All three are sprinklers, but each carries a different fire philosophy. CMDA controls the fire by wetting it, CMSA controls it by overcoming the fire plume with large droplets, and ESFR aims to suppress it outright. Choosing the wrong mode changes the pump pressure, the tank volume and the rack design together.
The distinction in one line each
- CMDA (Control Mode Density/Area): "Apply this many mm/min over this area." The classic density-area approach.
- CMSA (Control Mode Specific Application): "Operate this many sprinklers at this pressure." Large droplets; the number of sprinklers and the minimum pressure come from the standard's tables by commodity, storage height and ceiling height.
- ESFR (Early Suppression Fast Response): "Detect early, apply water early and hard, suppress." Large K-factor and fast response (RTI 50 (m·s)½ or less; NFPA 13 3.3.223.4.5).
Side by side
Values are from the NFPA 13-2025 tables; where EN 12845-2:2024 differs, it is stated.
| Parameter | CMDA | CMSA | ESFR |
|---|---|---|---|
| Objective | Control | Control | Suppression |
| Design input | Density × area | Sprinkler count × minimum pressure | 12 sprinklers (4 × 3) × minimum pressure (NFPA 23.2.2) |
| K-factor | Typically K5.6–K11.2 (K80–K160) | K11.2–K25.2 (K160–K360) (Tables 22.2–22.5); EN 12845-2 also has K33.6 (K480) on dry systems | K14–K25.2 (K200–K360) (Table 23.3.1); EN 12845-2 Table 7 also has K28 (K400) and K33.6 (K480) |
| Minimum operating pressure | Calculated from density and K-factor | 0.7–5.2 bar (Table 22.4) | 1.0–5.2 bar (Table 23.3.1) |
| Sprinklers in the design | Derived from the design area | Mostly 15 on wet (20 in some options); 25–36 on dry (Table 22.4) | 12 (4 × 3) |
| Response | Typically standard response | Quick or standard response (NFPA 22.1.1–22.1.2) | Fast response |
| Max ceiling slope | More flexible | 4 in 12 (≈18.4°; NFPA 13.2.1.2); EN 12845-2: 10° (5.2.1) | 4 in 12 (≈18.4°; NFPA 14.2.3); EN 12845-2: 10° (5.2.1) |
| In-rack sprinklers | Required for racks over 7.6 m (NFPA 21.4.2.1 → Chapter 25) | Required in some table options | Usually unnecessary (except solid shelving) |
| On a dry system | Permitted | Permitted (where the table has a dry option) | Wet only (NFPA: except specific listings; EN 12845-2: no dry installation option, an installation with dry pendent ESFR is treated as wet, propylene glycol designs with K320 or larger and tree pipework may be used, 6.5) |
| Water supply duration (NFPA Table 20.15.2.6) | 60–150 min by design area | 60–150 min by sprinkler count (13–15 sprinklers: 90 min) | 60 min up to 12 sprinklers |
A numerical comparison on 9 m storage
Under NFPA 13-2025: rack storage, Class III commodity, 9 m storage height, 12 m ceiling, wet system. Flows are calculated from the minimum pressure at each sprinkler (Q = K·√P); hydraulic imbalance is not included, so the real demand is higher.
| Mode and basis | Sprinkler demand | Hose allowance | Total flow | Duration | Water volume | In-rack |
|---|---|---|---|---|---|---|
| CMDA plus in-rack (Figure 25.4.3.1.1.2(a)–(g): 12.2 mm/min over 185 m², ordinary temperature; in-rack 10 × 114 L/min) | 2,257 + 1,140 = 3,397 L/min | 1,900 L/min | ≈ 5,300 L/min | 120 min | ≈ 636 m³ | Required (at most 3.0 m of storage above the top in-rack level) |
| CMSA, ceiling only (Table 22.4: K25.2 (K360) pendent, 15 sprinklers, 1.6 bar) | 15 × 455 = 6,830 L/min | 1,900 L/min | ≈ 8,730 L/min | 90 min | ≈ 786 m³ | None |
| ESFR, ceiling only (Table 23.3.1: K25.2 (K360) pendent, 12 sprinklers, 1.7 bar) | 12 × 469 = 5,630 L/min | 950 L/min | ≈ 6,580 L/min | 60 min | ≈ 395 m³ | None |
Three lessons from that table: thanks to its 60-minute duration and smaller hose allowance, ESFR needs the smallest water volume; CMSA produces the highest flow and the largest tank; CMDA has a low ceiling flow but leaves you carrying the in-rack maintenance burden for the life of the building. The pump pressure depends on the pipe network and elevation and comes from the hydraulic calculation.
