In sprinkler design the question "which mode" is not a preference but an outcome permitted by the text of the standard. This article compares the three modes from two sources only: TS EN 12845-2:2025 (EN 12845-2:2024), for ESFR and CMSA; TS EN 12845+A2:2026 (EN 12845:2015+A2:2026), for CMDA. Every value in the comparison is given together with its clause or table number and EN page.
1. Definitions: how the standard separates the three modes
The Introduction of EN 12845-2 (EN p.4) defines the three concepts directly:
- ESFR (early suppression fast response): sprinklers conforming to EN 12259-13 that operate in suppression mode, that is, they are capable of typically suppressing fires significantly (reducing the heat release rate) in storage risks. Designs are typically defined by k-factors, numbers of operating heads and required head pressures.
- CMSA (control mode specific application): sprinklers that operate in control mode, that is, they are capable of controlling fires (limiting the heat release rate) in storage risks. They are used in specific challenging storage scenarios where alternative approaches are not considered suitable. Designs are typically defined by the number of operating heads and the required head pressure.
- CMDA (control mode density area): sprinklers that operate in control mode in accordance with EN 12845-1, typically conforming to EN 12259-1. Designs are typically defined by a minimum water "density" (mm/min) to be applied over a defined area of operation.
The same section adds this as well: the ESFR sprinkler concept is a technical development derived from CMSA sprinklers; ESFR and CMSA designs are less capable of coping with adverse design features and non-conformities, and it is particularly important that all the requirements of this standard are complied with without exception.
The link between the two standards is established on the EN 12845+A2 side as well: Annex N (normative, EN p.162) for CMSA systems and Annex P (normative, EN p.164) for ESFR systems state that "EN 12845-2 shall be applied together with this document" and refer to Annex A of EN 12845-2:2024 for the class conversion.
2. How the design is expressed
| CMDA | CMSA | ESFR | |
|---|---|---|---|
| How the design is given | Density (mm/min) × area of operation (m²) | Number of sprinklers @ minimum pressure (bar) | Number of sprinklers @ minimum pressure (bar) |
| Main design tables | Table 3 (LH/OH/HHP), Tables 4 and 5 (HHS) | Tables 15-21 (general), Tables 22-25 (special products) | Tables 7-9 (ceiling only), Tables 10-11 (conditional), Tables 12-14 (in-rack) |
| Source | TS EN 12845+A2, EN p.36, 38, 39 | EN 12845-2, EN p.49-58 | EN 12845-2, EN p.36-47 |
Example values on the CMDA side (Table 3, Clause 7.1, EN p.36): LH 2.25 mm/min and 84 m²; OH1 5.0 mm/min and 72 m²; OH2 5.0 mm/min and 144 m²; OH3 5.0 mm/min and 216 m²; OH4 5.0 mm/min and 360 m²; HHP1 7.5 mm/min, HHP2 10.0 mm/min, HHP3 12.5 mm/min, all three over 260 m². For HHP4 there is a note reading "deluge, special consideration required, not within the scope of this standard".
Example values on the ESFR side (Table 7, Clause 6.6.1.1, EN p.36): HHS1-HHS3, for a 9.1 m ceiling / 7.6 m storage, K200 pendent 3.4 bar, K240 2.4 bar, K320 1.7 bar, K360 1.0 bar; the same classes for a 10.7 m ceiling / 9.1 m storage, K200 5.2 bar, K240 3.6 bar, K320 2.4 bar, K360 1.4 bar. The designs in Table 7 are generally based on the operation of 12 heads.
Example values on the CMSA side (Table 16, Clause 6.7.1, EN p.50): HHS3, for 7.6 m storage / 9.1 m ceiling, K240 upright 15 sprinklers @ 1.5 bar, K280 pendent 15 @ 1.1 bar, K360 pendent 15 @ 0.7 bar, K360 upright 12 @ 1.4 bar.
