EN 12845-2:2024 Overview — ESFR and CMSA

Classical EN 12845 "controls" a fire and buys the fire service time. EN 12845-2 "suppresses" it — ESFR and CMSA designs reach the flame front through early operation and large droplets. For a modern logistics facility with high storage, plastics and automation, this standard is no longer optional.

In the 1980s, full-scale high-bay warehouse fire testing established that conventional CMDA sprinklers did not extinguish the fire — they wetted the surroundings and bought time. As long as the fire jumped from pallet to pallet, the sprinklers were only keeping pace. The answer was early operation (RTI below 50), high pressure and large droplets striking the flame front directly. ESFR was the result, and it entered NFPA 13 in 1991. European development began in 2009 through CEN/TC 191, with EN 12259 covering sprinkler products and EN 12845 the design. In 2024 the design provisions were published as the separate document EN 12845-2.

EN 12845-1 versus EN 12845-2

Aspect	EN 12845-1	EN 12845-2
Design mode	CMDA (control)	CMSA plus ESFR (suppression)
Sprinkler type	Standard, K57–K115	K200–K360 large orifice
Response (RTI)	≥ 80 (standard)	≤ 50 (fast)
Design basis	Design area of 260–360 m²	12 sprinklers
Objective	Control the fire perimeter	Extinguish the fire
Typical pressure	1–3 bar	3.5–5.2 bar
Water demand	About 30–60 m³	50–150 m³ over 60 min

The structure of EN 12845-2

1. Scope: ESFR and CMSA design, hydraulics and installation
2. Normative references: EN 12259, EN 1568, ISO 6182
3. Terms and definitions
4. General requirements covering structure, roof and racking
5. ESFR design criteria: K-factor, pressure and design area
6. CMSA design criteria
7. Hydraulic calculation
8. Sprinkler placement: deflector position and obstructions
9. Water supply and pumps
10. Commissioning and testing
11. Maintenance, running parallel to the EN 12845-1 maintenance clauses
12. Annex N: CMSA detail
13. Annex O: P&ID and hydraulic examples
14. Annex P: ESFR detail

The ESFR principle

An ESFR sprinkler has four critical characteristics:

• Early operation: RTI ≤ 50, so the fire is detected within 30–60 s
• High flow: a K200–K360 large orifice, delivering 250–1500 L/min per head
• High droplet velocity: 3.5–5.2 bar produces droplets at 6–8 m/s that reach the flame front
• Wide coverage: 9 m² per head, so a limited number of operating heads (12) is sufficient

Typical suppression time is 60–90 s. The water strikes the fire cell directly and extinguishes the flame, saving the warehouse before the fire service arrives.

The CMSA principle

CMSA sits between the two — an alternative to ESFR, stronger than the classical approach:

• K115–K200 large orifice
• RTI between 50 and 80, between standard and fast response
• Operating pressure of 2–4 bar
• "Specific application" — the design is matched to a named commodity
• Fire control, and sometimes suppression
• Chosen where ESFR is unavailable or unsuitable

Its former name was the large drop sprinkler, developed in the United States in the 1980s and adopted under its modern name in EN 12845-2.

When is EN 12845-2 required?

• Block storage above 6 m — or 4 m for some commodities
• Group A plastic storage above 3 m
• Tyre storage above 3.7 m
• Level 3 aerosol storage
• Whisky or spirit bond houses in wooden casks
• Automotive spare parts logistics, with high plastic content
• High-bay e-commerce warehouses
• Wherever the insurer requires it

A practical decision matrix

Storage height	Commodity	Recommended design
≤ 4 m	Standard	EN 12845-1 OH/HHS
4–6 m	Standard	EN 12845-1 HHS plus in-rack
≥ 6 m	Standard	EN 12845-2 ESFR
≥ 3 m	Group A plastics	EN 12845-2 ESFR
≥ 3.7 m	Tyres or flammable liquids	EN 12845-2 CMSA with foam
≤ 7 m	Semi-combustible	EN 12845-2 CMSA alone

Field error — the ESFR roof slope limit was skipped

An e-commerce warehouse was designed with ceiling ESFR. The roof slope was actually 8 %, laid in for long drainage runs, against a design assumption of 5 %. Under a sloped ceiling the hot gas layer slides sideways and the sprinklers heat up late. EN 12845-2 sets a 5 % maximum; where it is exceeded, either a draft curtain or a CMSA alternative is required. The insurer's audit caught it, and since the roof geometry could not be changed the project moved to CMSA with foam, at roughly 20 % higher cost.

Transitional rules for existing projects

• New projects after 2024: EN 12845-2 is the basis
• Designed before 2024 but built in 2024: the designer may choose Part 1 or Part 2
• Existing installations: no mandatory update
• Major modification, such as a capacity increase or commodity change: EN 12845-2 is assessed
• Insurance renewal: the insurer may require the update
• Rebuilding after a loss: the new standard is mandatory

Application in Turkey

TS EN 12845-2:2024 has been published by the Turkish Standards Institution. BYKHY references EN 12845, and in practice Parts 1 and 2 are applied together. ESFR design is becoming widespread in Turkey's logistics hubs. In domestic manufacturers' warehouses, EN 12845-1 at OH3 to HHS still dominates, and insurer audits commonly call for an upgrade.

Quick check list

• The standard reference (Part 1, Part 2 or both) is stated in the design documents.
• Storage height and commodity assessed against the need for ESFR or CMSA.
• Roof slope no more than 5 % for ESFR.
• Skylight and ventilation areas within limits.
• Hydraulic calculation follows the Annex O examples.
• Commissioning aligned with the EN 12845-1 commissioning clause.
• Maintenance follows the EN 12845-1 clauses together with Annex Q.
• The insurer's accepted standard has been confirmed.

Frequently Asked Questions

What does EN 12845-2 add to EN 12845-1?

Part 1 covers classical CMDA control-mode design. Part 2 adds ESFR and CMSA — suppression-mode design with large orifices, fast response and a fixed twelve-sprinkler design basis.

When does EN 12845-2 become mandatory?

For block storage above 6 m, Group A plastics above 3 m, tyres above 3.7 m, Level 3 aerosols, spirit bond houses, and wherever the insurer requires it.

Do existing installations have to be upgraded?

No. Existing systems carry on, but a major modification, a commodity change, an insurance renewal or a rebuild after a loss all bring EN 12845-2 into play.

What is the biggest practical constraint on ESFR?

Roof geometry. The 5 % slope limit and 5 m² skylight limit rule out ESFR in many existing buildings, which is exactly where CMSA becomes the answer.

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