In high hazard storage, intermediate level in-rack sprinklers are covered in two separate clauses of EN 12845: the layout geometry in Clause 12.5 and the hydraulic assumptions in Clause 7.2.3. An in-rack design cannot be verified without reading these two clauses together. Source: TS EN 12845+A2:2026, Clause 12.5, EN p.78-81 and Clause 7.2.3, EN p.37.
When intermediate levels are required
There are two separate triggers.
1. Excessive clearance: Clause 7.2.2.3 (EN p.36-37)
The values in Table 4 are used to determine the clearance. Where the clearance, that is the distance between the storage height and the ceiling sprinkler deflector, exceeds 4 m, one of the following options is applied:
- Option 1: the density is increased by 2.5 mm/min for the first metre of excess. For each subsequent metre the water density is increased by 1 mm/min. A minimum K factor of K115 is used.
- Option 2: intermediate level in-rack sprinklers are provided in accordance with 7.2.3.
In other words, a clearance of 4 m does not by itself make in-rack sprinklers mandatory; increasing the density is an equivalent route.
2. Exceeding the storage height limit: Clause 7.2.2.2 (EN p.36)
Table 4 gives the maximum storage height that can be protected by roof or ceiling protection alone, by category and storage type. Where the storage heights exceed this limit, intermediate level in-rack sprinklers are provided in accordance with 7.2.3.
3. The trigger from the layout rule: Clause 12.5.2 (EN p.78)
An intermediate level is installed above the top level of the storage; the exception is where all roof or ceiling sprinklers are less than 4 m above the storage.
Footnote c) to Table 2 (EN p.34) repeats the same threshold: the relevant protection method is limited to risks where the ceiling sprinklers are less than 4 m above the highest level of the goods stored; where the ceiling sprinklers are more than 4 m above, intermediate level in-rack sprinklers are used.
Clause 12.5.1: general layout and flue distances
- Sprinklers protecting double row racks are installed in the longitudinal flue spaces, preferably at the intersection with the transverse flue (see Figures 13 and 14).
- Where any shelf or structural steelwork could significantly obstruct the water discharge from the sprinklers, additional sprinklers are provided and taken into account in the flow calculation.
- It is ensured that water from sprinklers operating at intermediate levels can penetrate into the goods stored.
- The distance between goods placed back to back in a rack (the longitudinal flue space) shall be at least 0.15 m; pallet stops are fitted where necessary.
- The distance between goods placed side by side in a rack (the transverse flue space) shall be at least 0.1 m.
- The clearance between the sprinkler deflectors and the top of the storage shall be not less than 0.10 m for flat spray sprinklers and not less than 0.15 m for other sprinklers.
Source: EN p.78.
Clause 12.5.2: vertical spacing
The vertical distance from the floor to the lowest intermediate level and between levels does not exceed 3.50 m or two tiers, whichever is the smaller (see Figures 13 and 14). In no case may the highest row of intermediate level sprinklers be installed lower than one tier below the top of the storage (EN p.78).
Clause 12.5.3: horizontal position
| Goods category | Layout | Maximum horizontal distance | Product of horizontal × vertical distance | Page |
|---|---|---|---|---|
| Category I or II | As far as possible within the longitudinal flue, at the intersection with every second transverse flue, staggered relative to the row above (see Figure 13) | 3.75 m | Shall not exceed 9.8 m² | EN p.78 |
| Category III or IV | Within the longitudinal flue, at the intersection with every transverse flue (see Figure 14) | 1.9 m | Shall not exceed 4.9 m² | EN p.80 |
This product condition means that the horizontal and vertical spacings cannot be chosen independently of each other. For example, if a horizontal spacing of 3.75 m is chosen for Category I goods, the vertical spacing is limited to 9.8 / 3.75 = 2.61 m; if a vertical spacing of 3.50 m is wanted, the horizontal spacing falls to 9.8 / 3.50 = 2.80 m. These two figures are the arithmetic that follows from the product of the two limits in the table.
