NFPA 13, EN 12845 and FM Global: A Three-Way Comparison

Three standards do the same job: controlling a fire with sprinklers. But they diverge on units, density definition, water supply duration and approval regime. This page puts all three side by side in one table.

Identity cards

Item	NFPA 13	BS EN 12845	FM Global
Publisher	National Fire Protection Association (US)	CEN/TC 191 (Europe)	FM Global (an insurer)
Nature	Code / installation standard	Installation standard	Insurer guidance (Data Sheet)
Units	gpm/ft², psi, ft² (SI in brackets)	mm/min, bar, m² (SI only)	US units with SI in brackets (same document)
Binding force	Where local regulation adopts it	A national standard in CEN member states	Contractual, as a policy condition
Equipment approval	Listed (UL, FM and others)	EN 12259 series plus CE	FM Approved only

Design logic: the largest difference

All three standards tie a single density-area point to the hazard class; the differences lie in the numbers and in how the area changes. NFPA 13-2025 has no density-area curve: Table 19.2.3.1.1 holds the area at 140 m² for light and ordinary hazard and raises the density with the class, and uses 230 m² for extra hazard. The area changes only through defined modifications: a reduction for quick-response sprinklers (19.2.3.2.3), plus 30 percent for dry and double interlock pre-action systems (19.2.3.2.6), and 280 m² where unsprinklered combustible concealed spaces exist (19.2.3.1.5). EN 12845 Table 3 does the opposite: across OH1 to OH4 the density stays at 5.0 mm/min and the area grows from 72 to 360 m². FM Global DS 3-26 gives density and area by hazard category (HC-1/2/3) and ceiling height (Table 2.3.1.10); in the ordinary and high categories its area is larger than NFPA's.

Parameter	NFPA 13	EN 12845	FM Global
Density definition	One point per hazard class (Table 19.2.3.1.1)	Fixed density plus fixed area (Table 3)	Table by hazard category and ceiling height (DS 3-26 Table 2.3.1.10)
Light hazard	4.1 mm/min over 140 m²	2.25 mm/min over 84 m²	HC-1: 4 mm/min over 140 m²
Ordinary hazard	6.1–8.1 mm/min over 140 m²	5.0 mm/min over 72–360 m²	HC-2: 8 mm/min over 230 m² (some occupancies HC-3)
High hazard (process)	12.2–16.3 mm/min over 230 m²	7.5–12.5 mm/min over 260 m²	HC-3: 12 mm/min over 230 m²
Pipe sizes from tables	Pipe schedule, limited (19.2.2)	Pre-calculated tables: LH, OH1–OH4 and HHP/HHS (Tables 6 and 7)	None; hydraulic calculation
K-factor notation	K5.6 (K80), K8.0 (K115), K11.2 (K160), K25.2 (K360)	K80, K115, K160, K360	US notation with SI in brackets: K14.0 (K200)

NFPA values are from Table 19.2.3.1.1 (OH1 6.1, OH2 8.1; EH1 12.2, EH2 16.3 mm/min), EN values from Table 3, and FM values from the wet-system column for ceilings up to 9 m in DS 3-26 Table 2.3.1.10. The hazard classes do not map one to one; the rows show approximate equivalents.

Water supply: this row sets the tank volume

The most expensive difference on site appears in this row. EN 12845 ties the duration directly to the hazard class (8.1.1) and adds no hose allowance to the sprinkler demand; NFPA 13 reaches up to 150 minutes in storage (180 minutes for rubber tyre storage) (Table 20.15.2.6); FM Global asks for 60 minutes plus a hose allowance in every non-storage hazard category (DS 3-26 2.3.1.12–2.3.1.13).

