What Is EN 12845? Scope, Classification and Key Differences from NFPA 13

EN 12845 is the core standard governing the design, installation and maintenance of automatic sprinkler systems in Europe. Its current edition in Türkiye is TS EN 12845+A2:2026. This article rests on two sources: the text of TS EN 12845+A2:2026 and the copy of NFPA 13-2025 (Standard for the Installation of Sprinkler Systems, 2025 Edition). Every value on the NFPA side has been read from the image of the relevant page and is given together with its section or table number.

Identification

National Foreword (TS p.3): the standard was prepared by the CEN/TC 191 "Fixed firefighting systems" Technical Committee, approved by CEN on 19.01.2026 and adopted as a Turkish Standard at the 21.05.2026 meeting of the Technical Board of the Turkish Standards Institution. On publication it supersedes TS EN 12845+A1:2020 and is identical to EN 12845:2015+A2:2026. European Foreword (TS p.4): the standard exists in three official versions (English, French, German); a translation made under the responsibility of a CEN member has the same status as the official versions.

Clause 1: scope and exclusions

Clause 1 (TS p.17 / EN p.14) draws the boundaries of the standard:

• It specifies requirements and gives recommendations for the design, installation and maintenance of fixed fire sprinkler systems in buildings and industrial plants; it contains specific requirements for sprinkler systems that are an integral part of measures for the protection of life safety.
• It covers only the sprinkler types specified in EN 12259-1 (see Annex L).
• The requirements also apply to any addition, extension, repair or other modification to a sprinkler system. It does not apply to water spray or deluge systems.
• It covers the classification of hazards, water supplies, components, installation and testing, maintenance and the extension of existing systems; it does not cover water supplies to systems other than sprinklers.
• It is only for buildings and plants on land. It is not valid for systems on ships, aircraft, vehicles and mobile fire appliances, nor for underground systems in the mining industry.
• Deviations may be permitted provided that at least an equivalent level of protection is demonstrated and the design criteria are fully documented.

Introduction (TS p.15 / EN p.12): a sprinkler system consists of one or more water supplies together with one or more sprinkler installations; each installation consists of a set of main control valves and a pipe array fitted with sprinkler heads.

Hazard classes

Clause 6.1 (TS p.33-34 / EN p.30-31): the hazard class shall be determined before design begins. Where there are areas in open communication with different classifications, the higher design criterion is extended into the lower classified area by at least two rows of sprinklers.

• LH (Clause 6.2.2): occupancies with low fire load and low combustibility, with no single compartment greater than 126 m² and with a fire resistance of at least 30 minutes.
• OH (Clause 6.2.3): occupancies where materials of medium fire load and medium combustibility are processed or manufactured; four groups (OH1-OH4).
• HHP (Clause 6.2.4.1): high fire load and high combustibility; four groups (HHP1-HHP4). HHP4 is normally protected by deluge and is outside the scope.
• HHS (Clause 6.2.4.2): storage of goods whose height exceeds the limits of 6.2.3; four categories (HHS1-HHS4).

Design criteria: Table 3

Table 3 (Clause 7.1, TS p.39 / EN p.36):

A sample piece of arithmetic: for OH3, 5.0 mm/min x 216 m² = 1 080 L/min. On the HHS side the criteria are read from Table 4 (ceiling or roof protection only, TS p.41 / EN p.38) and Table 5 (with in-rack sprinklers, TS p.42 / EN p.39).

Water supply and duration

Clause 8.1.1 (TS p.45 / EN p.42): LH 30 min, OH 60 min, HHP 90 min, HHS 90 min. NOTE: in the case of town mains, inexhaustible sources and all pre-calculated systems, the duration is implicit in the other requirements of the standard. Clause 9.1 (TS p.49 / EN p.46) lists the supply types: town mains, storage tanks, inexhaustible sources, pressure tanks. Clause 9.6 grades them by reliability as single, superior single, duplicate and combined supplies. Clause 8.2.1 (TS p.45 / EN p.42): except under test conditions, the water pressure shall not exceed 12 bar.

