ESFR Sprinklers: NFPA 13 and EN 12845 Tables and Limits

An ESFR sprinkler is a fast-response sprinkler designed to suppress a storage fire before it grows, but it only delivers that result inside the narrow limits the standard sets. This page brings together every ESFR design table, layout rule, system type requirement, hydraulic and water supply provision and prohibition in NFPA 13-2025, TS EN 12845+A2 and TS EN 12845-2, each with its clause number.

Sources: NFPA 13-2025, TS EN 12845+A2:2026-05 (EN 12845:2015+A2:2026) and TS EN 12845-2:2025-12 (EN 12845-2:2024). The two standards are covered in separate sections, followed by a side-by-side comparison, a single list of prohibitions, some common assumptions the texts do not support, and a checklist. For NFPA, the SI and US figures are the table's own values; we have not converted anything. Symbols: ⛔ prohibited or outside the limits, ⚠ conditional, ✓ permitted. Where a standard is silent on a point, we say so.

What an ESFR sprinkler is: the two definitions

EN 12845-2 explains that ESFR and CMSA were developed for storage fires, that ESFR is a development derived from CMSA, and that it typically cuts the heat release rate of storage risks considerably. The standard still expects final extinguishment to be carried out by the fire service in every case (Introduction).

Which document says what

NFPA 13-2025 keeps the ESFR rules in one standard but spreads them over several chapters: selection and installation in Chapter 14 (with 9.5 for position and spacing, as modified by 14.2), general storage rules in Chapter 20, the ESFR design tables in Chapter 23, in-rack and special designs in Chapters 25–26, and hydraulic calculation in Chapter 28 (14.1, 14.2.1, 23.1, 23.2.1).

TS EN 12845+A2 mentions ESFR only in normative Annex P: for ESFR systems EN 12845-2 is applied together with this standard (P.1); because the hazard classification systems differ, classes are converted using EN 12845-2 Annex A (P.2); and three 50 % pump sets to EN 17451 are recommended for the ESFR water supply (P.1). A2 itself contains no ESFR design values, tables or prohibitions. Table C.1 in Annex C lists tyres stored horizontally as Category IV, with a remark that they fall under Annex P. For more on the annex, see our EN 12845 Annex P article.

TS EN 12845-2 sets the design and installation requirements for ESFR and CMSA and is used in addition to the EN 12845 series (Clause 1). Its own Table 1 shows which task sits in which document; the normative references cite the EN 12845:2015+A1:2019 edition.

NFPA 13-2025

Scope and permitted uses

• ✓ ESFR sprinklers designed to Chapter 23 can protect light hazard, ordinary hazard and any storage arrangement with an OH1, OH2, EH1 or EH2 design basis (23.1.1).
• ✓ ESFR sprinklers designed to meet the ESFR criteria of Chapter 20 or Chapters 23–26 can also protect light and ordinary hazard occupancies, in which case 10.2.8.2 may be used for obstructions (14.2.6, 14.2.6.1). The annex explains that this is not meant to allow ESFR to be laid out to light/ordinary hazard spacing; it gives flexibility on distance to walls where walls are added to an existing ESFR system to form light or ordinary hazard areas (A.14.2.6).
• ✓ CMSA and ESFR can protect Class I–IV commodities, Group A plastics, miscellaneous storage and other storage covered in Chapters 20–25 or in other NFPA standards (20.2.2). ESFR is also one of the sprinkler types permitted in light hazard occupancies (9.4.3.1).
• Storage protected by ESFR follows Chapter 20 (23.1), and the design criterion is chosen from 23.3–23.6 (23.2.1). Ceiling criteria for single-, double- and multiple-row racks assume an open-rack arrangement (23.1.3).
• ⛔ ESFR cannot protect storage on solid-shelf racks unless the solid shelves have in-rack sprinklers to Chapter 25 (23.1.3.1).
• ⛔ ESFR is not used for storage in open-top containers (23.1.3.2).
• ⛔ The operating pressure may not be lower than the value given in Chapter 23 for the storage type, commodity, storage height and building height (23.1.3.3).

The preface to the 2025 edition records that the ESFR location criteria in Chapter 14 were changed, that the obstruction rules were revised on the basis of an FPRF report, and that K-28 (400) and K-33.6 (480) ESFR sprinklers were added to Chapter 23. Tables 23.3.1, 23.5 and 23.6 in this edition, however, have no column for either K-factor; K-28.0 and K-33.6 appear only in 7.2.2.3 and in the deflector distance clauses (14.2.9.1.1.1–2).

Sprinkler characteristics

System type

As a general storage rule, sprinkler systems are wet pipe; dry and preaction systems are permitted for storage where there is a risk of freezing or other special conditions (20.16.2.1, 20.16.2.2). For ESFR, 14.2.2 applies on top of that.

Roof slope and building height

• ⛔ ESFR sprinklers are installed only in buildings whose roof or ceiling pitch does not exceed 4 in 12 (14.2.3).
• ⚠ The Chapter 20–26 criteria apply up to a 2 in 12 (16.7 %) slope (20.9.1). Where the design has been increased to 18 sprinklers because of slope, the area is five sprinklers on each of the three most demanding branch lines plus three on the next most demanding line (28.2.4.4.1).
• On corrugated metal deck, building height is measured to the underside of the deck where the corrugation is 75 mm (3 in) deep or less, and to the highest point where it is deeper; with insulation, it is measured to the underside of the insulation (20.9.2.1–20.9.2.4).

Protection area and spacing (14.2.7, 14.2.8)

Table 14.2.7.2.1 — Protection areas and maximum spacing of ESFR sprinklers

The m² column of the table shows 9, while the text of 14.2.7.2.2 gives the same 100 ft² as 9.3 m² (a rounding difference within the source).

Annex Figure A.14.2.7.2.3 illustrates the shift rule with bar joists and trusses at 1.7 m (5 ft 6 in) and 1.8 m (5 ft 10 in) centres, measured to the near edge of the member.

Deflector distance below the ceiling (14.2.9)

Obstructed construction, 50 % or less open (14.2.9.1.2.1–14.2.9.1.2.3)

Where the slope exceeds 1 in 12 and the construction is more than 50 % open, the unobstructed rules apply (14.2.9.1.2.4). Deflector orientation follows 9.5.4.3 (14.2.9.2).

Clearance to storage

• ⛔ The clearance between deflector and top of storage is 900 mm (36 in) or more (14.2.11); Chapter 20 also requires at least 900 mm (36 in) for ESFR and CMSA (20.9.6.5).
• The general Chapter 20 rule is 450 mm (18 in); a larger listed clearance applies where the listing requires it, a smaller one may be justified by large-scale fire testing, and rubber tyre storage needs at least 900 mm (36 in) (20.9.6.1–20.9.6.4). The ESFR-specific clause is 20.9.6.5.

