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* [[Combustibility]]
* [[Combustibility]]
* [[Fire properties]]
* [[Fire testing]]
* [[Fire testing]]
* [[Flame retardant]]


== Notes ==
== Notes ==

Revision as of 05:24, 2 November 2026

Reaction to fire is the response of a material or product to a specified fire exposure. It describes how the item contributes to ignition, heat release, flame spread, smoke and sometimes toxic products. The assessment is tied to a test method and scenario rather than being an unqualified property independent of exposure.[1][2]

Reaction to fire differs from Fire resistance, which concerns a construction's ability to maintain structural adequacy, integrity and insulation during exposure. A material can contribute strongly to a fire without being part of a load-bearing assembly, while a noncombustible assembly can still fail through heat transfer or deformation.[3][4]

The assessment supports product comparison, classification and design data. It uses bench-, room- and system-scale tests to measure response and to provide inputs for models. Application to an installed product requires attention to geometry, ventilation and end use.[5][6]

Ignition and heat release

Reaction-to-fire assessment begins with whether and when a material ignites under a defined exposure. Heat flux, pilot arrangement, backing and heat losses affect that transition. A material's response therefore cannot be represented by one universal ignition temperature.[7][8]

Heat release rate describes the power produced after ignition. It is linked to mass loss and effective heat of combustion, but that relationship can change during a test. A constant heat-of-combustion value should not be assumed when decomposition and combustion mode vary.[9][5]

Effective heat of combustion is the ratio of heat release to mass loss and reflects actual burning conditions. It can differ substantially from the lower calorific value measured in a bomb calorimeter, especially for solids. Reaction-to-fire data therefore provide information that an energy inventory alone cannot supply.[5][10]

The complete time history matters. Peak heat release, early growth and long-term averages answer different questions, and their averaging periods must be reported. A single peak can obscure the exposure produced by the rest of the test.[6][11]

Flame spread and material contribution

Flame spread measures how fire moves over or alongside a material as heat produces new volatile fuel. It depends on forward heat transfer, airflow, orientation and thermal response. The same material can therefore show different spread in different installations.[12][2]

Upward spread can preheat a large region above the flame, while lateral and downward spread use different heat-transfer paths. Backing and thickness alter energy storage, and char or melting changes the surface during exposure. These factors belong in the test description.[13][14]

Combustibility identifies the ability to burn, but reaction to fire measures the resulting behaviour. A combustible material can resist ignition under one exposure and spread rapidly under another. The two concepts should not be treated as synonyms.[15][7]

Fire contribution also includes total energy and the stage at which it is released. A high peak can occur early or late, and decay can leave hot residue and smouldering. Evaluating only the initial reaction misses these later effects.[16][17]

Test methods

Fire testing supplies controlled exposure and measurement. The cone calorimeter uses a small specimen and oxygen-consumption measurement, while room tests include enclosure feedback. The method determines which physical processes are represented and which extrapolations remain necessary.[11][5]

The Single Burning Item test uses two wall panels in a corner configuration without a ceiling and provides a regulatory reaction-to-fire measurement for building products. Its result belongs to that arrangement. Installed walls, ceilings and rooms can introduce different heat feedback and ventilation.[18]

The Room corner test uses a small enclosure with a defined burner and opening and collects effluent in an exhaust system. It captures room-layer and surface feedback that open tests omit. This makes it useful when the intended application includes similar enclosure effects.[5][9]

The Large-scale facade fire test evaluates complete facade arrangements at a scale that includes joints, cavities and external flame paths. Material-level tests cannot capture all these interactions. System geometry and installation must accompany any application of the result.[19][3]

Classification

The Euroclass system provides a regulatory framework for classifying reaction-to-fire performance using defined methods and criteria. A classification must be based on the applicable test and edition, not inferred from a material's generic name or from another country's category. Regulatory context matters.[1][20]

New Zealand's C/VM2 provides another example of performance criteria tied to scenario. Its flooring requirements use critical radiant flux, with higher values indicating better performance in the commentary. The required value depends on occupancy, escape function and sprinkler protection.[20]

C/VM2 also groups materials from noncombustible or limited-combustibility products through to exposed polyurethane foams in its commentary. Those groups are specific to the 2025 second edition and its application. They are not a universal reaction-to-fire classification.[20]

A classification does not describe every property. Ignition, heat release, spread and smoke can vary independently, and an acceptable result for one criterion may be unacceptable for another. The detailed test evidence remains necessary for engineering use.[21][6]

Smoke and toxic products

Reaction-to-fire assessment can include smoke production and toxic yields. These influence visibility and inhalation hazard and vary strongly with combustion mode. A material that releases less heat may still produce hazardous smoke under fuel-rich conditions.[21][22]

Soot yield affects optical density, while carbon monoxide, hydrogen cyanide and irritants affect incapacitation and survival. Their yields should be measured under conditions that represent the intended fire stage. Early well-ventilated data can underestimate later hazard.[21][23]

