Sources: TS EN 12845+A2:2026, TS EN 12845-2:2025 and NFPA 13-2025, Standard for the Installation of Sprinkler Systems, 2025 Edition. The US customary units of NFPA are reproduced as printed, and metric equivalents are written only where the standard's own table prints them alongside.
1. Unit system
| Topic | EN 12845 | NFPA 13-2025 |
|---|---|---|
| Base units | Density mm/min, area m², pressure bar, flow L/min, diameter mm (Clause 3, EN p.18) | Density gpm/ft², area ft², pressure psi, flow gpm, diameter in.; metric equivalent in parentheses |
| Which value governs | A single version, metric | Section 1.6.1.3 (PDF p.20): where a value is followed by an equivalent in another unit, the one written first is the requirement |
| Source of conversion | The standard gives no conversion table | Table 1.6.1.2 (PDF p.20): 1 gpm/ft² = 40.746 mm/min; 1 psi = 0.0689 bar; 1 gpm = 3.7848 L/min |
2. Hazard classes
| Topic | EN 12845 | NFPA 13-2025 |
|---|---|---|
| Class list | LH; OH1-OH4; HHP1-HHP4; HHS1-HHS4 (Clause 6.2, EN p.31-32) | Light hazard; Ordinary hazard Group 1-2; Extra hazard Group 1-2; special occupancy hazards (Section 19.2.1.2.4, PDF p.180) |
| Definition of the lowest class | Low fire load and combustibility, single compartment at most 126 m², fire resistance at least 30 min | Occupancies with contents of low quantity and combustibility (Section 4.3.2, PDF p.38) |
| Breakdown of the middle class | Four groups, all at 5.0 mm/min; storage within OH is permitted under three conditions (Clause 6.2.3) | OH1: moderate quantity, low combustibility, stockpile at most 8 ft (2.4 m). OH2: moderate to high quantity and combustibility, stockpile 12 ft (3.7 m), 8 ft (2.4 m) where the rate of heat release is high (Section 4.3.3, PDF p.38) |
| Highest class | HHP1-HHP4 process, HHS1-HHS4 storage | EH1: very high quantity and combustibility, spaces containing dust or lint. EH2: very high quantity, substantial amounts of flammable or combustible liquids, extensive shielding (Section 4.3.4, PDF p.38-39) |
| Where storage sits | A separate class within the standard: HHS, Table 4 and Table 5 | Not a separate class; storage not meeting the conditions of 4.3.1.4-4.3.1.8 goes to Chapters 20-25 (Section 4.3.5, PDF p.39) |
| Area limit per riser | No class based limit | Section 4.4.1 (PDF p.39): light and ordinary hazard 52 000 ft² (4830 m²); extra hazard 40 000 ft² (3720 m²) |
3. Design density and area of operation
EN 12845 Table 3 (Clause 7.1, EN p.36):
| Hazard class | Density (mm/min) | Area, wet or pre-action (m²) | Area, dry or alternate (m²) |
|---|---|---|---|
| LH | 2.25 | 84 | Not allowed, OH1 is used |
| OH1 | 5.0 | 72 | 90 |
| OH2 | 5.0 | 144 | 180 |
| OH3 | 5.0 | 216 | 270 |
| OH4 | 5.0 | 360 | Not allowed, HHP1 is used |
| HHP1 | 7.5 | 260 | 325 |
| HHP2 | 10.0 | 260 | 325 |
| HHP3 | 12.5 | 260 | 325 |
NFPA 13-2025 Table 19.2.3.1.1, Density/Area Criteria (PDF p.181):
| Hazard class | Case where the design area is not required to be 3000 ft² | Case where 3000 ft² (280 m²) is required by Section 19.2.3.1.5 |
|---|---|---|
| Light Hazard | 0.1 gpm per ft² over 1500 ft² (4.1 mm/min, 140 m²) | 0.07 gpm per ft² over 3000 ft² (2.9 mm/min, 280 m²) |
| Ordinary Hazard Group 1 | 0.15 gpm per ft² over 1500 ft² (6.1 mm/min, 140 m²) | 0.12 gpm per ft² over 3000 ft² (4.9 mm/min, 280 m²) |
| Ordinary Hazard Group 2 | 0.2 gpm per ft² over 1500 ft² (8.1 mm/min, 140 m²) | 0.17 gpm per ft² over 3000 ft² (6.9 mm/min, 280 m²) |
| Extra Hazard Group 1 | 0.3 gpm per ft² over 2500 ft² (12.2 mm/min, 230 m²) | 0.28 gpm per ft² over 3000 ft² (11.4 mm/min, 280 m²) |
| Extra Hazard Group 2 | 0.4 gpm per ft² over 2500 ft² (16.3 mm/min, 230 m²) | 0.38 gpm per ft² over 3000 ft² (15.5 mm/min, 280 m²) |
The metric values in parentheses are as printed in the NFPA 13 table. The structural difference is this: EN 12845 gives one pair per class, NFPA 13 splits the same class into two columns. Section 19.2.3.1.4 (PDF p.180) also rules on small areas: below 1500 ft² (140 m²) in light and ordinary hazard the density for 1500 ft² is used, and below 2500 ft² (230 m²) in extra hazard the density for 2500 ft² is used.