Obstructions (14.2.10)

• In addition to 9.5.5, ESFR sprinklers are positioned to 14.2.10 so as to minimise obstruction of the discharge pattern, or supplemental sprinklers are added to cover the hazard (14.2.10.1.1).
• ⚠ Where high-piled storage is not physically separated from an adjacent light or ordinary hazard area, 14.2.10 applies to every ceiling sprinkler within 4.6 m (15 ft) horizontally of the high-piled storage (14.2.10.1.3); the annex gives rack structures and solid piles as examples.
• Ceiling obstructions (beams, ducts, light fittings, truss top chords) follow Table 14.2.10.2.1(a) or (b) and Figure 14.2.10.2.1 (14.2.10.2.1). They do not apply where sprinklers sit either side of an obstruction narrower than 600 mm (24 in), no further from its centreline than half the allowable spacing, or where supplemental sprinklers are installed beneath it (14.2.10.2.2).
• An upright sprinkler relates to its supply pipe in one of three ways: directly on a pipe of 100 mm (4 in) nominal or smaller; offset at least 150 mm (6 in) horizontally from the pipe; or on a sprig raising the deflector at least 300 mm (12 in) above the centreline of a pipe larger than 100 mm (4 in) (14.2.10.2.3).
• Obstructions below the deflector follow 14.2.10.3 (14.2.10.3.1). A pipe, conduit or similar item counts as isolated when it is at least 3 times the width of its nearest neighbour away from it (14.2.10.3.2). Obstructions entirely below the ceiling sprinklers that prevent water reaching the hazard need supplemental sprinklers beneath them (14.2.10.3.3).
• ✓ No supplemental sprinklers are needed (14.2.10.3.4) where the obstruction complies with Table 14.2.10.2.1(a)/(b); is no wider than 38 mm (1½ in) and at least 300 mm (12 in) below the deflector; no wider than 150 mm (6 in) and at least 150 mm (6 in) away horizontally; no wider than 600 mm (24 in) and at least 300 mm (12 in) away horizontally; no wider than 100 mm (4 in), wholly below the pipe feeding the ceiling sprinklers, with an upright sprinkler; or where the occupancy is protected under 14.2.6 and the obstructions comply with 9.5.5.3.
• Supplemental sprinkler spacing (14.2.10.3.5.1): under non-flat or non-solid obstructions, no more than 0.6 m (2 ft) from the edges, linear spacing ≤ 1.2 m (4 ft), area ≤ 1.5 m² (16 ft²); under flat, solid obstructions up to 0.6 m (2 ft) wide, and under a horizontal barrier of the same footprint, linear spacing ≤ 2.4 m (8 ft); under flat, solid obstructions wider than 0.6 m and up to 3.0 m (10 ft), and their barriers, ≤ 3.0 m (10 ft); wider than 3.0 m (10 ft), the unobstructed spacing rules. These sprinklers do not need water shields (14.2.10.3.5.2).
• Quick-response spray sprinklers may be used under sectional and overhead doors (14.2.10.3.6).
• Conveyors (14.2.10.3.7): with no high-piled storage beneath, QR standard spray; with high-piled storage beneath, ceiling-level sprinklers under the conveyor; no supplemental sprinklers where a belt-type conveyor's horizontal profile is at least 70 % open, where a belt conveyor up to 1.2 m (4 ft) wide has no high-piled storage beneath, where a roller conveyor's gap between rollers is at least the roller width, or where a roller conveyor has no high-piled storage beneath.
• For vertical obstructions such as columns, the annex recommends keeping sprinklers at least 300 mm (12 in) from obstructions up to 300 mm (12 in) wide, 600 mm (24 in) from those 300–600 mm (12–24 in) wide, and adding a sprinkler on the far side of columns wider than 600 mm (24 in) (A.14.2.10). The obstruction rules for CMSA and ESFR are essentially the same, apart from the "Three Times Rule" (A.13.2.7.2.1).

Tables 14.2.10.2.1(a) and (b) — Positioning ESFR sprinklers to avoid obstructions to discharge (A: horizontal distance from sprinkler to side of obstruction; B: allowable height of deflector above bottom of obstruction; Figure 14.2.10.2.1)

Draft curtains, roof vents and HVLS fans

• ⛔ Draft curtains are not used within ESFR systems (20.9.5.3).
• ✓ They are permitted at system boundaries, to separate ESFR from control-mode sprinklers, or between hazards (20.9.5.3.1).
• ⚠ Where ESFR adjoins a standard-response sprinkler system, the two areas are separated by a noncombustible draft curtain at least 600 mm (2 ft) deep, with a clear aisle at least 1.2 m (4 ft) wide centred beneath it (14.2.4.1–14.2.4.2, 23.1.2.1–23.1.2.2, 20.9.5.3.2–20.9.5.3.3).
• Automatic roof vents are not required in sprinklered areas (20.9.5.1). ⛔ Where they are fitted, their temperature rating and RTI are higher than the sprinklers' (20.9.5.2).
• Background: the protection criteria assume no roof vents and no draft curtains, both of which can harm performance; manually operated vents should not be opened until the fire is controlled or suppressed (A.20.9.5.1, A.20.9.5.3). In tests with eave windows or louvres open, 87.5 % and 91 % more sprinklers operated (C.6).
• ⚠ HVLS fans in sprinklered buildings, ESFR included: diameter no more than 7.3 m (24 ft); roughly centred between four adjacent sprinklers; at least 900 mm (36 in) vertically between fan and deflector; interlocked to shut down immediately on waterflow alarm; to NFPA 72 where a fire alarm system exists (19.1.7.1, 20.8.1, 20.8.2). The annex reports that in the 2011 FPRF tests (CMDA and ESFR), stopping the fan 90 s after the first sprinkler operated gave successful results.

Design tables (Chapter 23)

Unless stated otherwise, the design area is the 12 most hydraulically demanding sprinklers: four on each of three branch lines (23.2.2). Table 23.3.1 has no column for the number of sprinklers, so this rule applies; hose allowance and duration come from Table 20.15.2.6.

Table 23.3.1 — ESFR ceiling-only options for solid pile, palletised and single-, double- and multiple-row rack storage · minimum operating pressure bar (psi) · P = pendent, U = upright

ᵃ For protecting a lower hazard commodity with a higher hazard criterion, see 20.3.2. ᵇ These options rely on the test criteria of a higher hazard and have not been tested separately. ᶜ Applies to rack storage where all of 23.4 (vertical barriers included) is applied. ᵈ Applies to palletised and solid-piled storage in a closed array. * The footnote mark on this cell is illegible in the source; the value itself is legible. — means no option for that K and orientation. The source table also has a row in the exposed expanded Group A group that is "—" throughout; we left it out because it carries no information.

