CMSA — Control Mode Specific Application Sprinklers

CMSA bridges the gap between ESFR and classical CMDA — large droplets, moderate pressure, listed for a specific commodity. Its older name was the "large drop sprinkler". Where roof slope or skylights rule ESFR out, CMSA is very often the only practical answer. It is EN 12845-2's plan B.

A tyre distribution warehouse was planned with ESFR at ceiling. The roof, however, had a 7 % slope for drainage runs, plus a 6 m² skylight every 200 m² — breaching both the 5 % slope limit and the 5 m² skylight limit for ESFR. The solution was CMSA K160 at ceiling plus in-rack at every level. Water demand rose to about 1.2 times the ESFR figure, but the design was properly listed and the insurer accepted it. CMSA means that when ESFR is not available there is still a modern answer — and for a designer who knows it, that is a rescue.

How CMSA came about

In the 1980s the "large drop sprinkler" was developed alongside ESFR. ESFR aimed at suppression; the large drop head aimed at control through large droplets — less sensitive, more flexible. It was formalised in NFPA 13 as CMSA in 1991, and EN 12845-2:2024 brought the same concept into the European standard.

CMSA product characteristics

• K-factors K115, K160, K200 and K240
• RTI of 50–80, between ESFR's 50 and the 200 of a standard-response head
• Operating pressure 2–4 bar
• Sprinkler spacing 2.4–3.7 m
• Coverage 9–12 m² per head
• "Specific application" — listed for a named commodity and storage arrangement
• Listing bodies: FM, UL, VdS, LPCB

ESFR versus CMSA

Aspect	ESFR	CMSA
Objective	Suppression	Control by large droplets
K-factor	K200–K480	K115–K240
Pressure	3.5–5.2 bar	2–4 bar
RTI	≤ 50	50–80
Design sprinklers	12	15–30
Roof slope	≤ 5 %	≤ 17 % (flexible)
Skylights	≤ 5 m²	≤ 10–15 m²
Obstructions	Strict	More forgiving
In-rack	Usually not needed	Frequently combined
Water demand	Lower, over 60 min	Moderate, over 60–90 min

Typical CMSA commodities and designs

Commodity	Storage height	K	Pressure	Design heads
Tyre storage	≤ 6 m	K160	3.5 bar	20
Paper rolls on end	≤ 8 m	K200	3.0 bar	15
Class III standard	≤ 7.6 m	K160	2.4 bar	15
Group A plastics	≤ 6 m	K200	3.5 bar	15–20
Idle timber pallets	≤ 6 m	K160	3.0 bar	15

CMSA combined with in-rack protection

For high-bay storage above about 9 m, CMSA at ceiling plus in-rack at every level is the standard solution:

• Ceiling: CMSA K160–K200, with 15–20 design heads
• In-rack: K80–K115 at 3 m spacing on each level
• Total demand: the ceiling design area plus the six worst-case in-rack heads
• Hydraulic balance: ceiling pressure must not starve the in-rack branch
• Water shields at each level, so an upper head does not cool the one below

Field error — no listing for the actual commodity

A paper roll distribution warehouse specified CMSA K200 heads, but the manufacturer's listing had no "rolled paper, vertical, ≤ 8 m" configuration — it read only "Class III commodities". The insurer's audit recorded a specific-application mismatch, and the heads were replaced with a model listed for paper rolls. In CMSA, "specific application" is the operative phrase: the listing must state the commodity and the storage geometry explicitly.

Features of the hydraulic calculation

• Design area typically the most remote 4 rows × 4 sprinklers, i.e. 16 heads
• Minimum operating pressure must reach every design head
• Pipe diameters larger than for CMDA, because the flow is higher
• A double-ended feed to the distribution pipework is recommended
• Insurers require a calculation report from recognised software
• EN 12845-2 Annex O gives a worked example

Placement rules

• Sprinkler spacing 2.4–3.7 m
• Coverage ≤ 9–12 m² depending on the commodity
• At least 100 mm from a wall, at most half the spacing
• Deflector 0.15–0.5 m below the ceiling
• Roof slope ≤ 17 % — far more forgiving than ESFR
• Skylights ≤ 10–15 m²
• Obstruction rules more relaxed than ESFR, per the manufacturer's instructions

Foam-water CMSA

For flammable liquid storage (Class IB–II), CMSA combined with AFFF foam is common: open heads, a deluge valve and foam concentrate proportioning. Several manufacturers offer listed CMSA ranges aimed specifically at tyre storage, paper rolls, plastics and Class III commodities, and the foam-water variants are listed separately from the wet-pipe versions.

Alignment with NFPA 13

The CMSA section of EN 12845-2 aligns closely with NFPA 13. K-factor values are equivalent (K11.2 corresponds to K160), and the spacing and pressure tables are similar. On Turkish projects, internationally insured clients typically work to NFPA 13 plus the relevant FM Global data sheets, while domestic insurers accept EN 12845-2 on its own.

Turkish regulation and local practice

BYKHY has no separate CMSA provision; the EN 12845 reference covers it. TS EN 12845-2:2024 is published, and in practice the designer makes the selection. CMSA with foam-water is common in Turkish tyre warehouses, and CMSA for paper rolls is standard in the paper and packaging sector.

Quick check list

• The reason for choosing CMSA over ESFR is documented.
• The manufacturer's listing matches the commodity and storage geometry.
• K-factor, pressure and design head count match the table.
• In-rack hydraulics balanced against the ceiling system.
• Roof slope ≤ 17 %.
• Spacing, deflector position and obstruction rules checked.
• Foam-water system listed, where used.
• Hydraulic report ready for the insurer.

Frequently Asked Questions

What is CMSA?

Control Mode Specific Application — a large-droplet sprinkler listed for a named commodity and storage arrangement. It was formerly known as the large drop sprinkler.

When would you choose CMSA over ESFR?

Whenever the building rules ESFR out: roof slope above 5 %, skylights larger than 5 m², or obstructions ESFR cannot tolerate. CMSA accepts up to 17 % slope and much larger skylights.

Does CMSA need in-rack sprinklers?

Above about 9 m storage, yes — CMSA at ceiling plus in-rack at each level is the standard arrangement, with water shields so an upper head does not cool the one below.

What does "specific application" actually mean?

That the listing names the commodity and the storage geometry. A head listed for "Class III commodities" does not automatically cover vertical paper rolls, and insurers do check.

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