The area adjustments diverge as well. For a dry system EN 12845 Table 3 keeps a separate column; 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. NFPA 13 also allows an area reduction for quick response sprinklers (Section 19.2.3.2.3.1 and Figure 19.2.3.2.3.1, PDF p.182; on condition of a wet system, light or ordinary hazard and a ceiling height of at most 20 ft / 6.1 m), and the number of sprinklers in the design area cannot be fewer than five. EN 12845 has no such reduction.
4. Shape of the area of operation
| Topic | EN 12845 | NFPA 13-2025 |
|---|---|---|
| Shape | Rectangular and symmetrical with respect to the sprinkler layout (Clause 13.4.3.1, EN p.99-100) | Rectangular (Section 28.2.4.2.1, PDF p.347) |
| Dimension parallel to the ranges | At least 1.2 times the square root of the area | At least 1.2 times the square root of the area, so as to include the sprinklers on both sides of the cross main |
| If the ranges are not enough | Where the ranges run parallel to the ridge of a roof with a slope greater than 6°, or where there are bays formed by beams deeper than 1.0 m, the coefficient becomes 2 | The design area is extended to adjacent branch lines connected to the same cross main (Section 28.2.4.2.3, PDF p.347) |
5. K-factors
| Topic | EN 12845 | NFPA 13-2025 |
|---|---|---|
| Defined list | Table 37a (EN p.104): LH 57; OH 80 or 115; HHP and HHS ceiling sprinklers 80, 115 or 160 where the density is ≤ 10 mm/min, 115 or 160 where it is > 10 mm/min; HHS intermediate sprinklers 80 or 115 | Table 7.2.2.1 (PDF p.53), metric column: 20, 27, 40, 60, 80, 115, 160, 200, 240, 280, 320, 360, 400, 480 |
| Selection criterion | Hazard class and design density | Product listing; relative discharge is given as a percentage with K-5.6 (80) as the reference |
| ESFR and CMSA | Outside the scope; goes to EN 12845-2 through Annex N and Annex P | Section 7.2.2.5 (PDF p.53): minimum nominal K-factor K-11.2 (160) |
| Flow formula | Q = K√p, Q in L/min, p in bar (Clause 14.3, EN p.104-105) | Section 28.2.4.10.3 (PDF p.349): calculated with the nominal K-factor, with a corrected K-factor used for dry type sprinklers |
| Minimum sprinkler pressure | Clause 13.4.4 (EN p.102): LH 0.70 bar; OH 0.35 bar; HHP and HHS 0.50 bar; K115 in-rack 1.00 bar; K80 in-rack 2.00 bar | Section 28.2.4.11.1 (PDF p.349): the minimum operating pressure of any sprinkler is 7 psi (0.5 bar) |
| Maximum pressure | Clause 8.2.1 (EN p.42): the system pressure shall not exceed 12 bar | Section 28.2.4.12 (PDF p.350): maximum operating pressure 175 psi (12 bar) for extra hazard and Chapter 20-26 sprinklers |
6. Water supply duration and hose stream allowance
| Topic | EN 12845 | NFPA 13-2025 |
|---|---|---|
| Duration | Clause 8.1.1 (EN p.42): LH 30 min, OH 60 min, HHP 90 min, HHS 90 min | Table 19.2.3.1.2 (PDF p.181): light hazard 30 min; ordinary hazard 60 or 90 min; extra hazard 90 or 120 min |
| Condition for the lower duration value | The standard gives a single value | Section 19.2.3.1.3 (PDF p.180): the lower value may be used where waterflow and supervisory devices are electrically supervised and monitored by an approved, constantly attended station |
| Hose stream allowance | No fixed allowance added to the sprinkler demand; Clause 9.2 (EN p.46) requires the town main to meet the manual intervention flow, and NOTE 1 leaves this flow to the authority having jurisdiction | Table 19.2.3.1.2 (PDF p.181): inside hose 0, 50 or 100 gpm (0, 190 or 380 L/min); combined inside and outside light hazard 100 gpm (380 L/min), ordinary hazard 250 gpm (950 L/min), extra hazard 500 gpm (1900 L/min) |