Decision tree
- Storage up to 4 m, light or ordinary hazard → CMDA. No argument needed.
- Storage of 4 to 7 m, or a specific commodity such as rubber tyres or paper rolls → CMSA.
- Storage of 6 m or more, suitable ceiling slope, limited skylights, wet system → ESFR.
- Ceiling slope above 4 in 12 (NFPA) or 10° (EN 12845-2) → neither ESFR nor CMSA can be applied directly; consider a flat false ceiling or the in-rack solution (EN 12845-2 5.2.1), or CMDA plus in-rack.
- Cold store or freezing risk → ESFR is out (unless an ESFR specifically listed for dry or preaction use exists under NFPA; EN 12845-2 has no dry installation option, but unheated areas may use dry pendent ESFR (treated as a wet installation) or a propylene glycol design with K320 or larger and tree pipework, 6.5).
- Open-top containers → ESFR is not permitted (NFPA 23.1.3.2). Solid shelf racking → ESFR only together with in-rack sprinklers to Chapter 25 (23.1.3.1).
The design height trap: an ESFR design is valid only up to a defined maximum storage and ceiling height (NFPA Table 23.3.1). If the racking rises five years later the design is no longer valid, and the insurer will raise that at a claim. A five-year growth projection belongs in the design.
Maintenance and life cost
ESFR's strongest feature is that the sprinklers are only at ceiling level: no entering the racking, no emptying product, no hunting for a damaged sprinkler. CMSA and CMDA with in-rack branches create an access problem every year. Over ten years of total ownership cost, ESFR comes out ahead in most warehouses; on first cost it falls behind, because of the pump and the pipe sizes.
Frequently Asked Questions
What is the basic difference between ESFR and CMSA?
ESFR aims at suppression; in NFPA 13 the design is generally based on the most demanding 12 sprinklers (23.2.2) at minimum pressures of 1.0 to 5.2 bar from Table 23.3.1. CMSA controls the fire, mostly with 15 sprinklers on wet systems and 25 to 36 on dry systems, at 0.7 to 5.2 bar from Table 22.4. In both modes the criteria are taken from the standard's tables by commodity class, storage height and ceiling height.
When is ESFR ruled out?
Where the ceiling slope exceeds 4 in 12 (about 18.4°; NFPA 13 14.2.3) or 10° under EN 12845-2 (5.2.1); with open-top containers (NFPA 23.1.3.2); in spaces at risk of freezing (unless an ESFR specifically listed for dry or preaction use is available); on solid shelf racking unless in-rack sprinklers are added (23.1.3.1); and where the clearance between sprinklers and the top of storage falls below 900 mm in NFPA (14.2.11) or 1 m in EN 12845-2 (5.1.3.7).
Which mode is cheapest?
Usually CMDA on first cost, because the pump and pipe sizes are smaller. But over ten years ESFR comes out ahead in most warehouses, because there is no in-rack sprinkler maintenance.
Can ESFR be used on a dry system?
Under NFPA 13 14.2.2 ESFR is used on wet systems; ESFR sprinklers specifically listed for dry or preaction use are the exception. Under EN 12845-2 ESFR is used on wet systems only. Specifically listed dry-type ESFR products are limited and the water demand increases.
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Download MEP Calc on the App StoreNFPA 13 (2025) Chapter 14 and the storage chapters (20–25). EN 12845:2015+A2:2026 and EN 12845-2:2024. EN 12259-13 (ESFR sprinklers). FM Global DS 8-9. Values are for information only.