EN 12845-1 Annex N: Normative Annex for CMSA Sprinklers

Source: TS EN 12845+A2:2026, Annex N (normative) "Control Mode Specific Application Sprinklers: CMSA", EN p.162.

This article is short because the source is short as well. In the standard, Annex N consists of two subclauses and three sentences in total. The annex is not a design annex, it is a referral annex.

The full text of Annex N

N.1 General (EN p.162): "For CMSA sprinkler systems, EN 12845-2 shall be applied in connection with this document."

N.2 Class conversion (EN p.162): "Due to the different hazard classification systems, EN 12845-2:2024, Annex A shall be applied; either the conversion Table A.1 or the flow chart given in Figure A.1."

The annex contains no other provision, table, figure, product list, K-factor recommendation or water demand formula.

Annex N is normative

The status of the annex is frequently confused. In the standard the heading reads: "Annex N (normative) Control Mode Specific Application Sprinklers: CMSA" (EN p.162). It is shown as normative in the contents list too. In other words, the two provisions of Annex N are not recommendations, they are provisions to be complied with.

This is the result of a structural choice introduced by the A2 amendment: instead of writing the design rules for CMSA and ESFR into EN 12845-1, they were handed over to EN 12845-2, and only two normative gateways (Annex N and Annex P) were left inside EN 12845-1.

Class conversion: EN 12845-2 Annex A

EN 12845-2:2024 Annex A (normative) "Extract for determining the hazard classification from prEN 12845-1" (EN 12845-2, EN p.59) states the following: Figure A.1 has been taken from prEN 12845-1 and updated so as to give information about the assessment of the HHS classes; Table A.1 has been created to help convert the classes given in EN 12845:2015 into the FH classes of this document.

Table A.1: Conversion of EN 12845:2015 classes into EN 12845-2

Source: EN 12845-2:2024 Table A.1, EN p.59.

For determining the storage hazard classes (HHS), the flow chart in Figure A.1, the "fire hazard classification process for storage commodities containing plastics", is used (EN 12845-2, EN p.60).

EN 12845-2 Clause 4 (EN 12845-2, EN p.6) is binding in the same direction: "For the determination of FH and HHS, Annex A shall be applied."

What is CMSA and where are the design criteria?

The Introduction of EN 12845-2:2024 (EN 12845-2, EN p.4) defines CMSA as follows: protection using sprinklers operating in control mode, that is, sprinklers which have the capability of controlling (limiting the heat release rate) fires within storage risks. CMSA protection is used in a variety of high hazard storage scenarios where alternative approaches are not considered suitable. Designs are typically specified in terms of numbers of heads operating and required head pressures.

The place of the design criteria is EN 12845-2 Clause 6.7. Clause 6.7.1 (EN 12845-2, EN p.48): "Tables 15 to 21 provide design criteria for CMSA ceiling only protection based on storage and ceiling height. For dry CMSA design the water delivery time shall be 40 s when 4 sprinklers are operating unless otherwise indicated in the design tables."

As an example, Table 15 (EN 12845-2, EN p.49) contains rows for HHS1/HHS2 commodity in STC1 storage; the K-factors in that table take the values K160, K240, K280 and K360. Rubber tyre storage is given in Table 22 (EN 12845-2, EN p.57) with K160 and K240, and heavyweight roll paper in Table 23 (EN 12845-2, EN p.57) again with K160 and K240.

The water supply duration and the shape of the design area are in EN 12845-2 Table 6 (EN 12845-2, EN p.34): 60 min for 9, 10 and 12 sprinklers; 90 min for 15 and 16 sprinklers; 120 min for 20, 24, 25 and 30 sprinklers. NOTE 2: for roll paper storage with CMSA design the duration shall be 120 min regardless of the number of sprinklers. NOTE 3: for rubber tyre storage with CMSA design the duration shall be 180 min.

Comparison of Annex N and Annex P

Source: Annex N (EN p.162) and Annex P (EN p.164).

Topics not covered in Annex N

• A definition of CMSA, a typical commodity list, a K-factor recommendation, an activation table, spacing rules, in-rack coordination, a water demand calculation formula, certification requirements or maintenance methods. None of these appear in the annex.
• The history of the annex or its status in previous editions.
• Provisions relating to CE marking.

Field note

Field note (not from the standard, this is engineering interpretation): the brevity of Annex N means that once CMSA is chosen on a project, the design responsibility passes entirely to EN 12845-2; the habits built on the hazard class of EN 12845-1 (the density-area logic) do not apply here. For this reason, the phrase "CMSA according to Annex N" in a specification does not on its own define a design criterion.

Frequently Asked Questions

What is the full content of EN 12845-1 Annex N?

TS EN 12845+A2:2026 Annex N (EN p.162) consists of two subclauses. N.1 General: for CMSA sprinkler systems, EN 12845-2 shall be applied in connection with this document. N.2 Class conversion: due to the different hazard classification systems, EN 12845-2:2024 Annex A shall be applied; either the conversion Table A.1 or the flow chart given in Figure A.1 is used. The annex contains no other provision, table or product list.

Is Annex N normative or informative?

It is normative. On the annex title page it appears as 'Annex N (normative) Control Mode Specific Application Sprinklers: CMSA' (EN p.162) and it is shown as normative in the contents list as well.

How are EN 12845 classes converted into EN 12845-2 classes?

EN 12845-2:2024 Table A.1 (EN p.59) gives the following conversion: FH1 for LH and OH1; FH2 for OH2 and OH3; FH3 for OH4; FH4 for HHP1 and HHP2; FH5 for HHP3. For determining the storage hazard classes, the flow chart in Figure A.1 is used.

Where are the CMSA design criteria found?

In EN 12845-2:2024 Clause 6.7. Clause 6.7.1 (EN p.48): Tables 15 to 21 provide design criteria for CMSA ceiling only protection based on storage and ceiling height. For dry CMSA design the water delivery time shall be 40 s when 4 sprinklers are operating unless otherwise indicated in the design tables.

What is the difference between Annex N and Annex P?

Their structure is identical, their scope differs. Annex N (normative, EN p.162) is for CMSA. Annex P (normative, EN p.164) is for ESFR and adds the following: for the water supply of ESFR sprinkler systems, it is recommended to use three 50% pump sets in accordance with EN 17451.

References

• TS EN 12845+A2:2026 Annex N, N.1 and N.2 (EN p.162)
• TS EN 12845+A2:2026 Annex P, P.1 and P.2 (EN p.164)
• TS EN 12845-2:2024 Introduction (EN p.4)
• TS EN 12845-2:2024 Clause 4 (EN p.6)
• TS EN 12845-2:2024 Clause 6.4 and Table 6 (EN p.34)
• TS EN 12845-2:2024 Clause 6.7.1 and Table 15 (EN p.48-49)
• TS EN 12845-2:2024 Table 22 and Table 23 (EN p.57)
• TS EN 12845-2:2024 Annex A and Table A.1 (EN p.59), Figure A.1 (EN p.60)

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