| ESFR, CMSA and storage | TS EN 12845-2:2025 Table 6 (EN p.34): 60 min for 9, 10 and 12 sprinklers; 90 min for 15 and 16; 120 min for 20 to 30 | The duration comes from the tables of Chapters 20-25 (Section 20.15.2 and 20.15.4, PDF p.194) |
7. Sprinkler spacing and coverage area
| Topic | EN 12845 | NFPA 13-2025 |
|---|---|---|
| Maximum area per sprinkler | Table 19 (EN p.70): LH 21.0 m²; OH 12.0 m²; HHP and HHS 9.0 m² | Table 10.2.4.2.1(a)-(d) (PDF p.84-85): light hazard hydraulically calculated 225 ft² (20 m²), pipe schedule 200 ft² (18 m²); ordinary hazard 130 ft² (12 m²); extra hazard 100 ft² (9 m²) at densities of 0.25 gpm/ft² (10.2 mm/min) and above |
| Maximum spacing | Table 19: in a standard layout S and D are 4.6 m in LH; 4.0 m in OH; 3.7 m in HHP and HHS | Light and ordinary hazard 15 ft (4.6 m); extra hazard and high piled storage at high density 12 ft (3.7 m) |
| Absolute upper limit | The rows of Table 19 | Section 10.2.4.2.2 (PDF p.84): 225 ft² (20 m²) shall not be exceeded in any case |
| Minimum spacing | Clause 12.3 (EN p.72): spacing of less than 2 m is not allowed; baffles, in-rack intermediate sprinklers and stairwells are the exceptions | Section 10.2.6.4.1 (PDF p.85): 6 ft (1.8 m); Section 10.2.6.4.2 allows closer placement subject to a baffle |
| Distance to the wall | Clause 12.4.1 (EN p.72): 2.0 m for standard spacing, 2.3 m for staggered spacing | Section 10.2.6.2.1 (PDF p.85): half the distance between sprinklers; Section 10.2.6.3: minimum 4 in. (100 mm) from a wall |
8. Pipe calculation and C values
Both standards use Hazen-Williams for the friction loss. EN 12845 Clause 13.2.1 (EN p.82-83) states that the calculations shall not be less than those derived from the formula and ties the C values to Table 22; NFPA 13 Section 28.2.4.8.1 (PDF p.348) points to the same formula and to Table 28.2.4.8.1.
| Pipe | EN 12845 Table 22 (EN p.83) | NFPA 13-2025 Table 28.2.4.8.1 (PDF p.349) |
|---|---|---|
| Cast iron | 100 (cast iron) | 100 (unlined cast or ductile iron) |
| Ductile iron | 110 | 100 (unlined), 140 (cement-lined cast or ductile iron) |
| Steel, wet system | 120 (mild steel) | 120 (black steel, wet systems including deluge) |
| Steel, dry system | No separate row, again 120 | 100; 120 where nitrogen, vacuum or a vapour phase corrosion inhibitor is applied |
| Galvanized steel | 120 | 120 in a wet system, 100 in a dry system, 120 with nitrogen or vacuum |
| Stainless steel and copper | 140 | 150 (copper tube, brass or stainless steel) |
| Plastic and reinforced glass fibre | 140 (reinforced glass fibre); no separate row for plastic | 150 (plastic all, listed) |
| Cement lined and concrete | 130 (spun cement, cement lined cast iron) | 140 (asbestos cement, concrete) |
The distinction is clear: EN 12845 ties the C value to the type of pipe alone, while NFPA 13 gives two separate values for the same type of pipe depending on the system type and on the gas or inhibitor arrangement in a dry system. To use the equivalent length tables with a different C value, NFPA 13 gives the multipliers of Table 28.2.3.2.1 (PDF p.347): 0.713 for C 100; 1.16 for 130; 1.33 for 140; 1.51 for 150. There is no counterpart on the EN 12845 side; instead Clause 13.2.3 (EN p.83) sets a velocity limit: 6 m/s through any valve, flow monitoring device or strainer, 10 m/s at any other point.