Fire-retarded materials provide a further example of trade-offs. Lower combustion efficiency can reduce energy release while increasing partially oxidised products. Total mass burned and total toxic production must be evaluated together rather than assuming one improvement covers all outcomes.[10][21]

Smoke and toxicity are not always included in a classification to the same depth as heat release and spread. The report should state which were measured and which remain unassessed. This prevents a reaction-to-fire label from being mistaken for a complete life-safety evaluation.[24][18]

Data for models and design

Bench-scale data can support models of larger scenarios when the relevant mechanisms and geometry are represented. Heat-release curves, ignition criteria and material properties are useful inputs, but enclosure and installation assumptions remain part of the model. The data do not make those assumptions unnecessary.[5][6]

Room tests provide stronger evidence when enclosure feedback matters, but their ventilation and geometry must match the application. Open-burning data can instead be suitable for well-ventilated conditions with comparable fuel arrangement. Selection should follow the intended scenario.[25]

Uncertainty includes measurement bias, random error, specimen variability and model extrapolation. Calibration addresses some bias, while interlaboratory trials help quantify reproducibility. These uncertainties should be visible in design comparisons.[18]

The final assessment should identify the required outcome. Product ranking, regulatory classification and design-fire development can require different data and criteria. A test that is appropriate for one may be insufficient for another.[5][20]

Limits and common misunderstandings

Reaction to fire is not an inherent pass-fail label for every situation. It is a measured response under specified exposure and mounting conditions. Real installations can change those conditions and therefore the result.[6][2]

It is not the same as fire resistance. Reaction to fire concerns contribution to fire, while fire resistance concerns the assembly's ability to continue performing required functions. Both may be needed for a complete assessment.[3][26]

A higher-class or better-performing product in one test is not guaranteed to outperform another product in every installation. Orientation, backing, enclosure, ventilation and exposure can change the ranking. Compatibility with end use must be demonstrated.[2][6]

Finally, heat release alone does not describe all hazards. Smoke, toxicity, structural response and delayed smouldering can remain. A complete fire-safety assessment must include the relevant consequences beyond the initial material reaction.[24][17]

Evaluating evidence and applicability

A reaction-to-fire report should identify the measured quantities and their reference conditions. Heat release per exposed area, total heat release, mass loss and toxic yield have different meanings. Comparing them without matching area, time and combustion basis would produce an invalid ranking.[5][11]

The fire stage should also be explicit. Early well-ventilated burning, developed fuel-rich burning and smouldering can produce different heat and product curves. A single value from one stage cannot describe the whole reaction without stating how the remaining stages are treated.[21][27]

Product form should be preserved in the assessment. Layers, facings, joints and backing can change heat transfer and expose different materials over time. A result for a small homogeneous specimen may therefore not represent the installed composite product.[28][29]

Tests can be compared only after their methods are reconciled. Cone-calorimeter, Single Burning Item and room-corner arrangements use different exposures and boundaries. Agreement or disagreement should be evaluated using the same quantity, averaging interval and enclosure interpretation.[18][5]

For classification, the detailed evidence should be checked against the applicable criteria. A strong result in one property does not compensate automatically for another criterion that was not measured or was unacceptable. This is particularly relevant when smoke and toxicity are outside the main classification.[20][24]

For design, the required scenario should control data selection. A study of early detection may need early heat-release and smoke curves, while a structural study needs developed exposure and decay. The same reaction-to-fire dataset may not support both without additional information.[30][31]

Uncertainty should be propagated into any extrapolation. Instrument error, specimen variability, enclosure differences and model assumptions all affect the final result. Sensitivity analysis can show which of these must be resolved before the reaction-to-fire evidence is reliable enough for the decision.[18][32]

A final review should distinguish observed response from modelled prediction. Observed data describe the test, while a predicted installed reaction includes additional assumptions about the building and fire. Keeping those categories separate prevents a calculated outcome from being misreported as a test result.[5][6]

A final check is whether the assessment answers the intended question. A material's ability to ignite is different from its heat release after ignition, and both differ from its smoke production or its effect on a structure. Selecting only the easiest measurement can leave the governing consequence unexamined.[5][24]

Reaction-to-fire evidence should also be separated from design-fire assumptions. A measured curve comes from a test, while a design curve is selected for analysis. The design curve may be based on test evidence, but it still includes choices about growth, developed burning and decay.[33][6]

For escape and tenability, the material response must be converted into conditions at the person. Source heat and product yields are transported and diluted before becoming exposure, and exposure time then affects incapacitation. A reaction-to-fire label alone cannot perform that conversion.[24][27]

The conversion also needs the person's location and exposure duration. A source yield can be high without producing the same concentration elsewhere, and a short high exposure can have a different effect from a long low one. Reaction-to-fire data therefore support, but do not replace, a building exposure assessment.[22][34]

