Fire protection in automated warehouses: the insurer writes the criterion

In February 2019 a fire knocked out the automated grid warehouse of a large British online grocer in Andover, southern England, a site handling 30,000 orders a week. The investigation carried out by the company with its insurers and the Hampshire fire service, reported by Reuters two months later, traced the cause to an electrical fault at a first-generation battery charging unit at the edge of the grid. The fault set the plastic lid of a robot on fire. In July 2021 the same group had a second fire at another site, in Erith, after three robots collided on the grid. This time, according to the company's statement, damage was limited to "less than 1%" of the grid and contained by planned fire attenuation measures, with sprinklers activated and nobody hurt.

The second figure comes from the party concerned and should be read as such. Even so, the gap between the two outcomes is the best argument available on a question that is almost never heard in negotiations: who established how the system you are about to buy is protected against fire, and on what test evidence. In compact automated warehouses the answer surprises people used to conventional racking, because the criterion is not found in the robot's standard and only partly in the sprinkler rules.

The robot's CE marking stops at the robot

An autonomous vehicle arrives with its declaration of conformity. Since May 2024 the standard supporting its presumption of conformity in Europe has been EN ISO 3691-4:2023, added to the harmonized standards by Commission Implementing Decision (EU) 2024/1329. Its title states its subject: safety requirements and verification for driverless industrial trucks and their systems. It concerns the safety of the machine toward people. How to put out a fire inside a storage block several meters high, full of plastic containers and with no aisles, is a matter for the building, the goods and whoever insures them.

This is why a supplier can present fully compliant machines and a system for which nobody has yet defined the protection. The two run on separate tracks, and the second often starts late, when the layout is already fixed and every change is expensive.

Why the rules for conventional racking fall short

Sprinkler systems in conventional warehouses are designed around known configurations: racks with aisles, vertical gaps between loads that let heat rise and water come down, classified heights and commodities. A compact system removes exactly those gaps to gain density. Two fire protection engineers at Jensen Hughes, Anthony Rago and Moriel Kaplan, put it plainly in an August 2022 analysis. NFPA 13, the US reference standard for sprinklers, provides options for standard storage configurations but no specific protection requirements for compact ASRS projects, meaning high-density automated storage and retrieval systems.

The document that does contain them is an insurer's data sheet, FM Global Data Sheet 8-34, and the same authors point out its limit: it provides sprinkler design criteria only for compact systems tested by the insurer. For all others the work is based on the manufacturer's test data, with a warning to take care when designing to third-party data or extrapolating from it. In practice the criteria are set by the insurer and the owner, in coordination with the fire service that would have to respond.

What Data Sheet 8-34 covers, and where it says it has no answer

The document, in its July 2017 edition with an interim revision in July 2024, runs to 119 pages, and its scope separates three families of system. The first groups horizontal-loading systems, mini-load and shuttle, with small containers or trays. The second is the top-loading grid, which the text defines by how it works: containers are loaded and unloaded vertically by robots moving on an elevated gridded track network, with no aisles. The third covers vertically enclosed systems.

Then comes the sentence that makes the whole document worth reading. Some configurations are declared outside its scope and, for now, without any known protection options. They include open-top containers with a gridded rather than solid bottom, in both horizontal and top-loading systems, and expanded plastic trays or containers. An insurer writing that it knows of no way to protect a given combination is a rare piece of information. It turns the type of tote from a supply detail into a design variable, because it decides whether the system can be protected under a published criterion or not.

The robots are part of the fire design too

The least expected part of the data sheet concerns the machines. Section 2.3.3.1 asks for robots to carry as little exterior combustible material as possible, and for covers and identification, where needed, to be noncombustible. The next section asks for holding areas to be defined on the grid, where all robots go when fire detection activates, never above the grid access points and with the columns below kept free of combustible goods. These areas are not required if noncombustible, solid-walled containers are used throughout the grid.