Clause 12.3 (EN p.72) states that sprinklers shall not be installed at spacings closer than 2 m, but lists intermediate level sprinklers in racks among the exceptions to that rule (see 12.5.3).
Clause 12.5.4: number of rows per level
The number of sprinkler rows per level is determined by the total rack width. Where racks are placed back to back, the total width is calculated by adding the width of each rack and the distance between them. One row of sprinklers per level is installed for every 3.2 m of rack width. These are installed in the flue spaces wherever possible (EN p.80).
Clause 12.5.5: HHS intermediate level sprinklers in racks without shelves
For pallet rack storage and multiple row drive-through storage (see Figure 3 and type ST4 in Table 4), intermediate level sprinklers are installed as follows (EN p.80-81):
- a) single row racks not wider than 3.2 m are protected by a single row of sprinklers fitted at the tier levels shown in Figures 13 and 14;
- b) double row racks not wider than 3.2 m are protected by sprinklers located centrally in the longitudinal flue space, at the ends of the stacks and at the tier levels shown in Figures 13 and 14;
- c) double or multiple row racks wider than 3.2 m but not wider than 6.4 m are protected by two rows of sprinklers installed at not more than 3.2 m apart. Each row is at the same distance from the nearest rack edge. The sprinklers at a given level in each line are placed in the same group of transverse flues.
Where any shelf or structural steelwork could significantly obstruct the water distribution of a sprinkler, an additional sprinkler is provided to ensure water distribution in the area that would be obstructed.
Clause 12.5.6: solid or slatted shelf racks (ST5 and ST6)
Where intermediate level sprinklers are required, they are installed above each shelf. Where the roof or ceiling sprinklers are more than 4 m above the goods, or where water access to the goods is restricted, the top shelf is also included. The positioning is as shown in Table 21 and Figure 15. The vertical distance between rows does not exceed 3.5 m. Single rows of sprinklers are located centrally above the shelves; double rows are positioned so that each row is at the same distance from the nearest shelf edge (EN p.81).
Table 21: Position of intermediate level sprinklers in ST5 and ST6 storage (EN p.82)
| Shelf width s (m) | Rows of sprinklers | Maximum distance between sprinklers along the rows (m) | Maximum distance between rows of sprinklers (m) |
|---|---|---|---|
| ST5: s ≤ 1.0 | 1 | 2.8 | - |
| ST6: 1.0 < s ≤ 3.0 | 1 | 2.8 | - |
| ST6: 3.0 < s ≤ 6.0 | 2 | 2.8 | 2.8 |
The distance from the end of the shelf parallel to the range pipe lines to the nearest sprinkler is half the sprinkler spacing along the range lines or 1.4 m, whichever is the smaller (EN p.82).
Clause 7.2.3: hydraulic assumptions
| Subclause | Provision | Page |
|---|---|---|
| 7.2.3.1 | Where more than 50 intermediate level sprinklers are installed in racks, they shall not be fed from the same control valve set as the roof or ceiling sprinklers | EN p.37 |
| 7.2.3.2 | The design density for the roof or ceiling sprinklers shall be at least 7.5 mm/min over an area of operation of 260 m². Where goods are stored above the highest intermediate protection level, the design criteria for the roof or ceiling sprinklers are taken from Table 5 | EN p.37 |
| 7.2.3.3 | For the purpose of hydraulic calculation, 3 sprinklers are assumed to operate simultaneously at each in-rack sprinkler level in the hydraulically most remote position, up to a maximum of three levels. Where the rack aisles are 2.4 m or wider, only one rack is assumed to be involved; where narrower than 2.4 m but equal to or wider than 1.2 m, two racks; where narrower than 1.2 m, three racks. Note: it is not necessary to assume that more than three rows of sprinklers operate simultaneously in the vertical plane and more than three in the horizontal plane | EN p.37 |
| 7.2.3.4 | In-rack sprinklers and the associated ceiling sprinklers are always fully calculated (see 13.1). Note: the minimum pressure at any operating sprinkler is 2.0 bar (see 13.4.4) | EN p.37 |
Clause 13.1 (EN p.82) repeats the same rule: full calculation is always used for arrangements with intermediate level HHS sprinklers and for gridded or looped arrangements.