23.4 — Exposed expanded Group A plastics in single-, double- and multiple-row racks

According to the annex, these criteria come from tests under 12.2 m (40 ft) and 9.1 m (30 ft) ceilings with K-25.2 intermediate ESFR and vertical barriers fixed to the uprights at about 4.9 m (16 ft) centres; in the test where the transverse flues were not blocked, the number of operating sprinklers dropped from 11 to 7 (A.23.4).

Table 23.5 — ESFR protection of rubber tyres · wet systems only

ᵃ Shape of the design area to 23.2.2. ᵇ In this application the ESFR is expected to control the fire rather than suppress it. ᶜ Design area of the 20 most demanding sprinklers, five on each of four branch lines, with a minimum operating area of 150 m² (1600 ft²).

Table 23.6 — ESFR protection of roll paper storage · maximum storage height permitted · NA: not applicable

Related general rules (20.7.1–20.7.5): wet systems in tissue areas; heavyweight and mediumweight paper stored horizontally counts as a closed array; the wrapping conditions refer to 18 kg (40 lb).

Table 20.17.1.2(c) — ESFR protection for indoor storage of idle wood pallets

⛔ Wood pallets are not stored in racks unless protected to Table 20.17.1.2(a) or (c) (20.17.1.3).

Table 20.17.2.2.3 — ESFR pendent protection for idle plastic pallets on the floor or in open-frame racks · bar (psi)

* Chapter 25, for exposed unexpanded Group A plastics. ⛔ Plastic pallets are stored in racks only when protected to Table 20.17.2.2.3 (20.17.2.3).

ESFR with in-rack sprinklers (Chapter 25)

• CMDA, CMSA and ESFR ceiling criteria are also an option for open racks fitted with in-rack sprinklers to the solid-shelf criteria (25.3.2).
• ⚠ Where ESFR at ceiling level protects solid-shelf racks, in-rack sprinklers go beneath every tier below the highest solid shelf (25.3.3.4).
• In-rack sprinklers in open racks combined with an ESFR ceiling: quick-response, ordinary temperature, at least K-8.0 (K-115) (25.6.1.2), at a maximum horizontal spacing of 1.5 m (5 ft) (25.6.2.2).
• Notes to Figure 25.6.2.1: in-rack sprinklers OT, QR, pendent or upright, K-8.0 (K-115); at least eight in-rack sprinklers at 227 L/min (60 gpm) (Table 25.6.2.3 gives the same flow as 230 L/min); maximum storage 12.2 m (40 ft) in the figure, with the in-rack level at the tier nearest 50 % of the storage height. The ft and m figures on the multiple-row spacing label in the figure do not agree with each other, so we have not used that label.
• The ESFR ceiling design with in-rack sprinklers follows Table 25.6.3.1; pressure may not be below the tabulated value and the design area follows 23.2 (25.6.3.1–25.6.3.3).

Table 25.6.2.3 — In-rack design with an ESFR ceiling · number of in-rack sprinklers @ L/min (gpm)

Table 25.6.3.1 — ESFR ceiling-level design criteria for rack storage supplemented with in-rack sprinklers

In-rack protection independent of the ceiling (25.7). Closed-top (no open-top containers) Class I–IV and Group A in single-, double- and multiple-row racks may be protected independently of the ceiling (25.7.1.1). The ESFR options are Option 2a, at least K-14.0 (K-200), and Option 2b, at least K-22.4 (K-320), both standard coverage, pendent, fast-response, ordinary temperature ESFR (Table 25.7.2.2; Options 1 and 3 are CMDA). ⛔ In-rack systems are wet pipe only (25.7.2.1). In-rack sprinklers are at least 700 mm (27 in) apart and within the rack footprint; in a single-row rack against a full-height wall 0.3 m (1 ft) away or less, Option 2a/2b in-rack sprinklers may go in that gap (25.7.2.3.2–25.7.2.3.3). Water demand is the Table 20.15.2.6 hose allowance plus the in-rack demand, with duration from Table 20.15.2.6, and the supply must be able to meet the in-rack design independently of the ceiling (25.7.3.3.1–25.7.3.3.3).

* May increase to 2.6 m (8.5 ft) where transverse flues are 1.3 m (4.25 ft) apart or less.

Table 25.7.3.1 — In-rack design, ESFR rows · number of in-rack sprinklers @ minimum L/min (gpm)

* Where exposed expanded Group A is protected, five sprinklers on the most remote rack and five on the nearest adjacent rack.

Special designs (Chapter 26) and column protection

Hydraulics and water supply

• Design area: the 12 most demanding sprinklers, 4 on each of 3 branch lines (23.2.2); with the ESFR method, the design area follows the relevant parts of Chapters 23 and 25 (28.2.4.4).
• ⚠ Tyre rows with 20 sprinklers: 5 on each of 4 branch lines, at least 150 m² (1600 ft²) (Table 23.5 ᶜ). Close spacing with baffles: at least 71 m² (768 ft²) (23.2.3). 18 sprinklers because of slope: five on each of three lines plus three on the next (28.2.4.4.1).
• Minimum water demand = hose allowance (Table 20.15.2.6) + sprinkler demand (20.15.2.6). Ceiling-independent in-rack systems take their own hose allowance and duration from the same table (25.7.3.3).
• Supplemental sprinklers may be designed for the hazard beneath the obstruction, treating the underside of the obstruction as the ceiling (20.16.4); the related Chapter 28 calculation clause ties the discharge pressure of CMSA and ESFR supplemental sprinklers to 20.16.4 and does not require that supplemental level to be balanced with the ceiling system. Supplemental sprinklers added to the design area for obstructions are not counted in the "number of sprinklers" column of Table 20.15.2.6 for CMSA and ESFR.

Table 20.15.2.6 — Hose stream allowance and water supply duration, ESFR rows

ᵃ For CMSA and ESFR, sprinklers added for obstructions are not counted in this column. ᶜ For on-tread, on-side and laced tyres in open portable steel or palletised portable racks, pile ≤ 7.6 m (25 ft), building ≤ 9.1 m (30 ft), with K-14.0 (K-200) or K-16.8 (K-240) ESFR, the duration is 180 minutes. The table also has a row for alternative protection to 25.7 at 950 L/min (250 gpm), 60 min.

