Euroclass system

The Euroclass system is the European system for classifying building products by their reaction to fire, which describes how much a product contributes to the hazard of a growing fire. Its tests include the Single Burning Item test (SBI), a European regulatory heat release rate test for building products in which two wall panels form a corner without a ceiling. The system grew out of European research on how small-scale test results can predict the behaviour of wall and ceiling linings in a full-scale room fire.

Classification systems of this kind sort products into a small number of performance groups. Building regulations can then require a better group in places where a fast-growing fire would be most dangerous, such as escape routes. The quantity that matters most is the heat release rate, because it governs both the growth of the fire and the production of smoke and toxic gases. The Euroclass system is one of several such systems. New Zealand, for example, uses Group Numbers based on the time to flashover in a full-scale room test. Its verification method C/VM2 listed BS EN 13501 among the product standards it referred to, until the second edition of 2025 moved such references to separate specifications.

Reaction to fire and the need for classes

The heat release rate is the main variable that determines how much a material adds to the hazard of a fire in a room. It is directly related to the rate at which the material loses mass. The release of toxic gases equals this mass loss rate multiplied by the yield of each gas. A material with a high yield of toxic gases can therefore be less hazardous than one with a low yield if it burns much more slowly. Many fire retardant treatments, for example, raise the yield of toxic gases but greatly reduce the mass loss rate, and so lower the overall hazard.

There are two basic ways to judge the fire hazard of a material. The first is a set of full-scale fire tests covering all relevant conditions of fire and end use. The second is to measure the heat release rate on a small sample and use a calculation to estimate the full-scale performance. The SFPE Handbook calls the second approach more versatile, quicker and cheaper, and notes that it has become the preferred approach. Classification systems usually combine both: a full-scale test defines what good and poor performance mean, and smaller tests are used to place products in the right class.

Older national fire testing methods for reaction to fire often included only a crude measure of the heat release rate. According to the SFPE Handbook, most of these methods were developed decades ago, their measuring techniques are inaccurate and obsolete, and their exposure conditions were poorly defined. Their results are therefore hard to relate to real fire performance. Most current heat release rate measurements use oxygen consumption calorimetry, with a standard value of 13.1 MJ released per kilogram of oxygen consumed.

European research behind the system

The basis of the European approach was laid in the Nordic countries. The international room test standard ISO 9705, published in 1992, is based mainly on Nordic research. In this test, a product lines the walls and ceiling of a small room of 2.44 m by 3.67 m and 2.44 m high, with a door of 0.76 m by 2 m. A gas burner of 0.17 m by 0.17 m stands in a corner and delivers 100 kW for 10 minutes, followed by 300 kW for another 10 minutes. The room-corner arrangement was developed as a realistic test for the flame spread behaviour of interior finish materials.

The ISO 9705 room corner test, the full-scale reference for classifying wall and ceiling linings: burner of 100 kW and then 300 kW in a corner of a lined room. Based on Gottuk and Lattimer (2002), p. 2-67, and Janssens (2002), p. 3-58.

In 1987, Wickström and Göransson published a model that predicts the heat release rate in this room from small-scale cone calorimeter data. The model was later extended and validated in the European research programme EUREFIC, short for European Reaction to Fire Classification. Its main purpose was to predict the performance category a product would reach in the ISO 9705 test, using only bench-scale data. The SFPE Handbook describes it as an unquestionable success for that purpose. EUREFIC was intended to raise the technical level of evaluating surface linings in the Nordic countries in the early 1990s.

The model has clear limits. It applies only to the standard ISO 9705 room with its standard doorway and burner programme. It requires the same material on walls and ceiling, and it cannot deal with products that do not ignite in the cone calorimeter at an irradiance of 25 kW/m². The handbook therefore calls it a major breakthrough, but not the final answer for modelling wall and ceiling products.

The Single Burning Item test

The SBI test is a European regulatory heat release rate test for building products. Two wall panels of the product are mounted in a corner, without a ceiling. Like other heat release rate apparatuses, it has been tested in round robins to quantify the random error that can be expected. A few substances release a heat per kilogram of oxygen that differs substantially from the standard value of 13.1 MJ/kg, and for these a correction can be made if their composition is known.

The precision of such tests is measured in round robins, in which several laboratories test the same products. The trials were held in different years and with different numbers of laboratories. The SFPE Handbook compares the results for four apparatuses:

Repeatability (r) and reproducibility (R) of the peak heat release rate in round robins of four test apparatuses, as 95 per cent limits. Based on Babrauskas (2002b), p. 3-33.

Apparatus	Year	Laboratories	Peak HRR, r (%)	Peak HRR, R (%)	Total HR, r (%)	Total HR, R (%)
Cone calorimeter	2000	4	17	23	8	15
ICAL	1999	3	56	67	72	118
SBI	1997	16	38	54	47	71
Room calorimeter	1994	12	65	79	25	41

In this table, r is the repeatability within one laboratory and R the reproducibility between laboratories, both as 95 per cent confidence limits. Dividing a value by 2.8 gives the corresponding standard deviation. For the SBI, the reproducibility of the peak heat release rate was 54 per cent, against 23 per cent for the cone calorimeter. The bench-scale cone calorimeter was the most precise apparatus in these trials, and the full-scale room calorimeter the least precise for the peak value.

