The scope of the European sprinkler standard, its version structure, and how it differs from NFPA 13 in field practice.
On a logistics warehouse project for an EU-owned client, the insurer set acceptance criteria as "EN 12845 plus LPC Rules", while the mechanical design team had prepared the in-rack sprinkler layout to NFPA 13. The density-area table, the K-factor notation and the water supply duration — none of the three agreed. Converting the project to EN 12845 made one thing plain: the two standards do the same job, but their design philosophy and unit system differ from the outset. This article covers what EN 12845 includes, which version came into force when, and where it diverges from NFPA 13.
What EN 12845 is and what it covers
EN 12845 is the European standard titled Fixed firefighting systems — Automatic sprinkler systems — Design, installation and maintenance. It is prepared by CEN/TC 191, with the secretariat held by BSI. The standard is published in three official languages, and adoption as a national standard is mandatory for CEN members.
Its scope:
- The design, installation and maintenance of fixed sprinkler systems in buildings and industrial plant
- The sprinkler types defined in EN 12259-1, including ESFR and CMSA
- Hazard classification, water supplies, components, testing and commissioning, and extensions to existing systems
Outside the scope: water spray (deluge) systems, sprinkler systems on ships, aircraft and vehicles, underground mining systems, and water supplies for fixed extinguishing systems other than sprinklers.
The definitions clause fixes European terminology. Three terms are unfamiliar to an NFPA reader:
- Area of operation: the maximum area assumed to have sprinklers operating simultaneously (the counterpart of NFPA's design area, but calculated differently)
- Pre-calculated system: a system where pipe sizes, density-area and length limits are taken from tables (similar to an NFPA pipe schedule but more restricted)
- Fully calculated system: a system requiring hydraulic calculation — all high-hazard process and storage designs, and anything exceeding the area of operation limits
Version structure
There is no single "EN 12845" — several versions circulate in practice:
| Version | Date | Scope / what is new |
|---|---|---|
| EN 12845:2015 | 2015 | The main revision, consolidated with the AC:2016 corrigendum |
| BS EN 12845:2015+A1:2019 | December 2019 | Updated by amendment A1, including the UK National Annex. Still the most widely used reference version. |
| EN 12845-2:2024 | 2024 | A new Part 2: a separate part for ESFR and CMSA; storage above 12.2 m and sprinklers above K360 |
| EN 12845:2015+A2:2026 | 2026 | The current main version, superseding A1 and integrating references to the newer parts of the family. Details of the new version → |
📌 2026 update: the European sprinkler standard has become a family of documents. For the detailed changes, see EN 12845:2026 (+A2): the new version.
BS EN 12845:2015+A1:2019 withdraws EN 12845:2015 and its corrigendum. Text changed by amendment A1 is marked in the standard with amendment tags; watch for those when revising a design.
The most important change brought by Part 2 is that the former ESFR annex has been taken out of the main standard and rewritten as a separate part. Part 2 covers separate design curves for CMSA, the in-rack decision for palletised storage, and ESFR compatibility with powered smoke venting. The old CMSA and ESFR annexes are being withdrawn from Part 1; during the transition you will meet projects referencing both.
Hazard classes and design density
EN 12845 gives three main hazard categories with sub-groups. For pre-calculated systems, design density and area of operation are fixed:
| Hazard class | Density (mm/min) | Area of operation (m²) | Typical application |
|---|---|---|---|
| LH (Light Hazard) | 2.25 | 84 | Schools, offices, hospital room areas |
| OH-1 | 5.0 | 72 (wet) / 90 (dry) | Cinemas, hotel bedroom blocks |
| OH-2 | 5.0 | 144 | Restaurants, laundries, dairies |
| OH-3 | 5.0 | 216 | Car parks, textile workshops, printing |
| OH-4 | 5.0 | 360 | Tobacco, leather processing, match manufacture |
| HHP-1 | 7.5 | 260 | Light industrial process |
| HHP-2 | 10.0 | 260 | Paint, varnish, rubber |
| HHP-3 | 12.5 | 260 | Resins, plastics moulding |
| HHP-4 | Foam or deluge — project specific | Flammable liquids, distilling | |
For high hazard storage the table is more complex: commodity category, storage configuration and stack height form a three-dimensional selection matrix.