Existing systems, drawings, inspection

• When modifying an existing ESFR system that protects a light or ordinary hazard occupancy, the area may follow Table 10.2.4.2.1(a) (light hazard only), spacing 10.2.5 and obstructions 10.2.7.2 (30.6.5–30.6.5.3).
• Annex material: the spare sprinkler cabinet list should identify the sprinkler (upright, pendent, residential, ESFR and so on) (A.16.2.7.7.1); showing structural details on drawings matters where they affect performance, as with ESFR (A.28.1.3(4)); on tolerance to random variations in flue width and alignment, the annex refers to large-scale Test 7, in which eight K-14 (K-200) ESFR sprinklers operated (Annex C).
• NFPA 13 contains no acceptance, inspection or test clause specific to ESFR.

TS EN 12845+A2 and TS EN 12845-2

Scope and hazard classes

• EN 12845-2 sets out design and installation requirements for automatic systems with ESFR and CMSA sprinklers, to this standard and in addition the EN 12845 series; it does not cover every legal requirement, and national regulations may apply in some countries (1). Annex A is used to determine FH and HHS (4).
• ⛔ ESFR and CMSA are not applied to FH3–FH5 occupancies (6.2).
• ✓ Where used in FH1 and FH2 (including storage permitted by EN 12845:2015+A1:2019 Table 2), they are designed as HHS1–HHS3 under 6.6/6.7 regardless of the storage category, and every ESFR/CMSA installation requirement applies (6.2).
• ⛔ Goods not covered by the design tables (such as flammable liquids, aerosols and single pallet loads of them) are not protected to this document; EN 12845 applies where applicable (6.1).
• ✓ Every design in Table 11 can also protect HHS4 up to 20 m² and up to 1.8 m storage height, or an FH (non-storage) risk excluding ignitable liquids (note before Table 11).

Table A.1 — Conversion of EN 12845:2015 classes to EN 12845-2 (read together with 6.2)

Storage goods containing plastics are classified with the flow chart in Figure A.1. The end points that read clearly are: "special commodity" as HHS5; expanded plastics not sealed in cartons (UEP/EEP) HHS5; cartoned expanded plastics (CEP) HHS4; exposed unexpanded plastics (UUP/ENP) HHS4; cartoned unexpanded plastics (CUP/CNP) HHS3; non-combustible products on wooden pallets or in metal containers HHS1; the remaining branches lead to HHS2/HHS3. The thresholds at the intermediate nodes and the exact path of every arrow need to be read from the figure itself, so we have not quoted the percentages here.

Definitions. An open-top container is a box that is open at the top and can hold water: a five-sided container holds water and delays its descent through the flues; one with fewer than five full-height sides directs water unevenly; a five-sided open container of combustible material speeds up horizontal fire spread; a non-combustible open container speeds it up where combustible containers sit beneath (3.1.1). ⛔ Open-top containers are not used in ESFR-protected storage unless a clause expressly allows it; a non-combustible open container counts as closed only if everything beneath it is non-combustible or it is on the bottom tier (4). Roll paper arrays (3.1.2–3.1.5):

Sprinkler characteristics

System type

General design rules (6.1, 6.3, 6.4)

• ⛔ The design is based on the Clause 6 tables; interpolation and extrapolation are not permitted (6.1).
• ✓ The criterion for a K-factor at a given ceiling height may be used for a lower ceiling, provided the other parameters stay the same. Protection for a higher category covers a lower one, and unless stated otherwise HHS3 protection is used for HHS1 and HHS2 (6.1).
• ⚠ Where more than one single pallet load of a higher category sits within any 300 m², the design follows that category (6.1).
• ⛔ All flues ≥ 150 mm; in STC3 and STC4.3 no more than 6 m between loading aisles; loading aisles ≥ 1.2 m unless the design table asks for more (6.1).
• The storage area limits of EN 12845:2015+A1:2019 Table 2 do not apply; consulting the authorities on a limited area, to support final manual extinguishment, is recommended (6.1).
• ⛔ Conveyors and automated handling systems are arranged to stop when the first sprinkler operates (6.1).
• ⛔ Unless stated otherwise, at least 1 m clearance from deflector to top of goods; clearances above 4 m need no correction of the design parameters, because the tables are based on the maximum ceiling height (6.1).
• ⚠ Adjacent areas with different protection concepts: a draft curtain at the ceiling is mandatory where RTIs differ at the same ceiling height, or where ESFR is installed at a higher ceiling than adjacent CMSA or standard sprinklers; the curtain is ≥ 600 mm deep, between the two sprinkler types and noncombustible, positioned to 5.1.3.8; a completely clear aisle ≥ 1.2 m wide separates the two areas, its centreline on the midpoint between the two sprinkler types (6.3).
• ⛔ Water supply duration and design area shape follow Table 6; where a branch line has fewer sprinklers than assumed, all of them are taken as operating and the number of branch lines is increased. No favourable design area is needed, and pipe sizes may not be reduced to limit the favourable area demand (6.4).

Table 6 — Water supply duration and shape of design area

For the 10-sprinkler row, the shape given in the table and the wording of 6.6.1.2 do not match; 6.6.1.2 describes the 10-sprinkler design as three sprinklers on each of three adjacent branch lines plus one on an additional line. The table's in-rack note points to the relevant clauses, and its other two notes are CMSA-specific.

Ceiling-only protection: Tables 7, 8 and 9 (6.6.1.1)

Table 7 holds the ESFR ceiling-only criteria; it is based on ceiling height and generally assumes 12 sprinklers operating. ✓ When Table 7 is used, 5.2.6.1 (horizontal air movement) and 5.3.3.2.2 (obstructions above racks) do not apply. Table 8 covers rubber tyres and Table 9 free-standing roll paper stored on end.

Table 7 — Minimum operating pressure for at least 12 ESFR sprinklers, ceiling-only design for HHS · bar · P = pendent, U = upright

ᵃ Only where all the exposed expanded plastics requirements (vertical barriers included) are applied. ᵇ Palletised and solid-piled storage in a closed array. ᶜ (K400 and K480 columns) no multiple-row racks. ᵈ (K400 column) ceiling to deflector no more than 325 mm. ᵉ Minimum aisle 1.8 m. ᶠ Minimum aisle 2.4 m. "-" means no option for that K and orientation. In the HHS4 rows, K320 (5.2 bar) and K360 (4.1 bar) are higher than K200 and K240; that is exactly how the source reads.

Exposed expanded plastics (with Table 7) and HHS5 12-sprinkler design (5.4)

The source words the ceiling distance differently in the two places: 325 mm to the element in the Table 7 note, 350 mm to the deflector in 5.4.