Pipe sizing and sprinkler selection

Clause 13.1 (TS p.85 / EN p.82): pipe sizes are determined by the pre-calculated or the fully calculated method. Full calculation is always used for layouts with intermediate level HHS sprinklers and for gridded or looped layouts. Clause 13.2.1 (TS p.86 / EN p.83) states that the friction loss shall not be less than that derived from the Hazen-Williams formula and that the C values are taken from Table 22. Clause 13.2.3 limits the velocity: 6 m/s through any valve, flow monitoring device or strainer, 10 m/s at any other point.

Table 37a (TS p.107 / EN p.104) gives the K-factors: 57 for LH, 80 or 115 for OH, 80, 115 or 160 for HHP and HHS ceiling sprinklers depending on the density, 80 or 115 for HHS intermediate sprinklers. The flow formula is in Clause 14.3: Q = K√P, Q in litres per minute, P in bar. Clause 14.4 (TS p.108 / EN p.105): sprinklers are chosen with a temperature rating close to but no lower than 30 °C above the highest anticipated ambient temperature.

Key differences from NFPA 13

The headings below are drawn from the directly comparable provisions of the two texts.

1. Scope. EN 12845 Clause 1 governs design, installation and maintenance together; the maintenance routines are in Clauses 20 and 21. NFPA 13-2025 Section 1.1.1 (PDF p.19) limits itself to "minimum requirements for the design and installation of automatic fire sprinkler systems and exposure protection sprinkler systems". Section 1.3.1 (PDF p.19) lists the field of application as the character and adequacy of water supplies and all materials and accessories including the installation of sprinklers, fittings, piping, valves and private fire service mains. Section 1.1.2 excludes water mist systems and directs them to NFPA 750; Section 1.1.3 states that the standard is written on the assumption that a single fire will occur within a building. Section 1.3.2 requires sprinklers to be installed throughout all areas of a sprinklered building except where the standard specifically permits otherwise.

2. Unit system. EN 12845 is metric throughout. NFPA 13-2025 Section 1.6.1.3 (PDF p.20) sets the rule: where a measured value is followed by an equivalent in another unit, the value written first shall be regarded as the requirement. Since NFPA 13 prints the US customary unit first with the metric equivalent in parentheses, it is the US customary side that governs. Table 1.6.1.2 (PDF p.20) gives the conversion: 1 gpm/ft² = 40.746 mm/min.

3. Hazard classes. The number of classes and the underlying logic differ between the two standards:

4. Density and area of operation. EN 12845 Table 3 gives a single density-area pair for each class. NFPA 13 Table 19.2.3.1.1 (PDF p.181) offers two options for each class: the normal case and the case where the design area is required to be 3000 ft² (280 m²) by Section 19.2.3.1.5. For light hazard the printed values are 0.1 gpm/ft² over 1500 ft² (4.1 mm/min over 140 m²) and 0.07 gpm/ft² over 3000 ft² (2.9 mm/min over 280 m²).

5. Hose stream allowance. EN 12845 has no fixed hose stream allowance added to the sprinkler demand; Clause 9.2 (TS p.49 / EN p.46) only requires the town main to be able to meet the additional flow needed for manual intervention (hydrants, hose reels), and NOTE 1 states that this flow is normally determined by the authority having jurisdiction. NFPA 13 Table 19.2.3.1.2 (PDF p.181) gives the allowance as a number: light hazard 100 gpm (380 L/min), ordinary hazard 250 gpm (950 L/min), extra hazard 500 gpm (1900 L/min), and 0, 50 or 100 gpm (0, 190 or 380 L/min) for inside hose connections.

6. Dry system penalty. EN 12845 Table 3 keeps a separate area column for dry and alternate systems (90 m² instead of 72 for OH1, 325 m² instead of 260 for HHP) and does not allow dry systems in LH and OH4. NFPA 13 Section 19.2.3.2.6 (PDF p.183) increases the operating area by 30 percent without changing the density for dry pipe and double interlock preaction systems.

7. Minimum and maximum pressure. EN 12845 Clause 13.4.4 (TS p.105 / EN p.102) requires 0.70 bar in LH, 0.35 bar in OH and 0.50 bar in HHP and HHS at the most unfavourable sprinkler. NFPA 13 Section 28.2.4.11.1 (PDF p.349) sets the minimum operating pressure for any sprinkler at 7 psi (0.5 bar) regardless of the hazard class. On the maximum side, EN 12845 Clause 8.2.1 limits the system pressure to 12 bar; NFPA 13 Section 28.2.4.12 (PDF p.350) gives the maximum operating pressure as 175 psi (12 bar) for extra hazard and for sprinklers within the scope of Chapters 20-26.

