CMSA: Control Mode Specific Application Sprinkler

CMSA (control mode specific application) sprinklers are the second dedicated storage protection approach defined alongside ESFR in TS EN 12845-2:2025 (EN 12845-2:2024). All the provisions and figures in this article are taken directly from the text of that standard; each value is given together with its clause or table number and EN page.

1. Definition and field of use

The Introduction of the standard (EN p.4): CMSA sprinkler protection uses sprinklers that operate in control mode, that is, sprinklers capable of controlling fires (limiting the heat release rate) within storage risks. CMSA protection tends to be used for various specific challenges in high hazard storage scenarios where alternative approaches are not considered suitable. Designs are typically defined by the number of operating heads and the required head pressure.

The operational meaning of "specific application" is in Clause 5.1.1 (EN p.8): the design criteria given in Clauses 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. NOTE 1 in the same place states that these criteria reflect the results of full scale fire tests carried out at various fire test laboratories.

2. Sprinkler type and temperature rating

Clause 5.1.1 (EN p.7): CMSA pendent, dry pendent or upright sprinklers conforming to prEN 12259-15 shall be used. In dry CMSA systems only dry pendent and upright sprinklers shall be used.

Clause 5.1.1 NOTE 2 (EN p.8): CMSA typically has a nominal operating temperature of 68 °C to 74 °C; dry systems are the exception, where it is generally 141 °C. The nominal operating temperature and response characteristic of the sprinkler are stated in the design tables in Clause 6.

3. Spacing, coverage area and position below the ceiling

Clause 5.1.3.3 (EN p.8):

Clause 5.1.3.4 (EN p.8) allows one exception: in order to prevent installed objects from unacceptably obstructing the discharge, the maximum linear spacing may be extended by not more than 0.3 m in each direction, which permits the maximum area to increase to 10.2 m². This may be applied more than once, but on each occasion the adjacent spacing shall comply with 5.1.3.2 or 5.1.3.3. The standard states explicitly that this is an exception and shall not be applied as normal standard design.

The vertical position below the ceiling is determined by Clause 5.1.3.5.2 and Table 2 (EN p.9-10). Sprinklers are installed with the deflector at least 100 mm below the ceiling. Maximum vertical distance (distance of the thermal element below the ceiling, mm):

Clause 5.1.3.7 (EN p.12): a clear distance of at least 1 m shall be maintained between the ceiling sprinkler deflectors and the top of the storage.

Clause 5.1.3.5.4 (EN p.11-12): CMSA sprinklers with standard response elements shall be installed in each channel formed by the obstructed construction; the exception is where the solid structural members extend not more than 600 mm below the ceiling and one of the following conditions is met: the deflector is installed between 25 mm and 150 mm below a non-combustible solid structural member (where the member extends more than 300 mm below the ceiling, the resulting bays shall not exceed 28 m² and shall not be wider than 0.9 m horizontally); or it is installed 25-100 mm below a combustible member extending 300-525 mm below the ceiling and the bays do not exceed 28 m²; or it is installed 25-150 mm below a non-combustible member extending 300-525 mm below the ceiling, not more than 550 mm below the ceiling, and the bays do not exceed 28 m².

4. Building limits and obstructions

The building limitations applicable to CMSA are shared with ESFR:

• Ceiling slope: maximum 10° (17.6%) (Clause 5.2.1, EN p.12).
• Smoke and heat vents: manually opened vents only; drop-out types prohibited (Clause 5.2.4, EN p.16).
• Air velocity: a 1.5 m/s limit at ceiling level sprinklers (Clauses 5.2.6.1 and 5.2.6.2, EN p.18 and 20).
• Obstructions: Clause 5.3.1 (EN p.21) states explicitly that the obstruction requirements and the requirements for compensating for obstructions for ceiling protection are the same for ESFR and CMSA system designs. Therefore Table 3 (EN p.23), Table 4 (EN p.24) and Table 5 (EN p.26) apply identically to both types.