Table 8 — Minimum operating pressure for a 12 ESFR sprinkler design for rubber tyres · bar

ᵃ The STC3 limits do not apply to tyres; instead, portable racks without an open base or laced storage have either 100 mm flues around them or, where 4 pallets are grouped in one direction, 600 mm aisles and 300 mm flues.

Table 9 — Minimum operating pressure for ESFR designs for rolled paper storage · bar

ᵃ 16-sprinkler design. ᵇ 25-sprinkler design. Although the table heading says 12 sprinklers, the lightweight paper rows use 16 and 25. Wrapping rule (6.6.1.1): lightweight paper fully wrapped on the sides and both ends, or wrapped on the sides with steel bands (one layer of 18 kg basis weight heavy paper, or two layers below 18 kg), may be treated as mediumweight, and mediumweight under the same conditions as heavyweight. Heavyweight or mediumweight paper stored horizontally is protected as a closed array.

Designs with special requirements: Tables 10 and 11 (6.6.1.2)

Tables 10 and 11 are designs with special requirements; where they are used, all of the following apply:

• ⛔ 5.2.6.1 (horizontal air movement) always applies; where there are obstructions above the racks, the recommended approach of 5.3.3.2.2 (in-rack supplementary sprinklers to 5.3.3.2.3) is followed.
• ⛔ Minimum design area (number of sprinklers × area per sprinkler) 71 m², except where obstructed construction requires a sprinkler in every channel. If it falls below 71 m² and sprinklers are not needed in every channel, the number of sprinklers in the ceiling design is increased.
• A 9-sprinkler design is three on each of three adjacent branch lines; a 10-sprinkler design is three on each of three adjacent lines plus one on an additional line.
• ⛔ The ceiling is of non-combustible material and preferably unobstructed (Figure 23); any beams are less than 70 % open in vertical section.
• ⛔ Where the ceiling counts as obstructed: a) area no more than 9.3 m², and the 10.2 m² allowance of 5.1.3.4 does not apply; b) with slope < 10° and solid member depth > 600 mm, a sprinkler in every channel, staggered horizontally between channels where trusses have openings, the vertical position set in each channel to the standard spacing for an unobstructed ceiling; c) with slope < 5° and depth ≤ 450 mm, normal horizontal spacing and adjusted vertical spacing, and above 450 mm small compartments formed with fire-stopping material; d) with slope < 10° and depth ≤ 300 mm, normal horizontal and adjusted vertical spacing, and above 300 mm small compartments with fire-stopping material; where c) or d) is used, e) horizontal spacing as for an unobstructed ceiling, and f) for slopes up to 10° a vertical distance ≤ 600 mm, or, where the depth exceeds that, the thermal element in a plane no more than 150 mm below the bottom of the solid members (Figure 24).

Table 10 — ESFR design with special requirements up to 12.2 m ceiling height · number of sprinklers @ bar (the table has no orientation column)

Table 11 — ESFR design with special requirements up to 16.8 m ceiling height · number of sprinklers @ bar

ᵃ 10 sprinklers @ 2.8 bar may be reduced to 9 sprinklers @ 2.8 bar where the supply can deliver at least 5.5 bar at the 4 most remote sprinklers (2 on each of 2 lines). ⚠ Note before the table: STC4.3 (multiple-row racks) can be protected only where pallets are smaller than 2 m² with 150 mm flues on every side.

Ceiling plus in-rack: 6.6.2.1

6.6.2.1.1 — Open-frame racks (STC4.1–STC4.3) up to HHS4, ceilings ≤ 13.7 m, pendent ceiling ESFR K200 and above. The supply meets the in-rack and ceiling systems simultaneously, the in-rack demand is added to the ceiling demand and the duration is at least 60 min. Goods up to HHS4 in single- and double-row racks can be protected with K200+ pendent ceiling sprinklers and a single level of in-rack sprinklers in the longitudinal flue only, provided that:

• a) the ceiling ESFR is pendent, at standard spacing, K ≥ 200; b) the racks meet the open-frame definition; c) ⛔ the in-rack sprinklers are wet only;
• d) horizontal layout: single rows to Figures 26/27/28; double rows up to HHS3 to Figure 29 (distance from 1 m up to 3 m; face sprinklers at uprights only); double rows HHS3–HHS4 to Figure 30; multiple rows up to HHS3 to Figure 31; multiple rows with adjacent pallets up to HHS4 to Figure 25;
• e) vertically, at the tier level between ½ and ⅔ of the total storage height;
• f) in-rack hydraulics: at least 230 l/min from the 8 most remote in-rack sprinklers; up to HHS3, 68 °C quick response, K ≥ 115; up to HHS4, K ≥ 160 (the latter preferred);
• g) ceiling design to Table 12.

Table 12 — Ceiling design for HHS4 and below in open-frame racks, ceilings ≤ 13.7 m, pendent ESFR K200 and above · number of sprinklers @ minimum bar

6.6.2.1.2 — Buildings with ceilings above 13.7 m, single- and double-row racks, longitudinal in-rack sprinklers with horizontal barriers, up to HHS4. In-rack sprinklers in the longitudinal flue only; ⛔ no solid shelves in the racks; goods overhang the edge of the horizontal barrier by ≤ 75 mm; flues ≥ 75 mm between pallets; transverse flues ≥ 150 mm at least every 3.0 m; double-row rack depth (aisle to aisle) ≤ 2.7 m; longitudinal in-rack sprinklers ≤ 1.5 m apart horizontally and ≤ 3.5 m vertically; horizontal barriers above the lowest in-rack level and at every other level (1st, 3rd…); in-rack sprinklers 68 °C quick response spray, K ≥ 115; ⛔ storage above the top in-rack level ≤ 3.0 m; in-rack hydraulics: 8 sprinklers where one level is needed, 14 for two or more levels (7 on each of the two most remote levels), each ≥ 115 l/min; ceiling design from Table 7 for HHS4 at an equivalent 7.6 m ceiling; the ceiling and in-rack demands are balanced at the connection point, and the in-rack system has its own feed pipe.