Two requirements for the building complete the picture. Ceiling-level detection must be of the very early warning type approved by the insurer. Where possible, the perimeter should have a curb at least 100 mm high with drainage sized for the sprinkler discharge plus 1,900 liters per minute for manual firefighting. A layout designer needs these numbers before drawing the slab, because curbs and drainage cannot be added once the system is installed.

Read next to the account of the two fires, these sections touch the same points: exterior materials on robots, early detection, charging areas. After Andover the company said it had removed the plastic lids from its robots and added localized smoke detectors. A causal reading that the facts do not support should be avoided, though. The first edition of the data sheet predates the first fire, and no public source says what was or was not applied at that site. What the two episodes show is simpler: the risk sat in components nobody thinks of as part of fire protection, a charger and a lid.

Who decides in Italy

A US insurer's data sheet is not law in Italy, and neither is NFPA 13, now in its 2025 edition. The mandatory framework is national fire prevention. Storage buildings over 1,000 square meters holding more than 5,000 kilograms of combustible materials fall among the activities subject to fire service control listed in Presidential Decree 151/2011. Design follows the Fire Prevention Code set out in the Ministerial Decree of August 3, 2015, and sprinkler systems are normally designed to EN 12845, adopted in Italy as UNI EN 12845:2026, which transposes EN 12845:2015+A2:2026 and replaced the 2020 edition. The Code allows alternative solutions alongside the prescriptive ones, provided the designer demonstrates their effectiveness. That is the route a system outside the tabulated cases almost always ends up taking.

That demonstration is where test data becomes decisive again. The fire engineer signing the design needs to know which configuration the system was tested in, with which containers and with what result. The insurer of the building and the goods will ask the same questions before quoting the policy. It pays to put them in the purchase specification, while the supplier still has an interest in answering in full. The assessment itself rests with the appointed designer and the competent fire authority. What follows is meant to give them what they need to work with.

Six questions to put in the specification before the quotation

• Fire testing: has the system been tested in the configuration offered? By which laboratory or insurer, and is the report available?
• Containers: material, solid or gridded walls and bottom, open or closed top. Does the configuration fall under a published protection criterion?
• Robots: what combustible materials they carry on the outside, and what they do on a fire alarm.
• Charging: where the stations are in relation to storage, how they are monitored and which battery chemistry is used.
• Detection and suppression: what detection is planned inside and above the block, what discharge density, what access for manual firefighting.
• Civil works: curbs, drainage and compartmentation required by the chosen criterion, and who pays for them.

A supplier that has dealt with the subject replies within days and attaches documents. Generic answers on this point are as useful a signal as a throughput figure, and they arrive sooner.

Where the problem shrinks, and where it does not

Automated warehouses do not all raise the question in the same way. When mobile robots serve shelving with aisles, or move pallets between conventional racks, storage stays closer to the configurations sprinkler rules already know, and fire design starts from familiar ground. Closer does not mean identical: heights, density, packaging and the position of charging areas still need checking, and on charging the subject overlaps with station sizing for AMR fleets. For a small system holding noncombustible goods the whole analysis may come down to a few checks. It grows with density, with plastic and with the value of what is inside.

One general rule remains, useful to anyone comparing different automated warehouse solutions. Fire protection belongs in the comparison from the start, on a par with throughput and footprint, because it can change the tote, the layout and in some cases the technology. For anyone assessing a goods-to-person system or a fleet of mobile robots, the fire question therefore comes before the choice of tote.

What to send us for an assessment

To prepare with you the fire questions to attach to the request for quotation, so that your designer and your insurer have the answers before you sign, we need the following:

• an outline layout of the automated storage, with heights and its position in the building;
• the technology under assessment: top-loading grid, mini-load, shuttle, mobile shelves or a robot fleet;
• type of goods and packaging, with the share of plastics and foams;
• planned containers: material, solid or gridded walls and bottom, open or closed top;
• existing fire protection and the building's insurer, if already known;
• planned position of the charging stations and battery chemistry.

You can send them by email to info@pitech-solution.com or on WhatsApp. The assessment on the merits remains with your fire engineer and the competent fire authority.