional racking systems.

A Turning Point: AS/RS Fires Exposed Major Gaps

Catastrophic fires in AS/RS facilities exposed gaps in traditional warehousing guidance. NFPA 13’s assumptions—open-rack storage, open flue spaces, and unobstructed sprinkler discharge—do not align with the physical realities of dense automation.

Why Traditional Code Assumptions Don’t Apply

• Loss of Flue Spaces: The cube-like geometry of tightly packed plastic totes eliminates the vertical and horizontal flues needed for heat transport and water distribution.
• Water Penetration Limits: Overhead sprinklers cannot reach a fire shielded deep within a grid of totes, rails, and robot pathways. The result is a hidden fire that can grow unchecked inside the structure.

These factors create a technical disconnect: evaluating AS/RS facilities under standards written for open-rack storage leaves critical hazards unaddressed.

How Fire Protection Strategies Are Shifting

Catastrophic fires in AS/RS facilities exposed gaps in traditional warehousing guidance. NFPA 13’s assumptions of open-rack storage, open flue spaces, and unobstructed sprinkler discharge, do not align with the physical realities of dense automation.

These factors create a technical disconnect: evaluating AS/RS facilities under standards written for open-rack storage leaves critical hazards unaddressed

Warehouse Fire Trends

In the U.S., total warehouse fires are far lower today than they were in 1980, but that long-term decline has flattened. Since 2011, NFPA data shows a gradual upward trend of roughly 2% per year. Between 2016 and 2024, U.S. warehouses saw nearly 1,500 fires annually, resulting in 2 deaths, 16 injuries, and more than $1 billion in property damage each year.

Warehouses now store larger volumes of goods, a wider range of commodities, and far more combustible materials than in past decades. The rapid expansion of the logistics sector means more warehouses are being built, more goods are stored, and more operations run around the clock, all of which increase the overall likelihood of fire incidents.

But newer technologies are also reshaping the fire landscape. The adoption of AS/RS automation and the widespread use of lithium-ion batteries in robotics and material-handling equipment introduce concentrated ignition sources and distinct fire dynamics. Together, these factors point to a growing need for more advanced, system-specific fire protection strategies for modern warehouse and AS/RS environments.

Aligning Fire Protection With the Realities of Modern Warehouses

To navigate the complex landscape of AS/RS fire protection, RAN Fire Protection Engineering brings deep technical expertise and decades of applied project experience. Our engineers design robust, code-compliant fire protection systems built around the actual geometry and operating conditions of automated warehouses—not theoretical assumptions. From shielding challenges to lithium-ion hazards, we help clients understand their risks and implement reliable, system-specific solutions. Protect your facility and your inventory with fire protection engineering built for today’s automated warehouse environment.

Learn more about our specialized warehouse fire safety projects: RAN Fire Protection Engineering Warehouse Projects.