EN 12845 Sprinkler Temperature Ratings and Colour Codes

The ambient plus 30 °C margin, glass bulb and fusible link colour codes, selection logic for roof voids, boiler rooms and oven surroundings, and two lessons from site.

During commissioning week on a logistics project, three sprinklers burst in succession under the roof and soaked the racking — with no fire, only the July midday sun. On site, standard 68 °C red bulb sprinklers had been lined up under a steel trapezoidal roof. We hung a thermometer under the ceiling and read 61 °C at 14:30. The ambient plus 30 °C rule catches this error on its own; but nobody had sat down at design stage and measured the summer temperature in the upper void.

EN 12845 places temperature rating in two places: one clause gives the selection rule, and a table lists the colour codes aligned with EN 12259-1. A designer who does not read both together builds a system that is either over-cautious (slow activation) or over-aggressive (false trips). Below: the rule, the colour codes and typical field decisions in order.

The design principle: ambient plus 30 °C

The first sentence of the clause is clear: sprinklers shall be chosen with a temperature rating close to but no lower than 30 °C above the highest anticipated ambient temperature. Two parts matter:

• "No lower than 30 °C above": at least 30 °C is added to the maximum ambient. A space reaching 35 °C in summer needs at least 65 °C: a 57 °C orange bulb does not comply, while a 68 °C red bulb complies and also best meets the “close to” condition.
• "Close to": do not go higher than necessary either; a higher rating means the sprinkler opens later in the early stage of a small fire. The standard sets no numerical upper limit; it leaves the choice to the designer.

The clause goes on to say that in unventilated concealed spaces, under skylights or glass roofs it might be necessary to install sprinklers with a higher operating temperature, up to 93 °C or 100 °C. Near drying ovens, heaters and other equipment giving off radiant heat it requires special consideration of the rating, without giving a numerical method. A note adds that 68 °C or 74 °C is suitable under normal conditions in a temperate climate.

Colour codes

Reading a sprinkler's temperature rating from its colour before its label is standard field practice. The liquid inside a glass bulb is coloured; on a fusible link sprinkler the yoke arms are coloured. The standard gives two separate columns:

Glass bulb		Fusible link (yoke arms)
Nominal temperature (°C)	Liquid colour	Range (°C)	Arm colour
57	Orange	57 – 77	Uncoloured
68	Red	80 – 107	White
79	Yellow	121 – 149	Blue
93	Green	163 – 191	Red
100	Green	204 – 246	Green
121	Blue	260 – 302	Orange
141	Blue	320 – 343	Black
163	Mauve	—	—
182	Mauve	—	—
204 / 227 / 260 / 286 / 343	Black	—	—

A caution for site inspection: red can indicate two different ratings. Red in a glass bulb means 68 °C; red yoke arms on a fusible link mean 163–191 °C. Where both types are mixed in one building, the risk of misreading is high; standardising on one type is not always possible, but a labelling procedure is essential.

Typical selection by environment

The table below applies the plus 30 °C rule to field temperatures. It is a starting point for the designer; the final value must always be confirmed by measurement on site.

Space	Expected max ambient (°C)	Rating (°C)	Glass bulb colour
Office, hotel room, air-conditioned shop	30 – 35	68	Red
Unconditioned school or mall corridor	40	79	Yellow
Steel-roofed warehouse, summer roof void	55 – 65	93 – 100	Green
Under a glazed roof or atrium	60 – 70	93 – 100	Green
Boiler room, routine	50 – 60	93	Green
Boiler room, near a hot flue	90 – 110	141	Blue
Near a paint or drying oven	140 – 150	182	Mauve
Around an industrial furnace	180 – 200	227 – 260	Black

High ceilings and roof voids: where the error usually is

The warning about unventilated ceiling voids is no accident. Steel trapezoidal roofs are standard in Turkish logistics zones; where insulation is weak or there is no internal air movement, 60 °C under the roof on a summer afternoon is normal. In three separate measurements at 12 m high warehouses in the Marmara industrial belt, July roof void readings were 58 °C, 63 °C and 67 °C, with outside air at 35–37 °C.

Adding 30 °C to those puts the target at 88–97 °C: 93 °C for the first two warehouses and 100 °C for the third, measured at 67 °C (both green bulbs). In a space where the roof void exceeds 60 °C, a 68 °C red bulb sits so close to its operating temperature that it risks opening with no fire. Measuring this before design starts is the designer's responsibility.

Dry installations: the constraint is sensitivity, not temperature

In a dry pipe installation, once a sprinkler opens the dry alarm valve trips, the air in the pipework escapes and only then does water arrive. Table 18 (Clause 11.2.2) limits this delay: the maximum time between a single sprinkler opening and water discharging shall not exceed 90 s in LH and 60 s in OH and HH.