An additional provision for dry pipe CMSA is in Clause 6.7.2 (EN p.55-56): upright, standard response ceiling level CMSA sprinklers with a nominal rating of 141 °C shall be used in a dead-end dry pipe (tree type) or similar system; gridded or looped systems shall not be used. In pre-action or interlock systems, linear heat detection (LHD) shall be used as the heat detection to initiate the system; the detection line shall be wrapped around the range pipes in order to obtain the same detection pattern as the sprinklers.

5. Design tables

Clause 6.7.1 (EN p.48): Tables 15 to 21 give the design criteria for ceiling only CMSA protection based on the storage and ceiling heights. In dry CMSA designs the water delivery time shall be 40 s with 4 sprinklers operating, unless otherwise stated in the design tables.

Scope of the tables:

Example rows:

• Table 16 (EN p.50): HHS3, storage 7.6 m / ceiling 9.1 m, wet: 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.
• Table 16 (EN p.50): HHS4, storage 6.1 m / ceiling 9.1 m, wet: K160 upright 25 sprinklers @ 1.7 bar or K240 upright 15 @ 1.5 bar.
• Table 22 (EN p.57), wet systems only: rubber tyres on-side or on-tread in STC3, STC4.1 or STC4.2, storage ≤7.6 m / ceiling ≤9.8 m: K160 upright 15 sprinklers @ 5.2 bar or K240 upright 15 @ 2.4 bar.
• Table 23 (EN p.57): heavy roll paper, on-end, standard/closed array, storage ≤7.9 m / ceiling ≤18 m, wet: K160 upright 15 @ 3.4 bar or K240 upright 15 @ 1.5 bar.

6. In-rack sprinklers

In the CMSA ceiling tables, in-rack sprinklers are governed by a table footnote. Table 17, Table 19 and Table 20, footnote a (EN p.51, 53, 54): in the relevant rows, in addition to the ceiling design there is one level of in-rack sprinklers at the first level above the mid-level of the rack, and that level is designed for 8 sprinklers at 115 l/min.

Tables 19 and 20 also carry a footnote b: the relevant row applies only to single row and double row racks and where the aisles are not less than 2.4 m.

7. Duration, design area shape and general design rules

The water supply duration and the shape of the design area are set by Table 6 (Clause 6.4, EN p.34): 60 min for 9-12 sprinklers; 90 min for 15-16 sprinklers; 120 min for 20-30 sprinklers. The design area shape is 4 × 3 for 12 sprinklers, 5 × 3 for 15, 5 × 3 + 1 × 1 for 16, 5 × 4 for 20 and 7 × 4 + 2 × 1 for 30. 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.

The same clause contains two further critical provisions: where the range pipes contain fewer sprinklers than the stated number, all sprinklers are assumed to operate and the number of range pipes concerned is increased to compensate. In addition, a favourable design area is not required and pipe size reduction to limit the demand of a favourable hydraulic area is not permitted.

Clause 6.1 (EN p.33) collects the general design rules: interpolation and extrapolation are prohibited; all flue spaces shall be not less than 150 mm; in STC3 and STC4.3 the distance between loading aisles shall be not more than 6 m; loading aisles shall be at least 1.2 m wide unless the design table requires a greater minimum; for HHS1 and HHS2 the HHS3 protection category shall be used unless otherwise stated; protection for higher categories may be used to protect lower categories; a k-factor design at a given ceiling height may be applied to a lower ceiling height provided no other parameter changes; a clearance of at least 1 m is required from the sprinkler deflector to the top of the stored goods, and clearances of more than 4 m require no correction to the design parameters.

8. Where it cannot be used

• Clause 6.1 (EN p.33): the storage of goods not covered by the design tables, for example flammable liquids, aerosols and single pallet loads of such goods, shall not be protected in accordance with this document; instead EN 12845 applies where applicable.
• Clause 6.2 (EN p.33): CMSA protection shall not be applied to FH3 to FH5 occupancies.
• Clause 4 (EN p.6): open-top containers shall not be used in storage hazards protected by CMSA unless specifically stated otherwise.