Modular ESFR in-rack, independent of the ceiling: 6.6.2.2

• ✓ An alternative to the standard in-rack designs, using ESFR in a modular in-rack layout; unlimited storage height; HHS1–HHS5; ⛔ open-frame racks only; the supply meets the in-rack demand separately from the ceiling (no summing); duration at least 60 min (6.6.2.2.1). ⛔ Wet only (6.6.2.2.2).
• 68–74 °C pendent ESFR; K and flow from Table 14; face sprinklers no more than 450 mm inside the rack; pipework protected against mechanical damage and discharge not obstructed by rack beams (6.6.2.2.3).
• Horizontal spacing between in-rack sprinklers at least 0.7 m and no more than 1.4 m (apart from the exceptions in the figures); face sprinklers ≤ 450 mm from the rack face or from the outer edge of a pallet overhanging the aisle; all within the rack footprint; where a wall is ≤ 300 mm from the rack, they may sit outside the footprint to cover that flue (Figure 28) (6.6.2.2.4).
• Vertical distance between in-rack levels no more than 9.1 m (HHS4 cartoned expanded plastics and HHS5 uncartoned plastics) or 12.2 m up to HHS3; ≥ 150 mm from top of storage to in-rack deflector; deflector below or just below the horizontal rack member at full load (6.6.2.2.5).
• Whatever the number of levels, there is one design, based on the hydraulically most remote level; number from Table 13, flow from Table 14 (6.6.2.2.6). In an existing sprinklered building using the modular design, where the ceiling system is not adapted to 6.6.2.2.7 and there is no storage above the last in-rack level, the last ESFR in-rack level is calculated for 3 × 4 most remote ESFR operating together (in double rows, 4 on each side of the face = 8 face plus 4 in the longitudinal flue); in single rows 10 sprinklers to Figure 27 (5 on each side). This applies only above racks with the modular design, not to areas such as loading and unloading zones.
• Where the ceiling system follows Table 7 and the in-rack follows 6.6.2.2.6, the ceiling may be designed from Table 7 taking the vertical distance between the top in-rack level and the actual ceiling as the "ceiling height"; the top in-rack level may be treated as the floor; the EN 12845 maximum storage height above the top in-rack level does not apply to this arrangement (6.6.2.2.7).

Table 13 — Number of sprinklers in the modular ESFR in-rack design

ᵃ The calculation includes these 10 sprinklers: the 6 most remote in the most remote rack plus the 4 most remote in the adjacent rack.

Table 14 — Minimum flow in the modular in-rack design

ᵃ Goods cartoned, no exposed surfaces.

Layout: spacing, area, distance below the ceiling (5.1.3)

The vertical distance is measured perpendicular to the floor, between the sprinkler's thermal element and the highest part of the ceiling; on corrugated metal deck up to 75 mm deep it is taken from the underside of the flange, otherwise from the top of the flange (5.1.3.5.1). ⛔ In unobstructed or obstructed construction the deflector is at least 100 mm below the ceiling; the maximum follows Table 2 unless Clause 6 says otherwise (5.1.3.5.2). The clause text says "deflector", while the heading of Table 2 says "thermal element".

Table 2 — Maximum allowable vertical distance of the sprinkler thermal element below the ceiling (mm)

Different values in Clause 6: Table 7 ᵈ 325 mm for K400; 325 mm to the element for exposed expanded plastics; 350 mm to the deflector for HHS5 in 5.4; the 325/425 mm column in Table 11; ≤ 600 mm and 150 mm below the element for obstructed ceilings in 6.6.1.2 f).

• Unobstructed ceiling (5.1.3.5.3): a flat ceiling such as a suspended ceiling; all solid members ≤ 100 mm deep; all solid members ≥ 4.3 m apart; members deeper than 100 mm at least 3.7 m apart with ceilings ≤ 9.0 m, or at least 3.0 m apart with ceilings above 9.0 m. Every other case is obstructed. A solid structural member is one less than 70 % open in vertical section.
• ⛔ In obstructed construction ESFR goes into every channel the construction forms; the exception is where solid members project no more than 300 mm below the ceiling and the sprinklers are below the members. The minimum and maximum spacings of 5.1.3.2 apply within each channel; the minimum spacing between branch lines does not apply to sprinklers in adjacent channels (5.1.3.5.4, Figure 2).
• ⚠ The deflector is preferably parallel to the floor; with a slope of ≤ 10° it may be parallel to the ceiling instead (5.1.3.6).
• ⛔ Clearance: at least 1 m between the ceiling sprinkler deflectors and the top of storage (5.1.3.7, 6.1). Where the obstruction width W ≤ 300 mm, ≥ 450 mm from the bottom of the obstruction to the top of storage; 300 < W ≤ 600 mm, ≥ 900 mm; W > 600 mm, supplementary sprinklers (Figure 11 Note 2).

Building: ceiling slope, ceiling strength, roof lights (5.2.1–5.2.3)

Smoke and heat venting, air movement, mezzanines (5.1.3.8, 5.2.4–5.2.7)

• ⛔ ESFR or CMSA installations use manually operated smoke and heat vents only; drop-out heat vents are not installed (5.2.4).
• ⚠ Where national regulations require automatic vents, sprinkler performance must not be impaired, and one of the following is required: (1) sprinklers directly below the vent opening at ≤ 1.2 m linear spacing, ≤ 0.6 m from the vent edge; if placed inside the roof light, the 5.1.3.5.2 minimum and maximum distances do not apply between the closed roof light and the deflector; at least the same K and orientation as the adjacent ceiling sprinklers, fed by pipe no smaller than the branch line; they need not be added to the hydraulic calculation (Figure 5); (2) standard-response vents with thermal release at ≥ 141 °C; (3) automatic smoke vents triggered individually (5.2.4).
• Sprinklers directly below natural venting openings in the ceiling at ≤ 1.2 m spacing, ≤ 0.6 m from the edge; if placed inside the opening, the 5.1.3.5.2 distances apply between deflector and top of the opening; same K and orientation; they need not be included in the hydraulic calculation (5.2.5, Figure 6).
• ⛔ Horizontal air movement (5.2.6.1): air velocity at the ceiling sprinklers ≤ 1.5 m/s, or automatic shutdown on early fire detection. Where that cannot be met, flame detectors at the ceiling (3.0 m radius around the affected sprinklers) or linear heat detectors at the top of the racks (in every transverse flue within 3.0 m of the affected sprinklers; a temperature rating as low as the ambient allows is recommended), either of which shuts the air movement down automatically. ⛔ No storage directly beneath the openings; distance from goods to the opening perimeter L = ½S + d (S sprinkler spacing, d duct diameter, m). A horizontal baffle ceiling goes under the openings, with sprinklers beneath it at normal spacing; its size W = Q / (283 min/m × h) where the flow is known, or W = 2.6 A* / h where it is not (Q in m³/min, A* opening area in m², h distance from ceiling to top of baffle in m); ceiling sprinklers at least 0.7 × the sprinkler spacing from the baffle perimeter. ⛔ Extract fans and fire dampers close before the first sprinkler operates, with aspirating smoke detection, or fire detection of equivalent performance, in every duct extracting from the protected area. Where the flow is unknown, measuring duct velocity with a pitot tube and micromanometer is recommended; for a circular duct Q = (49/60) × A × V (A in m², V in m/min).
• ⛔ Vertical air movement (5.2.6.2): air velocity between the top of storage and the plane of the ceiling sprinklers ≤ 1.5 m/s. Options: automatic shutdown of the airflow on sprinkler waterflow alarm; flame detection at the ceiling over a 3.0 m radius with automatic shutdown; a 30 % increase in the design area of a wet system; a flat, continuous false ceiling over the affected area with ceiling sprinklers beneath it on the same branch lines and spacing; line-type detection at the rack top in the transverse flues within 3.0 m, with automatic shutdown; ceiling-type sprinklers installed in-rack at the flue intersections where the velocity is 1.5 m/s.
• ⚠ Draft curtains should preferably not be placed within sprinkler arrays; where needed, the sprinklers either side are generally equidistant from the curtain and the obstruction rules are met; draft curtains have been shown to harm sprinkler effectiveness (5.1.3.8, Note 2). The curtain between different protection concepts is mandatory under 6.3.
• ⚠ Mezzanines (5.2.7): quick response or ESFR sprinklers beneath solid mezzanines of combustible construction and/or with a combustible occupancy below; standard-response sprinklers may be used where a sprinkler line runs ≤ 0.6 m from the mezzanine edge and all storage beneath is within that perimeter line, or where there is a draft curtain around the mezzanine. The mezzanine level design depends on the mezzanine height and the occupancy beneath.