3. K factors
The k-factors for CMDA are limited by TS EN 12845+A2 Table 37a (Clause 14.2.1, EN p.104):
| Hazard class | Design density | Nominal K-factor |
|---|---|---|
| LH | 2.25 mm/min | 57 |
| OH | 5.0 mm/min | 80 or 115 |
| HHP and HHS ceiling/roof sprinklers | ≤10 mm/min | 80, 115 or 160 |
| HHP and HHS ceiling/roof sprinklers | >10 mm/min | 115 or 160 |
| HHS intermediate level sprinklers in high stack storage | - | 80 or 115 |
On the EN 12845-2 side, the k-factors are read from the design tables: for ESFR, Tables 7-11 contain K200, K240, K320, K360, K400 and K480 columns (EN p.36-41); for CMSA, Tables 15-25 use K160, K240, K280, K360 and K480 (EN p.49-58).
The flow rate comes from the same formula in all three modes: Q = K√P (TS EN 12845+A2 Clause 14.3, EN p.104-105); Q in l/min, K the constant from Table 37a, P in bar.
4. Pressures
In CMDA the design pressure is given not as a single range but as a minimum discharge pressure (Clause 13.4.4, EN p.102): the pressure at the hydraulically most unfavourable sprinkler shall not be less than the value required to achieve the density specified in 13.4.1, or than the following, whichever is the higher:
- 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
In EN 12845-2 the pressure is read directly from the design tables. The extreme values found in the tables: in CMSA the lowest is 0.5 bar (Table 17, HHS1/HHS2, K360 upright dry, 20 sprinklers, EN p.51) and the highest is 5.2 bar (Table 22 rubber tyres, K160 upright 15 sprinklers, EN p.57); in ESFR the lowest is 1.0 bar (Table 7, K360, EN p.36) and the highest is 6.9 bar (Table 10, HHS5, K200, 12 sprinklers, EN p.41). Clause 5.4 (EN p.33) also gives the minimum operating pressure for the 12 sprinkler HHS5 design directly: 2.0 bar up to a storage height of 7.6 m / ceiling 9.1 m, and 4.1 bar up to storage 10.7 m / ceiling 12.2 m.
5. Number of sprinklers, shape of the design area and duration
EN 12845-2 Table 6 (Clause 6.4, EN p.34) gives three pieces of information together:
| Number of ceiling sprinklers | Water supply duration (min) | Shape of design area (sprinklers × range pipes) |
|---|---|---|
| 9 | 60 | 3 × 3 |
| 10 | 60 | 3 × 2 + 4 × 1 |
| 12 | 60 | 4 × 3 |
| 15 | 90 | 5 × 3 |
| 16 | 90 | 5 × 3 + 1 × 1 |
| 20 | 120 | 5 × 4 |
| 24 | 120 | 6 × 4 |
| 25 | 120 | 6 × 4 + 1 × 1 |
| 30 | 120 | 7 × 4 + 2 × 1 |
NOTE 2: with CMSA in roll paper storage the duration shall be 120 min irrespective of the number of sprinklers. NOTE 3: with CMSA in rubber tyre storage the duration shall be 180 min. Table 21 (EN p.55) also contains special dry pipe designs with 36 sprinklers, and that table carries its own system duration column (90 or 120 min).
In CMDA the duration is tied not to the number of sprinklers but to the hazard class (Clause 8.1.1, EN p.42): LH 30 min, OH 60 min, HHP 90 min, HHS 90 min.