Field note: when comparing the two standards, the similarity of the class names is misleading. The OH of EN and the Ordinary Hazard of NFPA carry the same word, but the classification criteria, densities and areas are defined separately; a conversion can only be made by placing the relevant clause of both texts side by side.

The standard family and what A2:2026 brings

• EN 17451 (pump sets): Clause 10.1 requires water supplies consisting of pumps to comply with EN 17451, and Clause 4.4.4.4 for the documents, Clause 10.9.3 for the site commissioning test and Clause 18.2.5.2 for the installer data to be displayed on the pump all refer to the same standard.
• EN 12845-3 (earthquake): Clause 13.1 recommends applying the requirements of EN 12845-3 in areas at risk of earthquakes.
• Annex N (TS p.165 / EN p.162) CMSA and Annex P (TS p.167 / EN p.164) ESFR: both require EN 12845-2 to be applied together with this document; the class conversion is made with Annex A of EN 12845-2:2024. Annex P also recommends three 50 percent pump sets complying with EN 17451 for the ESFR water supply.
• Annex O (TS p.166 / EN p.163): a sample P&ID. Annex Q (TS p.168 / EN p.165): a recommendation that the periodic inspection be carried out by an independent body.
• EN 12845-2:2024 governs the design and installation of ESFR and CMSA sprinklers; by Clause 4 ESFR is used only in wet installations, and in the tables of Clause 6.6 the nominal K-factors are K200, K240, K320, K360, K400 and K480.

Maintenance and inspection schedule

EN 12845 builds maintenance on a layered schedule: weekly (Clause 20.2.2, pressure and level readings, alarm and pump tests), monthly (20.2.3, battery electrolyte), quarterly (20.3.2), half-yearly (20.3.3), yearly (20.3.4, pump full load flow test), 3-yearly (20.3.5, internal inspection of tanks), 10-yearly (20.3.6, tank cleaning) and the informative 25-year examination (Annex K, TS p.162 / EN p.159). Clause 21 added by A2 (TS p.126 / EN p.123) requires the system to be inspected periodically at least once a year by a competent person.

Frequently Asked Questions

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

Short answer: EN 12845 is metric, gives design density and area of operation as fixed pairs in Table 3, ties the duration to the hazard class and sets no fixed value for a hose stream allowance. NFPA 13-2025, by Section 1.6.1.3, treats the unit written first, the US customary one, as the requirement, gives density and area in two separate columns in Table 19.2.3.1.1, and sets the hose stream allowance and the duration together in Table 19.2.3.1.2. EN 12845 Clause 1 also covers maintenance; NFPA 13 Section 1.1.1 limits itself to design and installation.

What does EN 12845 cover and what does it not cover?

Clause 1 (TS p.17 / EN p.14): the standard specifies requirements and gives recommendations for the design, installation and maintenance of fixed fire sprinkler systems in buildings and industrial plants. It covers only the sprinkler types specified in EN 12259-1. It does not apply to water spray or deluge systems. It is not valid for systems on ships, aircraft, vehicles and mobile fire appliances, nor for underground systems in the mining industry.

How many hazard classes do the two standards define?

EN 12845 Clause 6.2: Light Hazard (LH), Ordinary Hazard (OH1-OH4), High Hazard Process (HHP1-HHP4) and High Hazard Storage (HHS1-HHS4). NFPA 13-2025 Section 19.2.1.2.4 (PDF p.180) lists four headings: light hazard, ordinary hazard (Group 1 and 2), extra hazard (Group 1 and 2) and special occupancy hazards (Chapter 27). Storage is not a separate class in NFPA 13; Section 4.3.5 (PDF p.39) directs storage arrangements that do not meet the conditions of 4.3.1.4 through 4.3.1.8 to Chapters 20 through 25.

How many minutes must the water supply last?