9. Choice of calculation method
| Topic | EN 12845 | NFPA 13-2025 |
|---|---|---|
| Sizing from tables | Pre-calculated systems: LH (Clause 13.3.3, EN p.86), OH (13.3.4, EN p.88), HHP and HHS (13.3.5, EN p.89) | Pipe schedule method (Section 19.2.2, PDF p.180); Table 19.2.2.1 gives 15 psi (1 bar) and 500-750 gpm (1900-2850 L/min) for light hazard, 20 psi (1.4 bar) and 850-1500 gpm (3200-5700 L/min) for ordinary hazard |
| Limit of the table route | Full calculation is mandatory for layouts with intermediate level HHS sprinklers and for gridded or looped layouts (Clause 13.1, EN p.82) | Section 19.2.2.3 (PDF p.180): the pipe schedule may be used for (1) new systems of 5000 ft² (465 m²) or less and (2) new systems exceeding 5000 ft² where the flows of Table 19.2.2.1 are available at a minimum residual pressure of 50 psi (3.4 bar) at the highest sprinkler elevation; Section 19.2.2.2 leaves extra hazard to hydraulic calculation |
| Method options | Pre-calculated or fully calculated | Section 19.2.3.1.1 (PDF p.180): density-area, room design or special design areas |
Field note: the most frequent mistake when comparing two projects is converting the unit system without converting the protection concept. The single density-area pair of EN 12845 and the two column, correction factor construction of NFPA 13 cannot be reduced to the same line; the comparison must be made under the same concept heading, with the clause numbers kept visible.
Frequently Asked Questions
How are the design densities of NFPA 13 and EN 12845 compared?
Short answer: EN 12845 Table 3 (EN p.36) gives a single density-area pair for each class: LH 2.25 mm/min and 84 m², OH1-OH4 5.0 mm/min and 72/144/216/360 m², HHP1-HHP3 7.5/10.0/12.5 mm/min and 260 m². NFPA 13-2025 Table 19.2.3.1.1 (PDF p.181) gives two columns for each class: light hazard 0.1 gpm/ft² over 1500 ft² (4.1 mm/min over 140 m²), ordinary hazard Group 1 0.15 gpm/ft² (6.1 mm/min), Group 2 0.2 gpm/ft² (8.1 mm/min), extra hazard Group 1 0.3 gpm/ft² over 2500 ft² (12.2 mm/min over 230 m²), Group 2 0.4 gpm/ft² (16.3 mm/min).
How is the hose stream allowance handled in the two standards?
NFPA 13-2025 Table 19.2.3.1.2 (PDF p.181) gives the hose stream allowance and the duration together for hydraulically calculated systems: light hazard total 100 gpm (380 L/min) and 30 minutes; ordinary hazard 250 gpm (950 L/min) and 60 or 90 minutes; extra hazard 500 gpm (1900 L/min) and 90 or 120 minutes. For an inside hose connection 0, 50 or 100 gpm (0, 190 or 380 L/min) is added. EN 12845 has no fixed hose stream allowance added to the sprinkler demand; Clause 9.2 (EN p.46) only requires the town main to meet the manual intervention flow, and NOTE 1 states that this flow is normally determined by the authority having jurisdiction.
Do the K-factor lists overlap?
EN 12845 Table 37a (EN p.104) defines four nominal K-factors: 57 for LH, 80 or 115 for OH, 80, 115 or 160 for HHP and HHS ceiling sprinklers, 80 or 115 for HHS intermediate sprinklers. NFPA 13-2025 Table 7.2.2.1 (PDF p.53) gives a list of fourteen rows; the metric equivalents are 20, 27, 40, 60, 80, 115, 160, 200, 240, 280, 320, 360, 400 and 480. Section 7.2.2.5 sets the minimum nominal K-factor for CMSA and ESFR sprinklers at K-11.2 (160).
Are the C values different in the pipe friction calculation?
Both standards use Hazen-Williams, but they choose the C value by a different criterion. EN 12845 Table 22 (EN p.83) looks only at the type of pipe: cast iron 100, ductile iron 110, mild steel 120, galvanized steel 120, cement lined cast iron 130, stainless steel 140, copper 140. NFPA 13-2025 Table 28.2.4.8.1 (PDF p.349) takes the system type into account along with the type of pipe: black steel 120 in wet systems, 100 in dry systems; 120 in dry systems as well where nitrogen, vacuum or a vapour phase corrosion inhibitor is used; plastic 150, copper, brass and stainless steel 150.
How do sprinkler spacings and coverage areas differ?
