EN 12845 Annex G — Wooden Cask Spirit Storage

A whisky bond house fire is among the fastest-spreading industrial fires there is — oak casks burst, 60 % alcohol turns into a pool fire, and plain sprinkler water cannot calm it. Annex G answers with AR-AFFF foam, a bund, ventilation and strict stack limits.

The best-documented cases come from bourbon and whisky maturation warehouses, where millions of litres of spirit in oak casks have burned for days, with flame visible for kilometres. Sprinklers were present in several of those cases, but they were standard systems rather than alcohol-resistant foam — and in an alcohol fire ordinary foam simply collapses. That scale is unusual in Turkey, but a wine cask store, a grape spirit plant or a pharmaceutical company's ethanol stock falls into exactly the same class. Annex G describes a risk that already exists; ignoring it is expensive.

Product and classification

Product	Alcohol (%)	Flash point (°C)	Class
Wine (red or white)	10–15	about 50	Class II
Sparkling wine	11–13	about 52	Class II
Sherry or port	15–22	about 38	Class IC
Cognac or brandy (new make)	40–55	about 26	Class IC
Whisky (cask strength)	50–65	about 22	Class IB
Raw spirit	65–95	about 12	Class IB
Pure ethanol	96+	13	Class IB

Annex G rules for wooden casks

• Block stacking limited to three tiers (about 3.6 m)
• 1.2 m aisles between stacks
• Above 50 000 L of stock: a separate REI 60 compartment
• Above 200 000 L: a standalone building
• A racked bond house of six to eight tiers: in-rack at every level plus ESFR at ceiling
• Design basis: 12.5 mm/min over 360 m² with 3 % AR-AFFF for 90 min
• Typical stored water at least 540 m³

AR-AFFF proportioning

• Bladder tank or balanced pressure proportioner
• Concentration of 3 % (common) or 6 %
• Concentrate tank sized for 90 min: 90 × 6000 × 0.03 = 16 200 L
• Tank protection against ethanol vapour back-flow
• A test line, for a functional proportioning test every three months
• EN 1568-3 certification for polar solvents
• Migration to fluorine-free (F3) alcohol-resistant foam is a live priority through 2025–2030

Bunding and drainage

To contain fire water and any alcohol pool, the bund is sized at 110 % of the largest stack volume plus 30 min of sprinkler discharge. For example, 50 casks at 500 L gives 25 000 L, so 27 500 L at 110 %; sprinklers at 12.5 mm/min over 360 m² for 30 min add 135 000 L. That is roughly a 163 m³ bund. Build it with a concrete kerb, an epoxy membrane and an oil-water separator. Drainage must not go to the normal sewer but to a controlled area — the mixture of water, alcohol and foam is an environmental pollutant.

Ventilation and explosive atmospheres

Oak casks continuously give up the "angel's share" — roughly 2 % of the ethanol evaporates each year. A million-litre stock therefore releases around 20 000 L into the air annually. In an enclosed bond house, ethanol concentration near floor level can exceed the lower explosive limit of about 3.3 %.

• At least 4 air changes per hour by mechanical ventilation
• Gas detection at low level, with an ethanol or LEL probe
• Explosion-protected lighting, switchgear and motors (ATEX Zone 1 assessment)
• Static earthing of forklifts, doors and racking
• Absolute ban on smoking, naked flame and hot work
• Emergency roof venting, to control oxygen supply during a fire

Field error — a wine cask store left on OH3

A wine producer stored 1500 oak casks racked to 4 m with standard OH3 sprinklers on conventional AFFF. The insurer's audit recorded that a Class II content at 12–14 % alcohol does not itself demand alcohol-resistant foam, but that a 4 m stack height makes in-rack protection mandatory. The missing in-rack lines were installed and the foam changed to a fluorine-free product. Even at low alcohol content, cask stack height alone triggers the Annex G in-rack requirement.

The racked, multi-tier bond house

A traditional bond house runs six to eight tiers with a 12–15 m ceiling and holds 5000 to 50 000 casks. Annex G applies its strictest design to this configuration:

• Ceiling ESFR K360 at 5.2 bar
• In-rack K115 at 3 bar on every level
• AR-AFFF concentrate typically 30 000–50 000 L
• Perimeter monitors at all four corners
• Gas detection every 50 m²
• Emergency venting at roof and side walls
• Fire service inlet connections
• An annual drill including a live foam test

Water and foam demand

A typical bond house of 10 000 casks over 5000 m²: ceiling ESFR twelve heads at K360 and 5.2 bar gives about 9800 L/min; in-rack thirty heads at 80 L/min adds 2400 L/min; four monitors at 2000 L/min add 8000 L/min; hose reels add 1000 L/min — roughly 21 000 L/min in total. Over 60 min that is 1260 m³ of water, plus about 38 000 L of concentrate at 3 % proportioning. That demand will strain a small town main, so a dedicated reservoir and pump station is mandatory.

Comparison with NFPA 13 and FM Global

NFPA 13 has no separate heading for wooden casks; the storage is interpreted under Class II and IIIA combustible liquids together with Group A plastics. FM Global's beverage storage data sheet is the most comprehensive source, making 12.5 mm/min plus AR-AFFF plus monitors the standard for a bond house. International spirits producers with Turkish supply chains work to NFPA 13 plus the FM Global data sheet, while Annex G is generally accepted for domestic producers.

Turkish regulation and local practice

BYKHY's flammable liquid storage limits require a separate building for Class IB above 1000 L. A bond house sits far above that threshold, so the insurer, the fire service and the environmental authority all assess it — potentially within the Seveso framework. Wine producers, spirit stocks and pharmaceutical ethanol stores in Turkey all fall within Annex G, and duty-free spirit warehouses carry additional specific regulation.

Quick check list

• Alcohol concentration and class established.
• Alcohol-resistant (polar solvent) foam selected.
• Concentrate sized for 90 min duration.
• Bund sized for spill plus 30 min of sprinkler discharge.
• Stacks limited to three tiers, or in-rack at every level.
• At least 4 air changes per hour.
• ATEX zone assessment and explosion-protected installation.
• Low-level gas detection.
• Static earthing on all metal equipment.
• Perimeter monitors and fire service inlets.
• A migration plan to fluorine-free foam.

Frequently Asked Questions

Why does ordinary AFFF fail on a spirit fire?

Because alcohol is a polar solvent that breaks down a conventional foam blanket. Alcohol-resistant AR-AFFF certified to EN 1568-3 is required, and fluorine-free equivalents are now the migration target.

How is the bund sized?

At 110 % of the largest stack volume plus 30 min of sprinkler discharge. For a modest cask block that is typically well over 100 m³, and the discharge must go to a controlled area, not the sewer.

What is the "angel's share" risk?

Around 2 % of the ethanol evaporates each year through the oak. In an enclosed bond house this can push floor-level vapour above the lower explosive limit, so mechanical ventilation and gas detection are needed.

Does low-alcohol wine need special treatment?

The foam requirement eases, but stack height alone still triggers Annex G: casks racked above about 3.6 m require in-rack protection regardless of alcohol content.

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