Obstructions (5.3)

• The obstruction requirements for ceiling protection, and the compensating measures, are the same for ESFR and CMSA (5.3.1).
• ⛔ In addition to the obstructed/unobstructed ceiling limits, pendent and upright sprinklers are placed at standard spacing to Figures 9 and 11 and Table 3; Table 3 may be interpolated as in Figures 9–10; no object within 300 mm of a sprinkler horizontally, unless it is at least 50 mm above the horizontal plane of the deflector (5.3.2). Figure 11 Note 1: H ≤ 50 % of the maximum linear spacing.

Table 3 — Minimum horizontal distance of ceiling objects to avoid obstructing the umbrella pattern

An object wholly within the hatched area of Figures 9–11 is not an obstruction; one that projects below it is, except a structural member at least 70 % open. Otherwise the obstructed sprinkler is moved to comply with Figures 9–11, or sprinklers are placed either side of the obstruction, equidistant from it and at least 300 mm horizontally from its edge. Grouped obstructions (5.3.3.1): two or more objects closer together horizontally than 3 times the width of the smallest (but never less than 150 mm) count as one, whose width is the smallest dimensions of the two objects plus the gap between them (Figure 12: D + X + W); at 3 times the smallest dimension or at least 150 mm apart they are isolated.

Table 4 — Installation guidelines to avoid obstructing the inner core distribution pattern

An upright sprinkler tolerates isolated objects ≤ 100 mm wide directly beneath it at any vertical distance; an object ≤ 600 mm in its largest dimension is at least 300 mm horizontally from the nearest sprinkler. Figure 13 zones: Zone I no objects; Zone II ≤ 38 mm; Zone III ≤ 150 mm; Zone IV ≤ 300 mm (object ≥ 450 mm above storage) or ≤ 600 mm (≥ 900 mm). Where no supplementary sprinklers are needed, the position of the obstruction relative to the rack flues is checked against Table 5 (5.3.3.2.2).

Table 5 — Obstructions located directly above racks (A = width of obstruction over the flue, B = vertical distance from obstruction to top of storage)

• For an obstruction that does not satisfy 5.3.3.2.2 (5.3.3.2.3), sprinklers may go directly beneath it, but the recommended approach is supplementary in-rack sprinklers at every flue intersection (face and longitudinal) at the top of the rack (Figure 15). These are not added to the ceiling hydraulic design.
• Objects wider than 0.6 m (5.3.3.2.4): isolated flat, solid objects take supplementary sprinklers beneath (Figure 16; same type as the ceiling, same branch line size, same spacing); grouped flat, solid objects follow Figure 17 (both objects wider than 0.3 m) or Figure 18 (at least one ≤ 0.3 m), on condition that H < 3 × A and A + B > 0.6 m; isolated non-flat or non-solid objects follow Figure 19 / Figure 20 (Option 2: no more than 1.2 m linear and 1.5 m² area spacing); grouped ones Figure 21 / Figure 22 (same 1.2 m / 1.5 m²).
• ⛔ Open gratings (5.3.3.3): sprinklers go beneath open gratings such as walkways and open-grid ceilings, unless all of these are met: open plan area ≥ 70 % including light fittings; smallest dimension of the grating openings ≥ 25 mm or the grating depth, whichever is greater; grating at least 0.9 m below the ceiling sprinkler deflectors; no material can fall onto it and form an obstruction; only one open grating between ceiling and floor; the ceiling system protects the occupancy as if the grating were not there. An open grating walkway may not be within the rack structure. Supplementary sprinklers under gratings are not added to the ceiling hydraulics.

Water supply, pumps, inspection

• Duration from Table 6: 60/90/120 min, depending on the number of sprinklers; at least 60 min for ceiling plus in-rack, with the in-rack demand added to the ceiling (6.6.2.1.1); at least 60 min for modular in-rack, met separately from the ceiling (6.6.2.2.1).
• ⛔ No favourable design area is needed; pipe sizes are not reduced (6.4).
• EN 12845-2 has no hose stream provision.
• ✓ EN 12845+A2 Annex P.1 recommends three 50 % pump sets (EN 17451). For pumps, water tanks and supply types, EN 12845-2 Table 1 points to EN 12845 Clauses 8–10.
• EN 12845-2 has no inspection or test clause specific to ESFR; for commissioning, spare sprinklers and maintenance, Table 1 points to EN 12845 Clauses 19, 20.1.4 and 20.

The two standards side by side

Prohibitions and limitations: one list

The lists below are every prohibition and limitation in our source extract: 29 items in NFPA 13-2025 and 34 in EN 12845-2. EN 12845+A2 contains no ESFR prohibitions; A2 only makes EN 12845-2 mandatory and gives a pump recommendation.

NFPA 13-2025 (29)

On top of these, the condition lists for special designs (26.3.7, 26.4.1.3, 26.8.3) and the pallet rack prohibitions (20.17.1.3, 20.17.2.3) appear in the sections above; they are not counted.