Side by side with NFPA 13
The two standards solve the same problem, but diverge in several places:
| Topic | EN 12845 | NFPA 13 |
|---|---|---|
| Units | SI only: mm/min, L/min, bar, m² | US customary native: gpm/ft², psi, ft², with SI in brackets |
| Density-area definition | A single density per hazard class plus a fixed area of operation | A density-area curve: density varies with area |
| K-factor notation | K57, K80, K115, K160, K200, K240, K280, K320, K360 (metric) | K2.8, K4.2, K5.6, K8.0, K11.2, K14.0, K16.8, K22.4, K25.2 (US) |
| Design method | Pre-calculated (pipe sizes from tables) or fully calculated | Pipe schedule is limited; hydraulic calculation is the norm |
| Water supply duration | 30 min (LH), 60 min (OH), 90 min (HH) | 30–60 min light and ordinary, 60–120 min extra hazard and storage, risk based |
| Water supply philosophy | Single / superior single / duplicate / combined classification | Single and multiple supply and dedication rules, referencing NFPA 22 |
| Number of hazard categories | 3 main (LH, OH, HH) plus sub-groups | 5 (Light, OH-1, OH-2, EH-1, EH-2) plus storage |
| Life safety emphasis | The term was removed in 2015; additional reliability measures sit in an annex | NFPA 13 / 13R / 13D separation, with life safety in specific rules |
| ESFR / CMSA | EN 12845-2:2024 as a separate part, or the older annexes | Dedicated chapters within NFPA 13 |
| Maintenance regime | Weekly, monthly, quarterly, half-yearly, annual, 3, 10 and 25 year routines within the standard | Managed by NFPA 25 as a separate standard |
A practical difference: for an OH-3 warehouse EN 12845 gives you 5.0 mm/min × 216 m² = 1080 L/min from the start; NFPA 13 for the equivalent hazard gives a curve starting at 300 gpm = 1135 L/min. Close, but not equivalent. K-factor selection differs too: K80 is standard for OH under EN 12845 with a minimum 0.35 bar at the head, while NFPA works with K5.6 (roughly equivalent) at a 7 psi minimum. Errors accumulate in exactly these small differences when converting.
Where EN 12845 is used in Turkey
BYKHY accepts NFPA 13 and EN 12845 as alternatives for sprinkler design; the choice is settled by the owner and insurer. In practice EN 12845 is used:
- In EU-owned production plants: German, Dutch and Italian investors impose EN 12845 as a group standard.
- In CE-marked prefabricated buildings: modular buildings exported to Europe expect EN 12845 certified suppression.
- In EU tenders and development-bank financed projects: the specification references the CEN series.
- In logistics warehouses insured by European insurers: the third-party inspection report is required in EN 12845 plus LPC Rules format.
- In European shopping centre operators' assets: EN 12845 is common in atrium, car park and storage areas.
NFPA 13 dominates in US-investor projects (data centres, pharmaceutical plants), in part of the public sector, and in FM Global approved warehouses. Mixing the two on one project — sizing sprinklers to NFPA and the pump to EN 12845 — produces mismatched water supply durations, an error we see often on site.
Common errors
- Version confusion: where a specification says "EN 12845", pin the year and amendment down in the contract. Do not take a pre-A1 design to approval today.
- Carrying NFPA terms across: density-area curve, Schedule 40 pipe, QR sprinkler 4.9 K — these have no direct counterpart in an EN 12845 calculation.
- The shape of the area of operation: in EN 12845 it is rectangular with its long side parallel to the range pipes; the NFPA 1.2 × dimension rule does not apply.
- Water supply duration: writing 60 minutes for LH out of NFPA habit, when 30 is sufficient, doubles the tank volume and the capital cost.
- K-factor unit errors: K200 is roughly K14.0, but entering the wrong figure in software working in gpm and psi changes every flow result.
Summary
EN 12845 is Europe's constitution for sprinkler design and maintenance. BS EN 12845:2015+A1:2019 is still the field reference; EN 12845-2:2024 has moved ESFR and high-flow sprinklers into a separate part. The fundamental differences from NFPA 13 are the unit system, the definition of the density-area relationship, and the pre-calculated table approach. Which standard applies in Turkey is decided by the investor, the insurer and the inspection body — settling that at the start of the project is far cheaper than turning back halfway.
Frequently asked questions
What is the fundamental difference between EN 12845 and NFPA 13?
EN 12845 ties a density in mm/min to a fixed area of operation — 5.0 mm/min over 216 m² for OH-3, for instance. NFPA 13 works with density-area curves in gpm/ft² and combinations of K-factor and sprinkler count. EN 12845 allows pipe sizing from tables in pre-calculated systems; NFPA 13 largely requires full hydraulic calculation.
What is the difference between Part 1 and Part 2?
Part 1 covers conventional control mode sprinklers and the storage rules. Part 2 defines design criteria for ESFR and high-flow sprinklers above K360, and for storage configurations above 12.2 m, as a separate document.
Is EN 12845 mandatory in Turkey?
BYKHY accepts NFPA 13 and EN 12845 as alternatives. However, CE-marked manufacturing, EU tenders, insurer-driven logistics warehouses and third-party inspections mostly prefer EN 12845, and for prefabricated buildings exported to Europe it is effectively mandatory.
How do the hazard classes map onto NFPA categories?
Roughly: LH to Light Hazard, OH 1–4 to Ordinary Hazard Groups 1–2, HHP to Extra Hazard process, HHS to Storage. Because the density units and the definition of the operating area differ, treating them as equal is misleading — map the hazard group, then redo the calculation.
Which countries does EN 12845 apply in?
It is in force as a national standard in the 34 CEN member countries, including every EU state, the United Kingdom, Switzerland, Norway, Iceland, Turkey, Serbia and North Macedonia. In Turkey it is published as TS EN 12845.
SprinkCalc — Fire Sprinkler Design Across Three Standards
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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 StoreBS EN 12845:2015+A1:2019 Fixed firefighting systems — Automatic sprinkler systems. EN 12845-2:2024 (CMSA & ESFR sprinkler systems). NFPA 13 Standard for the Installation of Sprinkler Systems. Turkish Regulation on Fire Protection of Buildings (BYKHY). FM Global Property Loss Prevention Data Sheet 2-0.