EN 12845 Ceiling Sprinklers: Ceiling/Flush, Recessed, Concealed

Sprinkler types set into a suspended ceiling are governed in three places in TS EN 12845+A2:2026: the definitions in Clause 3 (TS p.23-24 / EN p.20-21), the limits of use in Clause 14.2 (TS p.107 / EN p.104) and the positioning rules in Clause 12.4 (TS p.75 / EN p.72). This article brings the three parts together and also lists explicitly the provisions the standard does not give for these types.

The definitions in the standard

The difference between the definitions turns on a single point: the position of the heat sensitive element relative to the plane of the ceiling. In the ceiling/flush type the element is below the plane of the ceiling; in the recessed type all or part of the element is above the plane of the ceiling; and a concealed sprinkler is a recessed sprinkler with a cover plate.

Clause 14.2.2: Restrictions on use

Clause 14.2.2 of TS EN 12845+A2:2026 (TS p.107 / EN p.104) sets up a prohibition in two layers.

First layer, for all recessed patterns: Ceiling, flush, recessed and concealed sprinklers shall not be installed in OH4, HHP or HHS areas.

Second layer, for sprinklers without fixed deflectors: Sprinklers without fixed deflectors, e.g. with retracted deflectors which drop to the operating position on actuation, shall not be fitted in the following situations:

• a) where the ceiling is more than 45° from the horizontal;
• b) where the atmosphere is corrosive or likely to have a high dust content;
• c) in racks or under shelves.

For comparison, the limits on the other patterns (TS p.107 / EN p.104): 14.2.3 prohibits sidewall sprinklers in HH installations (except for the protection of corridors, cable ducts and columns), in OH storage areas and above suspended ceilings; they might only be installed under flat ceilings. 14.2.4 requires flat spray sprinklers to be used only in concealed spaces, above suspended open ceilings and in racks.

Table 37a: Which K-factor for which type

Clause 14.2.1 (TS p.107 / EN p.104): Sprinklers shall be used for the various hazard classes in accordance with Table 37a, and as specified in 14.2.2 to 14.2.4.

The ceiling, flush, recessed and concealed types do not appear at all in the HHP/HHS rows of the table, which is consistent with the prohibition in 14.2.2.

From K-factor to pressure

Clause 14.3 (TS p.107-108 / EN p.104-105): The water flow from a sprinkler shall be calculated from the formula Q = K√P, where Q is the flow in litres per minute, K is the constant given in Table 37a and P is the pressure in bar.

Inverted, the formula becomes P = (Q/K)². Example: in an OH class with a design density of 5.0 mm/min and an area of coverage per sprinkler of 12 m², the required flow is 5.0 × 12 = 60 l/min. For that flow:

Both values have to be read together with the 0.35 bar minimum that Clause 13.4.4 gives for OH (TS p.105 / EN p.102): the 0.27 bar calculated with K115 falls below that threshold, so the governing value becomes 0.35 bar, while the 0.56 bar found with K80 is above the threshold and is itself the governing value.

Clause 14.4 and Table 37b: Temperature rating and colour code

Clause 14.4 Sprinkler temperature ratings (TS p.108 / EN p.105): "Sprinklers shall be chosen with a temperature rating close to but no lower than 30 °C above the highest anticipated ambient temperature."

This sentence sets a lower limit: the nominal rating selected cannot be below the ambient temperature + 30 °C, and it is required to be close to that value. Reading it as a requirement not to exceed the ambient temperature by 30 °C turns the provision on its head.

The same clause continues: in unventilated concealed spaces, under skylights or glass roofs etc., it might be necessary to install sprinklers with a higher operating temperature, up to 93 °C or 100 °C. Special consideration shall be given to the rating of sprinklers in the vicinity of drying ovens, heaters and other equipment which gives off radiant heat.

NOTE 1: Under normal conditions in temperate climates a rating of 68 °C or 74 °C is suitable. NOTE 2: Sprinklers are colour coded in accordance with EN 12259-1 to indicate their temperature rating as specified in Table 37b.