Field note: The flexibility of CMSA comes from its ability to work in a dry system; its rigidity comes from the fact that every row is tied to a specific combination of commodity, storage type, storage height and ceiling height. If there is no row in the table, no row can be produced by interpolation.

Frequently Asked Questions

What is a CMSA sprinkler and which standard governs its selection?

TS EN 12845-2:2025 Introduction, EN p.4: CMSA sprinklers operate in control mode, that is, they are capable of limiting the heat release rate of fires in storage risks, and they are used in specific challenging high hazard storage scenarios where alternative approaches are not considered suitable. Clause 5.1.1, EN p.7: CMSA pendent, dry pendent or upright sprinklers conforming to prEN 12259-15 shall be used; in dry CMSA systems only dry pendent and upright sprinklers are used.

What are the CMSA sprinkler spacings and coverage areas?

Clause 5.1.3.3, EN p.8: the minimum distance between two sprinklers is 2.4 m; the maximum spacing between two adjacent sprinklers is 3.7 m, and 3.1 m with combustible obstructed construction. The distance to a wall shall not exceed 50% of the maximum permitted spacing. The maximum area per sprinkler is 12 m² in the STC1 cases where the ceiling is unobstructed and non-combustible, obstructed and non-combustible, or unobstructed and combustible, and 9.3 m² in all other cases; the minimum area is 7.5 m².

Which sprinklers and temperature rating are used in dry CMSA systems?

Clause 6.7.2, EN p.55: upright, standard response ceiling level CMSA sprinklers with a nominal temperature rating of 141 °C shall be used in a dead-end dry pipe (tree type) or similar system; gridded or looped systems shall not be used. Clause 6.7.1, EN p.48: in dry CMSA designs the water delivery time shall be 40 s with 4 sprinklers operating, unless otherwise stated in the design tables.

How are in-rack sprinklers designed with CMSA?

Tables 17, 19 and 20, footnote a (EN p.51, 53, 54): one level of in-rack sprinklers is added at the first level above the mid-level of the rack, and that level is designed for 8 sprinklers at 115 l/min.

Which commodities cannot be protected with CMSA?

Clause 6.1, EN p.33: the storage of goods not covered by the design tables, for example flammable liquids, aerosols and single pallet loads of such goods, shall not be protected in accordance with this document; instead EN 12845 shall be applied where applicable. Clause 6.2, EN p.33: CMSA protection shall not be applied to FH3 to FH5 occupancies.

References

• TS EN 12845-2:2025 (EN 12845-2:2024), Introduction - definition of CMSA (EN p.4)
• TS EN 12845-2:2025, Clause 4 General (EN p.6)
• TS EN 12845-2:2025, Clause 5.1.1 Sprinkler type and NOTE 2 (EN p.7-8)
• TS EN 12845-2:2025, Clauses 5.1.3.3 and 5.1.3.4 (EN p.8)
• TS EN 12845-2:2025, Clause 5.1.3.5.2 and Table 2 (EN p.9-10)
• TS EN 12845-2:2025, Clause 5.1.3.5.4 (EN p.11-12)
• TS EN 12845-2:2025, Clauses 5.1.3.7 and 5.2.1 (EN p.12)
• TS EN 12845-2:2025, Clause 5.2.4 (EN p.16), 5.2.6.1 (EN p.18), 5.2.6.2 (EN p.20)
• TS EN 12845-2:2025, Clause 5.3.1 (EN p.21) and Tables 3, 4, 5 (EN p.23, 24, 26)
• 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 6.7.1 (EN p.48)
• TS EN 12845-2:2025, Table 15 (EN p.49), Table 16 (EN p.50), Table 17 (EN p.51), Table 18 (EN p.52), Table 19 (EN p.53), Table 20 (EN p.54), Table 21 (EN p.55)
• TS EN 12845-2:2025, Clause 6.7.2 (EN p.55-56) and 6.7.3 (EN p.56)
• TS EN 12845-2:2025, Tables 22 and 23 (EN p.57), Tables 24 and 25 (EN p.58)

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