Hazard	NFPA 13	EN 12845	FM Global
Light	30 min plus 380 L/min hose allowance	30 min	60 min plus 950 L/min hose allowance (HC-1)
Ordinary	60–90 min plus 950 L/min hose allowance	60 min	60 min plus 950 L/min hose allowance (HC-2)
High hazard / storage	Extra hazard: 90–120 min plus 1900 L/min; storage: 60–150 min (rubber tyres 180 min)	90 min (HHP and HHS)	HC-3: 60 min plus 1900 L/min; storage: 60–120 min plus 950–1900 L/min (DS 8-9 Table 14)

NFPA durations are from Tables 19.2.3.1.2 and 20.15.2.6; the lower of two values may be used where waterflow alarm and supervisory devices are monitored at a constantly attended location (19.2.3.1.3). EN 12845 durations are from 8.1.1.

Storage and ESFR

NFPA 13 handles storage in its own chapters, with detailed commodity and stacking curves. EN 12845 reads storage from the intersection of Category I to IV with the ST1 to ST6 storage configuration; ESFR and CMSA moved into a separate part, EN 12845-2, in 2024. FM Global covers storage in DS 8-9 and is generally the strictest: it requires a 4-hour fire wall for Group A plastics where NFPA accepts 2 hours.

Maintenance regime

NFPA splits design (13) and maintenance (25) into separate documents. EN 12845 embeds maintenance in its own text: weekly, monthly, quarterly, half-yearly, annual, 3, 10 and 25 year layers all sit within the same standard. FM Global runs maintenance through the insurance survey; a facility without weekly test records loses its premium discount.

Which applies in Turkey?

BYKHY Article 96(5) is explicit: sprinkler system design shall be carried out to TS EN 12845, and Article 96(1) requires system components to comply with TS EN 12259. The regulation makes no direct reference to NFPA; Article 5(2) points designers to Turkish Standards where the regulation is silent, to European Standards where no Turkish Standard exists, and to internationally recognised standards only for matters not covered by Turkish or European Standards. FM Global is not a legal requirement but a contractual condition of the insurance policy. The legal basis for local approval is therefore TS EN 12845; NFPA 13 and FM Global apply as an added layer, provided the regulation's minimum requirements are met. In practice the added layer is decided by three parties: the investor, the insurer and the third-party inspector.

• NFPA 13 (added layer): US-owned facilities, data centres, pharmaceutical plants, FM approved warehouses.
• TS EN 12845 (legal basis): every sprinkler project in Turkey; EU-owned manufacturing, CE-marked export buildings, EU tenders, European-insured logistics.
• FM Global (added layer): every facility in the FM portfolio, and investors targeting a premium reduction.

The critical rule never changes: calculations are never mixed between standards. The TS EN 12845 design is completed in full on its own terms; where an added layer is required, that standard is checked separately and consistently within itself. The standards applied should be written into the contract and visible on the first page of the design file.

Frequently Asked Questions

What is the most fundamental difference between NFPA 13 and EN 12845?

NFPA 13-2025 also gives a single density-area point per hazard class (Table 19.2.3.1.1); the difference is in the numbers. NFPA holds the area at 140 m² for light and ordinary hazard and raises the density; EN 12845 holds the ordinary hazard density at 5.0 mm/min and grows the area from 72 to 360 m². NFPA also adds a hose allowance to the sprinkler demand, EN 12845 does not.

Which standard produces the largest tank?

For non-storage occupancies usually FM Global, because it asks for 60 minutes plus a hose allowance in every hazard category. In storage NFPA 13 can reach 150 minutes (180 minutes for rubber tyres), while FM DS 8-9 asks for at most 120 minutes. EN 12845 fixes 90 minutes at high hazard and adds no hose allowance.

Can I mix two standards on one project?

No. Each standard is internally consistent. Sizing sprinklers to an EN density and the tank to an NFPA duration meets the requirement of neither.

Which is mandatory in Turkey?

Under BYKHY Article 96(5), sprinkler system design is carried out to TS EN 12845; the regulation does not reference NFPA 13. NFPA 13 or FM Global apply as an added layer requested by the insurer or investor, provided the regulation's minimum requirements are met, and should be written into the contract.

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