Pressure: Clause 13.4.4 and the note to 7.2.3.4
Clause 13.4.4 (EN p.102) determines the pressure at the hydraulically most unfavourable sprinkler, with all sprinklers in the area of operation operating, as not less than that required to give the density specified in 13.4.1 or than the following values, whichever is the higher:
| Case | Minimum pressure |
|---|---|
| LH | 0.70 bar |
| OH | 0.35 bar |
| HHP and HHS (excluding in-rack sprinklers) | 0.50 bar |
| K115 in-rack sprinklers | 1.00 bar |
| K80 in-rack sprinklers | 2.00 bar |
The note to Clause 7.2.3.4 states that "the minimum pressure at any operating sprinkler is 2.0 bar" and refers to 13.4.4. The difference between that note and the list in 13.4.4 arises from the K80 in-rack row being 2.00 bar. In design both should be read; the higher value is binding.
Sprinkler type, sensitivity and water shield
- Table 37a (Clause 14.2.1, EN p.104): for HHS intermediate level sprinklers in high piled storage, the permitted types are conventional, spray and flat spray, and the permitted nominal K factors are 80 or 115. For HHP and HHS ceiling or roof sprinklers, K 80, 115 or 160 where the design density is up to 10 mm/min, and K 115 or 160 above 10 mm/min. A K factor above K160 is not covered by EN 12845-1.
- Table 38 (Clause 14.5.1, EN p.106): only "Quick" sensitivity is permitted for in-rack sprinklers; Standard 'A' and Special sensitivity are not permitted. All three sensitivities are permitted for the ceiling sprinklers above in-rack sprinklers. Clause 14.5.1 also requires that, where sprinklers are located in racks, the sprinklers at the ceiling have a sensitivity equal to or slower than that of the sprinklers in the racks.
- Clause 14.7 (EN p.106): sprinklers installed in racks or below perforated shelves, platforms, floors and the like, where water from one or more sprinklers higher up could wet the area near the bulb or fusible element, are provided with a metal water shield at least 0.075 m in diameter. Water shields on upright sprinklers are not connected directly to the deflector or to the yoke, and any bracket supports are designed to minimize obstruction to the sprinkler water distribution. The standard does not exempt the top level from this rule.
- Clause 14.2.2 (EN p.104): sprinklers without a fixed deflector shall not be used in or under racks.
- Clause 12.1.2 (EN p.70): in HHP and HHS a clear space of at least 1.0 m is maintained below the deflector of the roof and ceiling sprinklers.
The relationship with goods category and ESFR
The classification of stored goods into Categories I-IV is given in Annex B (methodology, EN p.127-131) and in Annex C (product list). Annex A is the list of hazard class (LH, OH, HHP) occupancies; Annex D is "Zoning of sprinkler installations".
Annex P (normative, EN p.164) gives the direction for ESFR systems: EN 12845-2 applies in conjunction with this document for ESFR sprinkler systems, and Annex A of EN 12845-2:2024 applies because of the different hazard classification systems. EN 12845-2:2024 contains only Annex A; it has no other annex. Arrangements in which ESFR ceiling sprinklers are used together with in-rack sprinklers are addressed in Clause 6.6.2 of that standard.
Frequently Asked Questions
Are intermediate level sprinklers mandatory where the ceiling sprinklers are more than 4 m above the storage?
