EN 12845 Annex G — PP/PE Storage Bins

Plastic bins are spreading fast through logistics — more hygienic than timber pallets, washable and stackable. But in a fire they release three times the energy of a timber pallet and they melt and drip. Annex G calls for ESFR and tight stack limits for PP and PE storage bins.

At a food distribution warehouse, 8000 empty 60 L polypropylene bins had been stacked 4 m high as temporary storage during a production pause. The system was OH3. A forklift battery short-circuited and the spark reached the stack. The polypropylene melted at 165 °C, ran down onto the lower tiers and spread the fire to 1100 m² within six minutes. Sprinkler water spread the melt across the surface but could not extinguish it, and the roof collapsed after 28 minutes. Annex G limits empty PP bins to a 1.2 m stack — this was more than three times that. Logistics warehouses are more hazardous than they used to be, and the design has to keep pace.

Types of storage bin

Type	Volume	Material	Fire load
Stackable logistics bin	15–200 L	HDPE	High
Fruit and vegetable crate	10–30 L	PP	High
Laundry bin	200–500 L	HDPE	High
Industrial parts box	20–60 L	PP	High
Waste container	240–1100 L	HDPE	High
Wheeled refuse bin	120–240 L	HDPE	High

Annex G stack heights

Condition	Max. height	Design
Empty, unracked	1.2 m	12.5 mm/min over 360 m²
Empty, unracked	2.4 m	16.5 mm/min plus in-rack
Empty, racked	≤ 9 m	ESFR K360 at 5.2 bar
Empty, racked	Above 9 m	ESFR plus in-rack every 3 m
Full (food, components)	Depends on contents	Assessed as OH3 to HHS

Fire behaviour

• PP ignites around 340 °C; HDPE around 350 °C
• PP melts at 165 °C; HDPE at 130 °C
• Melting occurs well before ignition, so the dripping risk is high
• Calorific value around 46 MJ/kg — about 2.5 times timber
• Flame spread of roughly 1.5 to 2 times the stack height per minute
• Emissions of CO and CO₂; relatively clean compared with PVC, but still hazardous
• Molten material sticks to the floor and hardens as it cools

ESFR as the only practical design

For any empty PP or HDPE bin storage above 2.4 m, ESFR is effectively the only practical design:

• K360 (25 mm) at 5.2 bar — fast response, rapid suppression
• Spacing 3 × 3 m, coverage no more than 9 m²
• Deflector 0.15–0.4 m below the ceiling
• Roof slope no more than 5 %
• Skylights limited to 5 m², with ventilation controlled
• Strict obstruction rules
• Early operation — sprinklers within about 12 s, suppression within about 60 s
• EN 12845-2:2024 Annex P provides the detail

Field error — recycled HDPE waste containers

At a recycling facility, recycled HDPE waste containers (240 L wheeled bins) were stacked 6 m high in an open yard with no fire protection design at all. One season, extreme heat, direct sun, wind and static electricity combined to produce an ignition. The fire spread to the neighbouring facility. Annex G requires at least 8 m separation and a maximum 6 m stack height for outdoor storage. Open-air plastic storage is within the scope of Annex G; the assumption that "it's outdoors, so sprinklers are unnecessary" is wrong — fire service monitors, separation distances and seasonal precautions are all required.

Mixed stacks of bins and pallets

In practice plastic bins sit on timber pallets and are wrapped in stretch film. Annex G assesses that combination as Group A plastic, on the worst-case basis:

• Plastic bins on timber pallets: ESFR required
• Plastic bins on plastic pallets: ESFR plus in-rack
• Plastic bins inside cartons: the classification eases slightly, toward Group B
• Stretch-wrapped stacks: increased dripping risk

Passive measures

• Metal grating beneath stacks, to limit the spread of molten drips
• Concrete floor with a defined fall, to direct sprinkler water
• Absolute ban on smoking, heaters and other ignition sources
• Forklift battery charging at least 8 m away, in a separate room
• Monthly floor cleaning to prevent dust accumulation
• A hot work permit system
• Trained staff with a drill every six months
• External stacks at least 8 m from the facade
• Rainwater drainage through an oil-water separator, for fire water control

Worked water demand

ESFR K360 at 5.2 bar with twelve operating sprinklers: Q = 12 × 360 × √5.2 ≈ 9850 L/min. Over 60 min that is 591 m³, plus hose reels at 500 L/min for 60 min, i.e. 30 m³ — about 621 m³ of stored water in total. The pump needs at least 10 000 L/min at 6 bar to cover sprinklers, hoses and losses. That is roughly four times the tank of a standard OH3 warehouse; ESFR is expensive, but it is the only correct answer here.

Comparison with NFPA 13 and FM Global

NFPA 13's Group A plastic storage provisions make ESFR the standard for empty PP and HDPE bins, commonly K22 ESFR at 75 psi (5.2 bar). FM Global's commodity classification data sheet places plastic bins in the highest category. Plastic bin use is increasing across Turkish grocery retail logistics, and those facilities should be designed to NFPA 13 with the FM Global data sheet. OH3 is still encountered in domestic manufacturers' warehouses.

Turkish regulation and local practice

BYKHY gives no separate class for plastic bins; they fall under high-hazard storage. Insurers require compliance with Annex G or the FM Global commodity data sheet. ESFR design is becoming widespread in Turkey's food distribution hubs, and it is now standard for e-commerce warehouses where plastic bin use is heavy.

Quick check list

• Bin material identified as PP, HDPE or PE.
• Empty or full status classified.
• Stack height within the Annex G limit.
• ESFR planned above 2.4 m.
• Mixed pallet-and-bin stacks designed on the worst case.
• Protection against molten drips beneath the stack.
• Forklift charging area at least 8 m away.
• Monthly cleaning and inspection.
• External stacks at least 8 m from the facade, with rainwater drainage.
• ESFR tank sized for 60 min duration.

Frequently Asked Questions

How high may empty plastic bins be stacked?

1.2 m unracked at 12.5 mm/min, or 2.4 m at 16.5 mm/min with in-rack protection. Racked storage up to 9 m requires ESFR K360 at 5.2 bar.

Why is melting more dangerous than burning here?

Because PP melts at 165 °C and HDPE at 130 °C — well below their ignition temperatures. Molten material runs onto lower tiers and spreads the fire faster than flame alone would.

Are outdoor plastic bin stacks covered by Annex G?

Yes. Open-air storage still needs at least 8 m separation and a maximum 6 m stack height. "It's outdoors so sprinklers aren't needed" is not a valid conclusion.

What water demand does an ESFR bin store need?

Roughly 9850 L/min for twelve K360 heads at 5.2 bar, giving about 620 m³ of stored water including hose reels — some four times a standard OH3 warehouse.

SprinkCalc — Fire Sprinkler Design Across Three Standards

SprinkCalc covers hazard classification, design density and area, K-factor selection, water demand and hydraulic calculations for NFPA 13, FM Global and BS EN 12845 in a single iOS app, and exports a professional PDF report.

Download SprinkCalc on the App Store

MEP Calc — 86+ Engineering Calculators

MEP Calc bundles 86+ engineering modules in one iOS app: 21 fire calculations plus heating, cooling, HVAC, plumbing, steam and natural gas.

Download MEP Calc on the App Store