EN 12845 does not require a higher temperature rating for dry installations; the rating is chosen under Clause 14.4 for every installation type. The constraint specific to dry installations is on the sensitivity side: under Table 38 (Clause 14.5.1) quick response sprinklers shall not be used in dry and pre-action Type A installations, while standard ‘A’ and special response sprinklers may be used. Some designers choose one step higher on dry installations, but this is not a requirement of the standard.

Glass bulb and fusible link

• Glass bulb: the liquid inside expands as it heats and shatters the bulb. Quick response models are products with a low RTI (Response Time Index); the response class is determined in accordance with EN 12259-1.
• Fusible link: metal parts joined by solder; when the solder melts at the rated temperature the link separates and the sprinkler opens. Its sensitivity likewise depends on the product’s EN 12259-1 class.

The standard accepts both; Table 37b gives colour codes for both types up to 343 °C. The choice follows the fire scenario, the ambient conditions and the mechanical risk.

A field error: mixing colours on one project

The second typical error: adding sprinklers of a different rating or sensitivity to an existing installation during a refurbishment or extension. For example, choosing 93 °C green bulbs for a hot terrace restaurant later added to a hotel whose main block is on 68 °C red may be correct in itself. But where different ratings and response classes are mixed in the same area, the operating sequence changes; more sensitive sprinklers remote from the fire opening first can take the operation outside the area of operation assumed in the hydraulic calculation.

A note in the standard states this plainly: when new sprinklers are added to an existing installation, it can be necessary to take into account the effect of different sensitivities in order to avoid excessive activations. Temperature and sensitivity must be reviewed together during refurbishment; a "fit whatever is in the store" approach is risky for both insurance and product liability.

Comparison with NFPA 13

The good news: the physical product is often the same. Many manufacturers carry both UL/FM and EN 12259-1 approvals on one model, and the glass bulb colours largely overlap (NFPA 13-2025 Table 7.2.4.1(a)): 57 orange, 68 red, 79 yellow, 93 green, 121–149 blue, 163–191 purple, 204 and above black. EN 12845 Table 37b additionally lists 100 °C (green).

The difference is terminology and grouping:

• NFPA 13 names temperature ranges by group — Ordinary (57–77 °C), Intermediate (79–107 °C), High (121–149 °C), Extra High (163–191 °C), Very Extra High (204–246 °C), Ultra High (260–302 °C).
• EN 12845 works with numerical values (57, 68, 79, 93, 100, 121, 141, 163, 182, 204, 227, 260, 286, 343 °C) and uses no group names.

Do not mix the two on one project: use the terminology of whichever standard the authority having jurisdiction and the insurer are working to, consistently across labels, drawings and the handover file.

Turkish context

BYKHY Article 96(5) requires sprinkler system design to TS EN 12845, and Article 96(1) requires system components to comply with TS EN 12259. NFPA 13 can be applied only as an added layer requested by the insurer or investor, provided these minimum requirements are met. It gives no separate table for temperature rating; the EN 12845 clause and colour table apply directly.

Practical advice: at concept stage keep a one-line temperature note for each space — space, expected maximum ambient, selected rating, colour. That note becomes the first document consulted at inspection and at any future refurbishment, and gives you a ready answer to "why was 93 °C used here".

Frequently asked questions

How is a sprinkler temperature rating selected?

At least 30 °C above the highest anticipated ambient, but not higher than necessary. Typically 68 °C or 74 °C in a temperate climate; 93 °C or 100 °C under unventilated ceiling voids, skylights and glazed roofs. Near ovens and heaters, special consideration is mandatory.

What does the glass bulb colour indicate?

57 orange, 68 red, 79 yellow, 93/100 green, 121/141 blue, 163/182 mauve, 204 and above black. The rating can be read directly from the head during a site check.

Are fusible link colour codes different?

Yes. On a fusible link the colour is applied to the yoke arms and covers ranges: 57–77 uncoloured, 80–107 white, 121–149 blue, 163–191 red, 204–246 green, 260–302 orange, 320–343 black. "Red equals 68 °C" is true only for glass bulbs.

Why is 93–100 °C chosen under a steel roof in high-bay storage?

Roof void temperature can reach 55–65 °C on a summer afternoon; 68 °C does not give the 30 °C margin. Up to 63 °C ambient 93 °C is needed, above that 100 °C (both green bulbs). Otherwise hot weather creates a risk of sprinklers opening with no fire.

Do NFPA 13 and EN 12845 ratings agree?

In practice yes — the physical sprinkler is the same and the colour codes overlap. The difference is in the naming: NFPA uses group names, EN 12845 uses numerical values. Do not mix the two languages on one project.

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