EN 12845-2:2024 (34)

Common assumptions the texts do not support

• "12 sprinklers for 60 minutes is always enough for ESFR." In EN 12845-2 Table 6 the duration goes 60/90/120 min with the number of sprinklers; NFPA Table 20.15.2.6 runs from 60 to 150 min, and 180 min in the tyre special case.
• "ESFR never needs in-rack sprinklers." Both standards have cases where in-rack sprinklers are mandatory or an option (NFPA Table 23.3.1, 25.3.3.4, 25.6; EN 12845-2 6.6.2).
• "The slope limit is the same in both." NFPA 4 in 12, EN 12845-2 10° (17.6 %).
• "The clearance is 900 mm in both." NFPA 900 mm (36 in), EN 12845-2 1 m.
• "Maximum spacing is always 3.7 m." In NFPA it is 3.0 m once the ceiling exceeds 9.1 m (30 ft) or storage exceeds 7.6 m (25 ft); in EN 12845-2 it is 3.1 m once the ceiling exceeds 9.1 m.
• "The minimum area is 6 m²." 6 m² in EN 12845-2, 5.9 m² (64 ft²) in NFPA.

Searched for in these texts and not found. In NFPA 13-2025: K-28.0 (400) and K-33.6 (480) design rows in Tables 23.3.1, 23.5 and 23.6; a high temperature rating for ESFR; a dry system design table; sidewall or extended coverage ESFR; a clause setting an absolute building or ceiling height limit (the tables stop at 13.7 m (45 ft) and 20.9.2.6 defers to the listing); an ESFR-specific acceptance, inspection or test clause; a mezzanine provision specific to ESFR; an air velocity (m/s) limit; a clause in those words banning ESFR and standard sprinklers mixed in the same area (there are only the curtain-and-aisle rule at boundaries and the ban on curtains within the system). In EN 12845-2: hose stream allowance; dry or preaction ESFR (expressly prohibited); a high temperature (141 °C) rating for ESFR (141 °C appears only for CMSA dry systems and vent releases); upright K320/K360/K400/K480 designs; sidewall ESFR; a ceiling-only table for ceilings above 16.8 m (storage height is unlimited in the modular in-rack design); a clause specifically allowing open-top containers; an RTI figure; ESFR-specific inspection or testing. In EN 12845+A2: ESFR design values, tables and prohibitions.

Design checklist

1. Fix the standard and edition. On the EN side, apply EN 12845-2 together with EN 12845+A2 as Annex P requires.
2. Classify the hazard. In EN, Table A.1 and Figure A.1; ⛔ no ESFR for FH3–FH5 (OH4, HHP1–3); goods outside the tables (flammable liquids, aerosols) are not protected.
3. Check the storage arrangement: ⛔ no open-top containers; in NFPA ⛔ no solid-shelf racks (except with Chapter 25 in-rack); in EN flues ≥ 150 mm and aisles ≥ 1.2 m.
4. Is the system wet? In NFPA, dry/preaction only with a special listing; in EN there is no dry option. Check the antifreeze/glycol conditions.
5. Ceiling slope: NFPA ≤ 4 in 12 (Chapters 20–26 ≤ 2 in 12); EN ≤ 10°.
6. Measure building, ceiling and storage heights (NFPA 20.9.2; EN 5.1.3.5.1). Find the table row: NFPA Tables 23.3.1/23.5/23.6/20.17; EN Tables 7–14. ⛔ No interpolation or extrapolation in EN.
7. K, orientation and temperature from the tabulated option; NFPA ordinary/intermediate; intermediate K-25.2 (K360) pendent for exposed expanded Group A / HHS5.
8. Apply each table footnote (NFPA ᵇ ᶜ ᵈ; EN ᵃ–ᶠ: multiple-row racks, 325 mm, 1.8/2.4 m aisles).
9. Spacing, area and distance to walls: NFPA Table 14.2.7.2.1 and 14.2.8; EN 5.1.3.2. The every-channel rule for obstructed ceilings.
10. Deflector/element distance below the ceiling: NFPA 14.2.9; EN Table 2 and the different Clause 6 values.
11. Clearance: NFPA ≥ 900 mm (36 in); EN ≥ 1 m.
12. Obstructions: NFPA Tables 14.2.10.2.1(a)/(b) and 14.2.10.3; EN Tables 3, 4, 5 and the open grating conditions.
13. Draft curtains, roof vents, smoke and heat vents, HVLS fans and air movement (EN ≤ 1.5 m/s).
14. Hydraulics: number and shape of design sprinklers (NFPA 23.2.2, 28.2.4.4; EN Table 6), minimum pressure, NFPA hose allowance and duration (Table 20.15.2.6), EN duration (Table 6); in EN no favourable area and no pipe size reduction.
15. Where in-rack is needed: NFPA Chapter 25; EN 6.6.2.1 / 6.6.2.2 and Tables 12–14.
16. In EN, consider the Annex P.1 recommendation of three 50 % pump sets.

Frequently Asked Questions

Can ESFR sprinklers be used on a dry pipe system?

Under NFPA 13-2025 ESFR sprinklers are used on wet pipe systems only; a dry or preaction system is possible only where the ESFR is specifically listed for it (14.2.2). EN 12845-2 has no such exception: ESFR is used in wet installations only, this ESFR concept has no dry option, and an installation using dry pendent ESFR counts as wet (4, 6.5).

How much clearance is needed between an ESFR deflector and the top of storage?

At least 900 mm (36 in) under NFPA 13-2025 (14.2.11, 20.9.6.5) and at least 1 m under EN 12845-2 (5.1.3.7, 6.1). EN 12845-2 adds that a clearance greater than 4 m does not call for any correction of the design parameters.

Can I interpolate between two rows of EN 12845-2 Table 7?

No. Clause 6.1 prohibits interpolation and extrapolation. The same clause lets the criterion for a K-factor at a given ceiling height be used for a lower ceiling, provided all other parameters stay the same, so a ceiling between two tabulated heights can use the higher-ceiling row, but no value is calculated in between.

Which EN 12845 hazard classes rule out ESFR?

EN 12845-2 6.2 states that ESFR and CMSA do not apply to FH3–FH5 occupancies. Table A.1 maps these to OH4, HHP1, HHP2 and HHP3. Where ESFR is used for LH and OH1–OH3 (FH1–FH2), it is designed as HHS1–HHS3 regardless of the storage category.

Are draft curtains allowed under an ESFR ceiling?

NFPA 13-2025 does not allow draft curtains within ESFR systems (20.9.5.3); they are permitted at system boundaries and between hazards, and next to a standard-response system the curtain is noncombustible, at least 600 mm (2 ft) deep, with a 1.2 m (4 ft) clear aisle beneath. EN 12845-2 recommends keeping curtains out of sprinkler arrays (5.1.3.8) but requires a noncombustible curtain at least 600 mm deep and a 1.2 m clear aisle between different protection concepts (6.3).

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