Table 37b (TS p.108 / EN p.105)

The point to watch: there is no 74 °C row in the table. Yellow corresponds to 79 °C. The figure 74 °C appears only in NOTE 1 to Clause 14.4, as a rating suitable in a temperate climate.

Positioning: deflector distances and clear space

Clause 12.4.2 (TS p.75 / EN p.72) contains two separate rules.

Upper limits: Sprinklers shall be installed not lower than 0.3 m below the underside of combustible ceilings or 0.45 m below Euroclass A1 or A2 (or an equivalent in existing national classification systems) roofs or ceilings.

Preferred band and the exception for recessed patterns: Where possible, sprinklers shall be situated with the deflector between 0.075 m and 0.15 m below the ceiling or roof, except when ceiling, flush or recessed sprinklers are used. Where circumstances make it unavoidable to use the maximum distances of 0.3 m and 0.45 m, the area involved shall be as small as possible.

Exempting the recessed patterns from this band follows directly from the definitions: the body of a ceiling/flush or recessed sprinkler is already partly or wholly above the plane of the ceiling.

Clause 12.1.2 (TS p.73 / EN p.70) gives the clear space to be maintained below the deflector:

Clause 12.4.3 (TS p.75 / EN p.72): Sprinklers shall be installed with their deflectors parallel to the slope of the roof or ceiling. Where the slope is greater than 30° to the horizontal plane, a row of sprinklers shall be fixed at the apex or not more than 0.75 m radially from it.

Rosettes, guards and painting

Clause 14.8 Sprinkler rosettes (TS p.110 / EN p.107): Rosettes shall be made of metal or thermosetting plastic. Rosettes shall not be used to support ceilings or other structures. No part of a rosette shall project from the ceiling below the top of the visible portion of the heat sensitive element of the sprinkler.

Clause 14.6 Sprinkler guards (TS p.109 / EN p.106): When sprinklers other than ceiling or flush sprinklers are installed in a position at risk of accidental mechanical damage, they shall be fitted with a suitable metal guard. Keeping the recessed patterns outside this requirement is consistent with the fact that being set into the plane of the ceiling already lowers their exposure to damage.

Clause 14.1 General (TS p.106 / EN p.103): Only new (unused) sprinklers shall be used. Sprinklers shall not be painted except as permitted by EN 12259-1. They shall not be altered in any way after despatch from the manufacturing works, and no decoration or coating other than that specified in 14.9 shall be applied to them. NOTE: This standard covers only the types of sprinkler specified in EN 12259-1.

Clause 14.9 Corrosion protection of sprinklers (TS p.110 / EN p.107): Sprinklers installed in premises where corrosive vapours are prevalent shall be protected with a suitable corrosion resistant coating applied by the supplier in conformity with EN 12259-1, unless the sprinklers are manufactured from suitably corrosion resistant materials. The anti-corrosion treatment shall not be applied to sprinkler bulbs.

What the standard does not say here

The following do not appear in the text of TS EN 12845+A2:2026:

• A nominal release temperature for the cover plate of a concealed sprinkler (for example 57 °C) or a requirement that the cover plate be rated lower than the bulb
• A definition of "two stage activation" for a concealed cover plate
• A separate approval or certification provision for the concealed cover plate
• A requirement to order factory painted cover plates, or any statement that painting on site invalidates the approval

The only thing the standard says about painting is Clause 14.1: sprinklers shall not be painted except as permitted by EN 12259-1.

Thermal sensitivity

Clause 14.5.1 (TS p.109 / EN p.106): Sprinklers of different sensitivities shall be used in accordance with Table 38. Where sprinklers are situated in racks, the sprinklers at the ceiling shall have a sensitivity equal to or of slower response than the sprinklers situated in the racks. NOTE: Most types of sprinkler are rated, in descending order of sensitivity, as one of the following (see EN 12259-1): quick response, special response, standard response 'A'.

Field note

In areas such as offices and hotels, where the architectural priority is high, the class limit on recessed patterns (14.2.2) rarely causes difficulty; the real risk is that a store room or plant space in the same building rises to OH4 or HHS and the ceiling pattern is simply carried on into it. Showing the class boundaries area by area on the block plan (Clause 18.1 b) makes that boundary easier to follow on site. (This paragraph is engineering commentary.)