6. Layout and response characteristic
| Topic | CMDA (TS EN 12845+A2) | ESFR (EN 12845-2) | CMSA (EN 12845-2) |
|---|---|---|---|
| Maximum coverage area | LH 21.0 m², OH 12.0 m², HHP and HHS 9.0 m² (Table 19, EN p.70) | 9.3 m² (5.1.3.2, EN p.8) | 12 m² in certain ceiling cases in STC1, 9.3 m² in all other cases (5.1.3.3, EN p.8) |
| Minimum coverage area | Not given | 6 m² (5.1.3.2) | 7.5 m² (5.1.3.3) |
| Minimum distance between sprinklers | 2 m (12.3, EN p.72) | 2.4 m (5.1.3.2) | 2.4 m (5.1.3.3) |
| Maximum spacing | LH 4.6 m, OH 4.0 m, HHP/HHS 3.7 m (Table 19) | 3.7 m with a ceiling ≤9.1 m; 3.1 m above 9.1 m | 3.7 m; 3.1 m with combustible obstructed construction |
| Distance to wall | The smallest suitable value in accordance with 12.4.1 (EN p.72) | ≤50% of the maximum permitted spacing | ≤50% of the maximum permitted spacing |
| Deflector below ceiling | Preferably 0.075-0.15 m; where unavoidable ≤0.3 m with a combustible ceiling, ≤0.45 m with an A1/A2 ceiling (12.4.2, EN p.72) | At least 100 mm; maximum 325 or 425 mm according to Table 2 (5.1.3.5.2, EN p.9-10) | At least 100 mm; maximum 225-325 mm unobstructed and 325 mm obstructed according to Table 2 |
On the response characteristic, EN 12845-2 Clause 5.1.1 NOTE 2 (EN p.8) says only this: ESFR typically has a nominal operating temperature of 68 °C to 74 °C and is quick response; CMSA is also typically 68 °C to 74 °C, except in dry systems where it is generally 141 °C. The standard gives no numerical RTI value. On the CMDA side the classification is made by Table 38 (Clause 14.5.1, EN p.106): quick response, special response and standard 'A' response; according to the table, quick response sprinklers are not used in dry systems, and in racks only quick response sprinklers are used.
7. Limits of applicability: who chooses the mode
The standard does not tabulate the choice of mode by stack height. Instead it sets exclusions and preconditions:
- EN 12845-2 Clause 4 (EN p.6): ESFR sprinklers shall be used in wet installations only. CMSA sprinklers may be used in wet and dry installations. Open-top containers shall not be used in storage hazards protected by ESFR or CMSA unless specifically stated otherwise in a clause of the standard.
- Clause 5.1.1 (EN p.8): the design criteria in 6.6 and 6.7 are valid provided that the sprinkler has been successfully tested for the intended ceiling height, storage height, commodity and storage type.
- Clause 6.1 (EN p.33): the design shall be based on the design tables in Clause 6; interpolation and extrapolation are not permitted. Where more than one single pallet load of a higher category is stored within any 300 m², the design is based on that higher category. Goods not covered by the design tables (for example flammable liquids, aerosols and their single pallet loads) shall not be protected in accordance with this document; instead, EN 12845 shall be applied where applicable.
- Clause 6.2 (EN p.33): ESFR and CMSA protection shall not be applied to FH3 to FH5 occupancies. Where they are used in FH1 and FH2 hazards, they are designed as HHS1 to HHS3 in accordance with 6.6 or 6.7, irrespective of the storage category.
- Annex A Table A.1 (EN p.59): the FH equivalents of the EN 12845:2015 classes: LH and OH1 → FH1; OH2 and OH3 → FH2; OH4 → FH3; HHP1 and HHP2 → FH4; HHP3 → FH5.
Read together, these two provisions mean that ESFR and CMSA cannot be applied in areas classified as OH4 or higher under the EN 12845:2015 classification.
On hazard classes, the classification on the CMDA side also has clear limits: Clause 6.2.2 (EN p.31) defines LH as occupancies with low fire load and low combustibility, no single compartment exceeding 126 m² and a fire resistance of at least 30 min; Clause 6.2.3 (EN p.31) permits storage in OH areas only where the room as a whole is designed to at least OH3, the maximum storage heights in Table 1 are complied with, the area of a single block does not exceed 50 m² and there is a clearance of at least 2.4 m around the block.
Field note: Although the three modes appear to be alternatives to one another, the text of the standard places them behind different doors: first the occupancy and hazard class, then the storage configuration and height, then whether the commodity appears in a table row at all. If there is no table row, there is no mode.
Frequently Asked Questions
What is the fundamental difference between CMDA, CMSA and ESFR?
TS EN 12845-2:2025 Introduction, EN p.4: ESFR operates in suppression mode, that is, it is capable of significantly suppressing the heat release rate of a fire; the design is given by the k-factor, the number of operating heads and the required head pressure. CMSA operates in control mode; the design is given by the number of operating heads and the required pressure. CMDA operates in control mode in accordance with EN 12845-1 and its design is given by a minimum water application density (mm/min) over a defined area of operation.