EN 12845 Clause 8.1.1 (TS p.45 / EN p.42): LH 30 minutes, OH 60 minutes, HHP 90 minutes, HHS 90 minutes. NFPA 13-2025 Table 19.2.3.1.2 (PDF p.181) gives the duration together with the hose stream allowance: light hazard 30 minutes, ordinary hazard 60 or 90 minutes, extra hazard 90 or 120 minutes. Section 19.2.3.1.3 (PDF p.180) states that the lower duration value may be used only where waterflow and supervisory devices are electrically supervised and monitored by a constantly attended station.

How does the area of operation increase in a dry system?

EN 12845 Table 3 (TS p.39 / EN p.36) gives a separate column for dry and alternate systems: OH1 90 m² instead of 72 m², OH2 180 m² instead of 144 m², OH3 270 m² instead of 216 m², HHP1-HHP3 325 m² instead of 260 m². Dry systems are not allowed in LH and OH4. NFPA 13-2025 Section 19.2.3.2.6 (PDF p.183) requires the sprinkler operating area to be increased by 30 percent without changing the density for dry pipe and double interlock preaction systems.

What did the A2:2026 amendment bring?

The main additions marked in the text: reference to EN 17451 for pump sets (Clause 10.1, 4.4.4.4, 18.2.5.2), a recommendation for EN 12845-3 in earthquake risk areas (Clause 13.1), application of EN 12845-2 through Annex N for CMSA and Annex P for ESFR, Annex O for a sample P&ID, and Clause 21 together with Annex Q requiring a periodic system inspection at least once a year.

References

TS EN 12845+A2:2026 and TS EN 12845-2:2025 (EN 12845-2:2024)

• National Foreword (TS p.3), European Foreword (TS p.4), Introduction (TS p.15 / EN p.12)
• Clause 1 Scope (TS p.17 / EN p.14)
• Clause 6.1, 6.2.2, 6.2.3 (TS p.33-34 / EN p.30-31), Clause 6.2.4.1, 6.2.4.2 (TS p.35 / EN p.32)
• Clause 7.1 and Table 3 (TS p.38-39 / EN p.35-36), Table 4 (TS p.41 / EN p.38), Table 5 (TS p.42 / EN p.39)
• Clause 8.1.1 and 8.2.1 (TS p.45 / EN p.42)
• Clause 9.1, 9.2 (TS p.49 / EN p.46), Clause 9.6.1-9.6.4 (TS p.58-60 / EN p.55-57)
• Clause 10.1 (TS p.60 / EN p.57), Clause 10.9.3 (TS p.69 / EN p.66)
• Clause 13.1 (TS p.85 / EN p.82), Clause 13.2.1 with Table 22 and Clause 13.2.3 (TS p.86 / EN p.83), Clause 13.4.4 (TS p.105 / EN p.102)
• Table 37a (TS p.107 / EN p.104), Clause 14.3, 14.4 (TS p.108 / EN p.105)
• Clause 18.2.5.2 (TS p.119 / EN p.116), Clause 20.2-20.3 (TS p.122-125 / EN p.119-122), Clause 21 (TS p.126 / EN p.123)
• Annex K (TS p.162 / EN p.159), Annex L (TS p.163 / EN p.160), Annex N (TS p.165 / EN p.162), Annex O (TS p.166 / EN p.163), Annex P (TS p.167 / EN p.164), Annex Q (TS p.168 / EN p.165)
• TS EN 12845-2:2025 (EN 12845-2:2024) Clause 1, Clause 4, Clause 6.6.1 and Table 7

NFPA 13-2025, Standard for the Installation of Sprinkler Systems

• Section 1.1.1, 1.1.2, 1.1.3, 1.3.1, 1.3.2 (PDF p.19)
• Section 1.6.1.3 and Table 1.6.1.2 (PDF p.20)
• Section 4.3.2, 4.3.3.1, 4.3.3.2 (PDF p.38); Section 4.3.4.2, 4.3.5 (PDF p.39)
• Section 19.2.1.2.4, 19.2.3.1.2, 19.2.3.1.3 (PDF p.180)
• Table 19.2.3.1.1 and Table 19.2.3.1.2 (PDF p.181)
• Section 19.2.3.2.6 (PDF p.183)
• Section 28.2.4.11.1 (PDF p.349), Section 28.2.4.12 (PDF p.350)

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