EN 12845 Annex G — Flammable Liquid Storage

A flammable liquid fire is not afraid of water; throw water on it and the flame spreads, and the fire area grows. Annex G makes sprinklers plus AFFF foam plus bunding mandatory for flammable liquid storage. The Class I/II/III split and the flash point are the foundation of the design.

A chemical supplier's warehouse held 80 IBCs of acetone — flash point −20 °C, Class IA — under standard OH3 water-only sprinklers. One IBC ignited from a static spark. The sprinklers operated, water fell onto the acetone, and since acetone floats it burned on the surface and spread the fire to 600 m² within four minutes. The water then carried acetone leaking from the IBCs across the floor and, with no bund in place, out under the door onto the road. Annex G is explicit: Class I means AFFF foam, bunding and limited stock. Sprinklers alone are not a design.

Flammable liquid classification

Class	Flash point (°C)	Typical product	Sprinkler strategy
IA	< 23 (boiling < 38)	Ether, propylene oxide	AFFF, bund and monitors
IB	< 23 (boiling ≥ 38)	Acetone, petrol, ethanol	AFFF foam-water
IC	23–38	Thinners, xylene	AFFF foam-water
II	38–60	Diesel, kerosene, paraffin	AFFF or high-density water
IIIA	60–93	Motor oil, fuel oil	High-density water (CMDA)
IIIB	> 93	Vegetable oil	Water (HHS)

Design densities

Class	Water density	Foam proportion	Area	Duration
IA–IB	10 mm/min	3 % AFFF or 1 % fluorine-free	260 m²	60 min
IC–II	8 mm/min	3 % AFFF	260 m²	60 min
IIIA	10 mm/min	Case by case	260 m²	90 min
IIIB	7.5 mm/min	None	260 m²	90 min

The foam-water sprinkler system

The sprinkler discharges water pre-mixed with AFFF concentrate; the foam blankets the liquid surface and cuts off oxygen. The components:

• Foam tank (atmospheric or bladder type; around 10 000 L is typical at 3 %)
• Proportioner: bladder tank, balanced pressure or in-line eductor
• Deluge valve, since the system usually runs dry with open heads
• Detection: fire panel plus flame and heat detectors
• Open sprinklers or foam-water applicators
• A test line for proving the foam with a substitute liquid

IBC and drum stacking rules

• IBCs (1000 L plastic): maximum 2 tiers, about 3.6 m
• Drums (200 L steel): maximum 3 tiers, about 3.6 m
• 1.2 m aisles between stacks
• Above 50 000 L: a separate compartment with REI 60 walls
• Above 200 000 L: a standalone building
• A 0.1 m threshold at doorways, to keep spillage inside the bund

The bund

Bund capacity is 110 % of the largest single container plus 30 min of sprinkler discharge over the design area. For example, one 1000 L IBC gives 1100 L at 110 %; sprinklers at 10 mm/min over 260 m² for 30 min add 78 000 L. That gives a 79.1 m³ bund. In practice 25 % of total stock is accepted as the alternative basis, and the larger of the two governs.

• Concrete kerb 0.3–0.5 m high
• Impermeable lining (epoxy or polyethylene membrane)
• Separate rainwater drainage through an oil-water separator
• Fire water must not enter the normal drain; discharge is controlled
• A ramp or threshold at access points

The move away from PFAS foams

Traditional C8 AFFF contains PFAS and is being restricted across the EU between 2025 and 2030 under REACH. EN 12845 accepts fluorine-free (F3) foams. The migration sequence:

• Empty the existing tank — specialist disposal, and expensive
• Wash the tank and pipework, circulating water three to five times
• Reset the proportioning rate; F3 products often run at 1–3 % rather than 3 %
• Buy a certified F3 product (EN 1568, UL 162, ISO 7203)
• Functional test the system for expansion ratio and drainage time
• Notify the insurer and the fire service

Field error — machine oil treated as OH3

A textile machinery parts warehouse stored lubricating oil with a 95 °C flash point (Class IIIA) in 200 L drums. The designer proposed OH3 at 5 mm/min on the assumption that oil is harmless. The insurer's audit recorded that Annex G requires 10 mm/min over 90 min for Class IIIA — a doubling of density. Even Class III liquids demand a high water density, because once a fire takes hold the oil mass reaches 700–900 °C and many sprinklers operate. The rule that flammable liquid means high density is unconditional.

Monitors and large-fire protection

Above 50 000 L of stock, sprinklers alone are not sufficient and perimeter monitors are added:

• Fixed or manually directed
• 2000–10 000 L/min depending on nozzle size
• Integrated foam concentrate proportioning
• Manual or remote control
• Spaced 30–50 m apart around the perimeter
• Located beside the fire service inlet connections

Comparison with NFPA 30 and FM Global

NFPA 30, the Flammable and Combustible Liquids Code, is the comprehensive counterpart to Annex G. NFPA limits Class IA and IB to a single tier (1.8 m) where Annex G accepts two. FM Global's data sheet on flammable liquid storage in portable containers gives detailed stack geometry, bunding and foam design. Refining and petrochemical facilities in Turkey work to NFPA 30 with the FM data sheet, while Annex G is sufficient for a smaller chemical supplier.

Turkish regulation and local practice

BYKHY devotes several clauses to flammable liquid storage, covering stock limits, bunding, ventilation and ATEX zoning, and directs sprinkler design to Annex G or NFPA 30. The Seveso III framework requires a risk assessment for stocks above 50 000 L. Annex G is the working fire protection standard in Turkey's chemical industrial zones.

Quick check list

• Products classified from their safety data sheets (Class IA to IIIB).
• Design density matches the class.
• AFFF or F3 foam provided for Class I and II.
• Bund capacity calculated.
• Stack heights within limits (IBCs 2 tiers, drums 3).
• Compartment walls where stock exceeds 50 000 L.
• Monitors provided above 50 000 L.
• A migration plan to fluorine-free foam.
• Seveso notification made where applicable.
• ATEX zone assessment and explosion-protected installation.

Frequently Asked Questions

Why can water make a flammable liquid fire worse?

Because most flammable liquids float on water. Sprinkler water spreads burning liquid across the floor rather than cooling it, which is why a foam blanket is essential for Class I and II.

How is the bund sized?

110 % of the largest single container plus 30 min of sprinkler discharge over the design area — or 25 % of total stock, whichever is greater.

How high can IBCs and drums be stacked?

Two tiers for 1000 L plastic IBCs and three tiers for 200 L steel drums, roughly 3.6 m in both cases, with 1.2 m aisles between stacks.

What is changing with AFFF?

PFAS-containing C8 foams are being restricted across the EU between 2025 and 2030 under REACH. Migration to certified fluorine-free F3 foam requires tank cleaning, re-proportioning and a functional retest.

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