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": you place at least 30 °C above the maximum ambient. A 57 °C orange bulb is not permitted in a space reaching 35 °C in summer; 68 °C is borderline and 79 °C yellow is safe.
• "Close to": but do not go higher than necessary. It lengthens response time, the sprinkler opens late in the early stage of a small fire and the fire spreads. The standard does not impose a number here; it leaves it to the engineer.

The clause goes on to permit 93 °C or 100 °C under unventilated concealed ceiling voids, skylights and glazed roofs. Near drying ovens, heaters and radiant equipment it requires special consideration — that is, specific measurement or calculation. 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, misreading is inevitable; 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	68 – 79	Red / Yellow
Steel-roofed warehouse, summer roof void	55 – 65	93	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	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, and the only sensible choice is a 93 °C green bulb. Fit 68 °C red and the system discharges with no fire; the insurer may then decline the claim as an incorrect specification. Measuring this before design starts is the designer's structural responsibility.

Dry installations: why the rating goes up

In a dry pipe system, once a sprinkler opens the valve trips, air vents and water arrives — a delay which by calculation can run to 60 seconds. The fire keeps spreading meanwhile. The same fire receives water in 5–10 seconds on a wet system.

The standard handles this on the sensitivity side, but field practice has a reflex on the temperature side too: one step up on a dry installation. Where 68 °C suits a wet system, 79 °C or 93 °C is preferred on a dry one. The logic: the dry main already has a delay, and a very sensitive bulb on top of that creates a risk of early activation from a neighbouring fire — and once one has operated, drying and re-commissioning the main takes time.

Glass bulb versus fusible link

• Glass bulb: the liquid inside expands and the bulb shatters. Manufacturing tolerance is tight and response consistent. Low RTI models fall into the quick response class. This is standard practice for EN 12259-1 certified products.
• Fusible link: two metal parts joined by solder; when the solder melts they separate and the deflector drops. More robust and resistant to mechanical impact, but response is somewhat slower and more scattered. Preferred in heavy industrial plant and in the high temperature ranges (227 °C and above).

The standard accepts both; the choice follows the fire scenario and the mechanical risk. A kitchen hood sprinkler is usually fusible link; a standard response glass bulb suits a data hall cold aisle.

A field error: mixing colours on one project

The second typical error: adding sprinklers of a different rating to an existing main during a refurbishment or extension. A hotel's main block is on 68 °C red; the contractor fitted 93 °C green in a new terrace restaurant — sound logic, since summer temperatures on a terrace are high. But the feed runs off the same manifolds, and mixing ratings and RTIs upsets the hydraulic design; the nearest red opens first while the green waits, or in the reverse scenario the wrong wing draws water while the fire is elsewhere.

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: it is the same sprinkler. Most manufacturers carry both UL/FM and EN 12259-1 listings on one model, and the colour codes are almost identical: 57 orange, 68 red, 79 yellow, 93/100 green, 141 blue, 182 mauve, 227 black. The physical product is common to both.

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 references TS EN 12845 (and where required NFPA 13) for sprinkler systems. It gives no separate table for temperature rating; the EN 12845 clause and colour table apply directly. If an inconsistency between sprinkler colours and space temperature is found during building control or fire brigade approval, it is written up and system approval is withheld.

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 °C preferred under a steel roof in high-bay storage?

Roof void temperature reaches 55–65 °C on a summer afternoon; 68 °C does not give the 30 °C margin, so a 93 °C green bulb stays on the safe side. Otherwise a heat wave produces false trips and discharges the whole water charge.

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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