Not mandatory; one of two options is applied. TS EN 12845+A2:2026 Clause 7.2.2.3 (EN p.36-37): where the clearance between the storage height and the ceiling sprinkler deflector exceeds 4 m, either Option 1 is applied, that is the density is increased by 2.5 mm/min for the first metre of excess and by a further 1 mm/min for each subsequent metre, with a minimum of K115; or Option 2 is applied, that is intermediate level in-rack sprinklers are provided in accordance with 7.2.3. As a separate provision, Clause 12.5.2 requires an intermediate level to be installed above the top level of the storage unless all ceiling or roof sprinklers are less than 4 m above the storage.
What vertical distance is permitted between intermediate levels?
Clause 12.5.2 (EN p.78): the vertical distance from the floor to the lowest intermediate level and between levels does not exceed 3.50 m or two tiers, whichever is the smaller. In no case may the highest row of intermediate level sprinklers be installed lower than one tier below the top of the storage.
What is the minimum pressure at in-rack sprinklers?
Clause 13.4.4 (EN p.102): the pressure at the hydraulically most unfavourable sprinkler shall be not less than that required to give the density specified in 13.4.1, or than the following values, whichever is the higher: 0.70 bar in LH; 0.35 bar in OH; 0.50 bar in HHP and HHS excluding in-rack sprinklers; 1.00 bar for K115 in-rack sprinklers; 2.00 bar for K80 in-rack sprinklers. The note to Clause 7.2.3.4 states a minimum pressure of 2.0 bar at any operating sprinkler and refers to 13.4.4; the two places must be read together.
How many racks and how many levels are assumed to operate at once in the hydraulic calculation?
Clause 7.2.3.3 (EN p.37): at each in-rack sprinkler level, 3 sprinklers are assumed to operate simultaneously in the hydraulically most remote position, up to a maximum of three levels. Where the rack aisles are 2.4 m or wider, only one rack is assumed to be involved; where the aisles are narrower than 2.4 m but equal to or wider than 1.2 m, two racks; where the aisles are narrower than 1.2 m, three racks.
Are water shields required on intermediate level sprinklers?
Clause 14.7 (EN p.106): sprinklers installed in racks or below perforated shelves, platforms, floors and the like, where water from one or more sprinklers higher up could wet the area near the bulb or fusible element, are provided with a metal water shield at least 0.075 m in diameter. Water shields on upright sprinklers are not connected directly to the deflector or to the yoke, and any bracket supports are designed to minimize obstruction to the sprinkler water distribution. The standard does not exempt the top level.
References
- TS EN 12845+A2:2026 Table 2 and its footnotes (EN p.34)
- TS EN 12845+A2:2026 Clauses 7.2.2.2, 7.2.2.3 (EN p.36-37)
- TS EN 12845+A2:2026 Clauses 7.2.3.1, 7.2.3.2, 7.2.3.3, 7.2.3.4 (EN p.37)
- TS EN 12845+A2:2026 Table 4 (EN p.38), Table 5 (EN p.39)
- TS EN 12845+A2:2026 Clause 12.1.2 (EN p.70), Clause 12.3 (EN p.72)
- TS EN 12845+A2:2026 Clauses 12.5.1, 12.5.2, 12.5.3 (EN p.78)
- TS EN 12845+A2:2026 Figure 13 (EN p.79), Figure 14, Clauses 12.5.4, 12.5.5 (EN p.80)
- TS EN 12845+A2:2026 Clause 12.5.6, Figure 15 (EN p.81), Table 21 (EN p.82)
- TS EN 12845+A2:2026 Clause 13.1 (EN p.82), Clauses 13.4.1, 13.4.4 (EN p.98-102)
- TS EN 12845+A2:2026 Clauses 14.2.1, 14.2.2, Table 37a (EN p.104)
- TS EN 12845+A2:2026 Clause 14.5.1, Table 38, Clause 14.7 (EN p.106)
- TS EN 12845+A2:2026 Annex B (EN p.127-131), Annex P (EN p.164)
- TS EN 12845-2:2024 Contents and Clause 6.6.2
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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.