Which K factors are used in the three modes?
For CMDA, TS EN 12845+A2:2026 Table 37a (EN p.104): LH K57; OH K80 or K115; HHP and HHS ceiling sprinklers K80, K115 or K160 where the density is ≤10 mm/min and K115 or K160 where it is >10 mm/min; HHS intermediate level sprinklers K80 or K115. For ESFR, EN 12845-2 Tables 7-11 (EN p.36-41) give values from K200 to K480; for CMSA, Tables 15-25 (EN p.49-58) give values from K160 to K480.
How many sprinklers are assumed to operate in each mode?
EN 12845-2 Table 6 (EN p.34) lists the number of sprinklers in the ceiling design as 9, 10, 12, 15, 16, 20, 24, 25 and 30; Table 21 (EN p.55) also contains 36 sprinkler designs. For CMDA the number is not given directly; TS EN 12845+A2 Table 3 (EN p.36) gives density and area of operation, e.g. 5.0 mm/min and 216 m² for OH3.
Can ESFR and CMSA be used in every hazard class?
No. EN 12845-2 Clause 6.2 (EN p.33): ESFR and CMSA protection shall not be applied to FH3 to FH5 occupancies. Where they are used in FH1 and FH2 hazards, they are designed as HHS1 to HHS3 in accordance with 6.6 or 6.7, irrespective of the storage category. In addition, Clause 6.1 (EN p.33) states that goods such as flammable liquids and aerosols shall not be protected in accordance with this document and that EN 12845 applies instead.
How are the water supply durations determined?
For ESFR and CMSA, EN 12845-2 Table 6 (EN p.34) ties the duration to the number of sprinklers: 9-12 sprinklers 60 min, 15-16 sprinklers 90 min, 20-30 sprinklers 120 min. NOTE 2: with CMSA in roll paper storage the duration is 120 min irrespective of the number of sprinklers; NOTE 3: with CMSA in rubber tyre storage it is 180 min. For CMDA, TS EN 12845+A2 Clause 8.1.1 (EN p.42): LH 30 min, OH 60 min, HHP 90 min, HHS 90 min.
References
- TS EN 12845-2:2025 (EN 12845-2:2024), Introduction - definitions of ESFR, CMSA and CMDA (EN p.4)
- TS EN 12845-2:2025, Clause 4 General (EN p.6)
- TS EN 12845-2:2025, Clause 5.1.1 and NOTE 2, Clauses 5.1.3.2, 5.1.3.3 (EN p.8)
- TS EN 12845-2:2025, Table 2 (EN p.10)
- TS EN 12845-2:2025, Clause 5.4 HHS5 12 sprinkler design (EN p.32-33)
- TS EN 12845-2:2025, Clauses 6.1 and 6.2 (EN p.33)
- TS EN 12845-2:2025, Clause 6.4 and Table 6 (EN p.34)
- TS EN 12845-2:2025, Clause 6.6.1.1 and Table 7 (EN p.35-36)
- TS EN 12845-2:2025, Tables 10 and 11 (EN p.41)
- TS EN 12845-2:2025, Clause 6.7.1 and Tables 15-21 (EN p.48-55)
- TS EN 12845-2:2025, Table 22 (EN p.57)
- TS EN 12845-2:2025, Annex A Table A.1 (EN p.59)
- TS EN 12845+A2:2026, Clauses 6.2.2 and 6.2.3 (EN p.31)
- TS EN 12845+A2:2026, Clause 7.1 and Table 3 (EN p.35-36)
- TS EN 12845+A2:2026, Clause 8.1.1 (EN p.42)
- TS EN 12845+A2:2026, Table 19 and Clauses 12.3, 12.4.1, 12.4.2 (EN p.70-72)
- TS EN 12845+A2:2026, Clause 13.4.4 (EN p.102)
- TS EN 12845+A2:2026, Table 37a and Clause 14.3 (EN p.104-105)
- TS EN 12845+A2:2026, Clause 14.5.1 and Table 38 (EN p.106)
- TS EN 12845+A2:2026, Annex N (EN p.162) and Annex P (EN p.164)
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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.