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) | Published in both unit sets |
| 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
NFPA 13 uses a density-area curve: enlarge the area and you may reduce the density, which gives the designer a trade-off. EN 12845 fixes a single point: the hazard class hands you both the density and the area, with no trade. FM Global uses a fixed hazard class table rather than a curve, and generally produces the most conservative result.
| Parameter | NFPA 13 | EN 12845 | FM Global |
|---|---|---|---|
| Density definition | Density-area curve | Fixed density plus fixed area | Hazard class table |
| Light hazard | 4.1 mm/min over 139 m² | 2.25 mm/min over 84 m² | HC-1 |
| Ordinary hazard | 6.1–8.2 mm/min over 139 m² | 5.0 mm/min over 72–360 m² | HC-2 / HC-3 |
| High hazard (process) | 12.2–16.3 mm/min over 232 m² | 7.5–12.5 mm/min over 260 m² | HC-3 |
| Pipe sizes from tables | Pipe schedule, limited | Pre-calculated, including OH-4 | None; hydraulic calculation |
| K-factor notation | K5.6, K8.0, K11.2, K25.2 | K80, K115, K160, K360 | Imperial notation |
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 and leaves no room for argument; NFPA 13 can reach 120 minutes in storage scenarios; FM Global keeps the hose allowance and the safety factor generous.
| Hazard | NFPA 13 | EN 12845 | FM Global |
|---|---|---|---|
| Light | 30 min | 30 min | 30 min plus hose allowance |
| Ordinary | 60–90 min | 60 min | 60 min plus hose allowance |
| High hazard / storage | 60–120 min | 90 min | 60–180 min plus safety factor |
The most common error: sizing the sprinklers to one standard and the tank to another. A project that multiplies an EN density by an NFPA duration may look coherent on paper but meets the requirement of neither standard.
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 accepts NFPA 13 and EN 12845 as alternatives for sprinkler design; FM Global is not a legal requirement but a contractual condition of the insurance policy. In practice the decision is made by three parties: the investor, the insurer and the third-party inspector.
- NFPA 13: US-owned facilities, data centres, pharmaceutical plants, FM approved warehouses.
- EN 12845: EU-owned manufacturing, CE-marked export buildings, EU tenders, European-insured logistics.
- FM Global: every facility in the FM portfolio, and investors targeting a premium reduction.
The critical rule never changes: a project is built on one standard. That choice 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 uses a density-area curve, giving the designer a trade-off between area and density. EN 12845 ties one density and one area of operation to the hazard class, with no trade.
Which standard produces the largest tank?
Usually FM Global, because it keeps the hose allowance and safety factor most generous. EN 12845 fixes 90 minutes at high hazard; NFPA 13 can reach 120 minutes in storage scenarios.
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?
BYKHY accepts both as alternatives. The choice follows the investor, the insurer and the third-party inspector, and should be written into the contract.
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 StoreNFPA 13 Standard for the Installation of Sprinkler Systems (2025). BS EN 12845:2015+A1:2019 and EN 12845-2:2024. FM Global Property Loss Prevention Data Sheets 2-0, 3-26 and 8-9. Turkish Regulation on Fire Protection of Buildings (BYKHY). Values are for information; the full text of the standard governs in design.