Frequently Asked Questions

Where are ceiling, flush, recessed and concealed sprinklers prohibited?

TS EN 12845+A2:2026 Clause 14.2.2 (TS p.107 / EN p.104): ceiling, flush, recessed and concealed sprinklers shall not be installed in OH4, HHP or HHS areas. In addition, sprinklers without fixed deflectors (for example types with retracted deflectors which drop to the operating position on actuation) shall not be fitted in three situations: a) where the ceiling is more than 45° from the horizontal; b) where the atmosphere is corrosive or likely to have a high dust content; c) in racks or under shelves.

How does the standard define these sprinkler types?

Clause 3.55 sprinkler, ceiling or flush: pendent sprinkler for fitting partly above, but with the temperature sensitive element located below the plane of the ceiling. 3.56 sprinkler, concealed: recessed sprinkler with a cover plate that disengages when heat is applied. 3.66 sprinkler, recessed: sprinkler in which all or part of the heat sensing element is above the lower plane of the ceiling. 3.65 sprinkler, pendant: sprinkler with the nozzle directing the water downwards. (TS p.23-24 / EN p.20-21)

How is the sprinkler temperature rating selected?

Clause 14.4 (TS p.108 / EN p.105): sprinklers shall be chosen with a temperature rating close to but no lower than 30 °C above the highest anticipated ambient temperature. In other words, ambient + 30 °C is a lower limit, not an upper limit. NOTE 1: under normal conditions in temperate climates a rating of 68 °C or 74 °C is suitable. In unventilated concealed spaces, under skylights or glass roofs, sprinklers with a higher operating temperature, up to 93 °C or 100 °C, might be necessary.

What temperature does a yellow bulb correspond to in Table 37b?

79 °C. The glass bulb series of Table 37b in TS EN 12845+A2:2026 (TS p.108 / EN p.105) is: 57 orange, 68 red, 79 yellow, 93 green, 100 green, 121 blue, 141 blue, 163 mauve, 182 mauve, 204 black, 227 black, 260 black, 286 black, 343 black. There is no 74 °C row in the table; 74 °C appears only in NOTE 1 to Clause 14.4 as a suitable rating.

How far below the ceiling should the deflector be?

Clause 12.4.2 (TS p.75 / EN p.72): where possible, sprinklers shall be situated with the deflector between 0.075 m and 0.15 m below the ceiling or roof, except when ceiling, flush or recessed sprinklers are used. The same clause also gives the upper limits: sprinklers shall be installed not lower than 0.3 m below the underside of combustible ceilings or 0.45 m below Euroclass A1 or A2 roofs or ceilings.

References

• TS EN 12845+A2:2026 Clause 3.55, 3.56, 3.57 (TS p.23 / EN p.20)
• TS EN 12845+A2:2026 Clause 3.65, 3.66, 3.67 (TS p.24 / EN p.21)
• TS EN 12845+A2:2026 Clause 12.1.2 Clear space below the deflector (TS p.73 / EN p.70)
• TS EN 12845+A2:2026 Clause 12.4.2 and 12.4.3 Position of sprinklers (TS p.75 / EN p.72)
• TS EN 12845+A2:2026 Clause 13.4.4 Minimum sprinkler discharge pressure (TS p.105 / EN p.102)
• TS EN 12845+A2:2026 Clause 14.1 General (TS p.106 / EN p.103)
• TS EN 12845+A2:2026 Clause 14.2.1, Table 37a, 14.2.2, 14.2.3, 14.2.4, 14.3 (TS p.107 / EN p.104)
• TS EN 12845+A2:2026 Clause 14.4, Table 37b (TS p.108 / EN p.105)
• TS EN 12845+A2:2026 Clause 14.5.1, Table 38, 14.6, 14.7 (TS p.109 / EN p.106)
• TS EN 12845+A2:2026 Clause 14.8 Rosettes, 14.9 Corrosion protection (TS p.110 / EN p.107)
• TS EN 12845+A2:2026 Clause 18.1 Block plan (TS p.118 / EN p.115)

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