Use in regulation and design

Building codes in most countries regulate the linings of rooms and other areas tightly. Some important occupancies, such as dwellings, are often not covered, and older buildings may predate the current rules. A classification is a statement about a tested product in a defined configuration. The SFPE Handbook stresses that generic data from databases must never be used to seek regulatory approval for a product; the product itself must be tested in a laboratory.

The New Zealand system shows how such classes are tied to locations in a building. Its Group Numbers run from 1 (best) to 4 (worst) and are based on the time to flashover in the ISO 9705 test, with flashover taken as a heat release rate of 1.0 MW. Group Number 1 materials, such as plasterboard, reach no flashover in 20 minutes. Group 2 materials, such as many fire retardant treated timbers, reach none in 10 minutes. Group 3 materials, such as ordinary timber, reach none in 2 minutes, and Group 4 materials, such as exposed polyurethane foam, reach flashover within 2 minutes. Group 4 materials are not acceptable in occupied spaces.

Classification by time to flashover in the ISO 9705 room test, as used for the New Zealand Group Numbers 1 to 4. Based on Ministry of Business, Innovation and Employment (2013), p. 141.

The New Zealand rules also add a smoke criterion. A suffix "S" means that the average smoke production must stay below 5.0 m²/s in the ISO 9705 test, or below 250 m²/kg in the cone calorimeter. The 5.0 m²/s value comes from a proposal by Sundström in the EUREFIC project. New Zealand Building Code clause C3.4 is reproduced in the 2013 commentary. Under it, wall and ceiling linings in exitways of unsprinklered buildings had to meet Group Number 1-S, while Group 1 or 2 was enough in sprinklered buildings. Materials classified as non-combustible in the ISO 1182 test can be given Group Number 1 or 1-S without further testing, which links the classes to the combustibility of the material.

Verification Method C/VM2 (second edition, 2025) moved the test specifications for surface linings to separate Building Product Specifications. In doing so, it removed its references to a list of product standards that includes BS EN 13501, BS 8414, ISO 5660 and ISO 9705. The Group Number requirements of clause C3.4 are now given in a table in the verification method itself.

Limits and common misconceptions

A class does not predict how a product will behave in every building. The smaller tests behind a classification are calibrated against one reference scenario, and the EUREFIC model, for example, is hard-wired to one room size, one burner and one mounting. Some products are not suitable for small-scale testing at all. The New Zealand commentary names metal-faced sandwich panels and foil-faced combustible insulation as examples, because the small-scale correlation does not hold for them.

A second misconception is that smoke and heat classes measure the same thing. The New Zealand commentary notes that no clear correlation has been found between the smoke measured in the full-scale room test and in the cone calorimeter, probably because of differences in scale and ventilation. It also states that the heat release rate is the most important parameter, while smoke production is secondary but rises with the burning rate.

A third point is that reaction-to-fire classes say nothing about how long a wall or floor can contain a fully developed fire. Reaction to fire concerns the growth of a fire, when linings and contents decide how fast it spreads and how much heat it releases. In fire resistance studies, by contrast, the growth period can be disregarded, because the risk of failure of structural members and fire separations only begins once the fire is fully developed.

See also

• Room corner test
• Cone calorimeter
• Fire resistance test
• Large-scale facade fire test

References

• Babrauskas, V. (2002b). Heat release rates. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), SFPE handbook of fire protection engineering (3rd ed., pp. 3-1–3-37). National Fire Protection Association; Society of Fire Protection Engineers.
• Gottuk, D. T., & Lattimer, B. Y. (2002). Effect of combustion conditions on species production. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), SFPE handbook of fire protection engineering (3rd ed., pp. 2-54–2-82). National Fire Protection Association; Society of Fire Protection Engineers.
• Hall, J. R., Jr. (2002b). Product fire risk. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), SFPE handbook of fire protection engineering (3rd ed., pp. 5-143–5-152). National Fire Protection Association; Society of Fire Protection Engineers.
• Janssens, M. (2002). Calorimetry. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), SFPE handbook of fire protection engineering (3rd ed., pp. 3-38–3-62). National Fire Protection Association; Society of Fire Protection Engineers.
• Lie, T. T. (2002). Fire temperature-time relations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), SFPE handbook of fire protection engineering (3rd ed., pp. 4-201–4-208). National Fire Protection Association; Society of Fire Protection Engineers.
• Ministry of Business, Innovation and Employment. (2013). Commentary for Building Code clauses C1–C6 and Verification Method C/VM2.
• Ministry of Business, Innovation and Employment. (2025a). Get to know C/VM2 second edition: Information on the new edition of the verification method.
• Ministry of Business, Innovation and Employment. (2025b). Verification Method C/VM2: Framework for fire safety design (2nd ed.).
• Quintiere, J. G. (2002b). Surface flame spread. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), SFPE handbook of fire protection engineering (3rd ed., pp. 2-246–2-257). National Fire Protection Association; Society of Fire Protection Engineers.