EN 12845 Table 19 (EN p.70) gives the maximum area per sprinkler for sprinklers other than sidewall as 21.0 m² in LH, 12.0 m² in OH and 9.0 m² in HHP and HHS; in a standard layout the maximum S and D values are 4.6 m, 4.0 m and 3.7 m respectively. NFPA 13-2025 Table 10.2.4.2.1(a) (PDF p.84) gives 225 ft² (20 m²) and 15 ft (4.6 m) for light hazard in hydraulically calculated systems, and Table 10.2.4.2.1(b) gives 130 ft² (12 m²) and 15 ft (4.6 m) for ordinary hazard. Section 10.2.4.2.2 states that 225 ft² (20 m²) shall not be exceeded in any case.
Is the shape of the area of operation calculated the same way in both standards?
The coefficient is the same, the wording differs. EN 12845 Clause 13.4.3.1 (EN p.99-100) requires, in gridded configurations, the length L parallel to the ranges to be greater than or equal to 1.2 times the square root of the area of operation; where the ranges run parallel to the ridge of a roof with a slope greater than 6°, or where bays are formed by beams deeper than 1.0 m, the coefficient becomes 2. NFPA 13-2025 Section 28.2.4.2.1 (PDF p.347) requires, in the density-area method, the design area to be rectangular and its dimension parallel to the branch lines to be at least 1.2 times the square root of the operating area.
References
TS EN 12845+A2:2026 and TS EN 12845-2:2025
- Clause 3 definition of K-factor (EN p.18)
- Clause 6.2, 6.2.3, 6.2.4 (EN p.31-32), Clause 6.3.2 (EN p.33)
- Clause 7.1 and Table 3 (EN p.35-36), Table 4 (EN p.38), Table 5 and Table 6 (EN p.39)
- Clause 8.1.1 and 8.2.1 (EN p.42)
- Clause 9.2 and 9.6 (EN p.46, EN p.55-56)
- Clause 12.2 and Table 19 (EN p.70), Clause 12.3 and 12.4.1 (EN p.72)
- Clause 13.1 and 13.2.1 (EN p.82), Table 22 and Clause 13.2.3 (EN p.83), Clause 13.3.3, 13.3.4, 13.3.5 (EN p.86-89)
- Clause 13.4.3.1 (EN p.99-100), Clause 13.4.4 (EN p.102), Table 37a and Clause 14.3 (EN p.104-105)
- TS EN 12845-2:2025 Clause 4 (EN p.6), Table 6 (EN p.34)
NFPA 13-2025, Standard for the Installation of Sprinkler Systems
- 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, 4.3.4.1 (PDF p.38); Section 4.3.4.2, 4.3.5, 4.4.1 (PDF p.39)
- Table 7.2.2.1 and Section 7.2.2.5 (PDF p.53)
- Table 10.2.4.2.1(a), Table 10.2.4.2.1(b), Section 10.2.4.2.2 (PDF p.84)
- Table 10.2.4.2.1(c), Table 10.2.4.2.1(d), Section 10.2.6.2.1, 10.2.6.3, 10.2.6.4.1, 10.2.6.4.2 (PDF p.85)
- Section 19.2.1.2.4, 19.2.2.2, 19.2.2.3, 19.2.3.1.1, 19.2.3.1.3, 19.2.3.1.4 and Table 19.2.2.1 (PDF p.180)
- Table 19.2.3.1.1 and Table 19.2.3.1.2 (PDF p.181)
- Section 19.2.3.2.3.1, 19.2.3.2.3.2 and Figure 19.2.3.2.3.1 (PDF p.182); Section 19.2.3.2.6 (PDF p.183)
- Section 20.15.2 and 20.15.4 (PDF p.194)
- Section 28.2.4.2.1, 28.2.4.2.3 and Table 28.2.3.2.1 (PDF p.347); Section 28.2.4.8.1 (PDF p.348)
- Table 28.2.4.8.1, Section 28.2.4.10.3, 28.2.4.11.1 (PDF p.349); Section 28.2.4.12 (PDF p.350)
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Download MEP Calc on the App StoreTS EN 12845+A2:2026 (EN 12845:2015+A2:2026) Fixed firefighting systems — Automatic sprinkler systems — Design, installation and maintenance; TS EN 12845-2:2025 (EN 12845-2:2024) ESFR and CMSA sprinkler systems. Every figure in this article is taken from the published standard text; clause, table and page references are listed under References. General information only, not a substitute for the standard or for a design review.