For structural evaluation, the response must instead be converted into member temperature and mechanical response. Fire resistance depends on protection, loading and end conditions as well as material contribution. Reaction-to-fire and fire-resistance evidence therefore complement rather than replace each other.[26][3]

A final report should identify these boundaries and any criteria not assessed. It should state whether the result is a measurement, a classification or a modelled prediction and under which conditions each applies. That clarity prevents a reaction-to-fire result from being used as a universal safety label.[5][6]

Assembly context determines which material properties and failure modes are relevant. Kodur and Harmathy distinguish load-bearing and insulating roles, while noting that most construction materials are heterogeneous. Their composition, microstructure and moisture can change the response even when two products share a generic material name.[29]

The evidence chain should remain traceable from specimen to building. It records the tested material, its microstructure and mounting, the measured response and the conversion used for the installed condition. This allows another reviewer to see whether a result reflects material behaviour, assembly behaviour or an additional modelling assumption.[29][5]

For readers, that means a reaction-to-fire result should not be shortened into a universal label. It is evidence about a material or product under specified exposure, with separate questions still to answer about transport, occupants and structural performance. Retaining those distinctions makes the result both clearer and more useful for design. It also makes clear which questions remain outside the original test and which additional evidence is needed to answer them in the intended building and for its occupants.[24][3]

See also

Notes

  1. ↑ 1.0 1.1 Janssens (2002), pp. 3-38–3-39.
  2. ↑ 2.0 2.1 2.2 2.3 Quintiere (2002), p. 2-247.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Ministry of Business, Innovation and Employment (2025), p. 64.
  4. ↑ Kodur and Harmathy (2002), p. 1-155.
  5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 5.12 Janssens (2002), p. 3-39.
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 Babrauskas (2002), p. 3-3.
  7. ↑ 7.0 7.1 Kanury (2002), pp. 2-231–2-232.
  8. ↑ Australian Building Codes Board et al. (2005), p. 3.3-3.
  9. ↑ 9.0 9.1 Babrauskas (2002), p. 3-1.
  10. ↑ 10.0 10.1 Drysdale (2002), p. 1-95.
  11. ↑ 11.0 11.1 11.2 Janssens (2002), p. 3-56.
  12. ↑ Quintiere (2002), p. 2-246.
  13. ↑ Van Rossum (2027), §4.3.
  14. ↑ Quintiere (2002), p. 2-249.
  15. ↑ Kodur and Harmathy (2002), p. 1-157.
  16. ↑ Van Rossum (2027), §4.11.
  17. ↑ 17.0 17.1 Ohlemiller (2002), p. 2-206.
  18. ↑ 18.0 18.1 18.2 18.3 18.4 Babrauskas (2002), p. 3-33.
  19. ↑ Australian Building Codes Board et al. (2005), p. 1.6-7.
  20. ↑ 20.0 20.1 20.2 20.3 20.4 Ministry of Business, Innovation and Employment (2025), p. 52.
  21. ↑ 21.0 21.1 21.2 21.3 21.4 Purser (2002), p. 2-96.
  22. ↑ 22.0 22.1 Gottuk and Lattimer (2002), p. 2-54.
  23. ↑ Mulholland (2002), p. 2-259.
  24. ↑ 24.0 24.1 24.2 24.3 24.4 24.5 Purser (2002), pp. 2-85–2-86.
  25. ↑ Babrauskas (2002), p. 3-2.
  26. ↑ 26.0 26.1 Milke (2002), p. 4-209.
  27. ↑ 27.0 27.1 Gottuk and Lattimer (2002), p. 2-55.
  28. ↑ Beyler and Hirschler (2002), p. 1-112.
  29. ↑ 29.0 29.1 29.2 Kodur and Harmathy (2002), p. 1-156.
  30. ↑ Australian Building Codes Board et al. (2005), p. 2.5-2.
  31. ↑ Lie (2002), pp. 4-201–4-203.
  32. ↑ Van Rossum (2027), §1.7.
  33. ↑ Australian Building Codes Board et al. (2005), pp. 1.2-29–1.2-30.
  34. ↑ Purser (2002), p. 2-88.

References

  • Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). International fire engineering guidelines (2005 ed.). Australian Building Codes Board.
  • Babrauskas, V. (2002). Heat release rates. In P. J. DiNenno (Ed.), SFPE handbook of fire protection engineering (3rd ed.). National Fire Protection Association.
  • Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), SFPE handbook of fire protection engineering (3rd ed.). National Fire Protection Association.
  • Gottuk, D. T., & Lattimer, B. Y. (2002). Effect of combustion conditions on species production. In P. J. DiNenno (Ed.), SFPE handbook of fire protection engineering (3rd ed.). National Fire Protection Association.
  • Janssens, M. (2002). Calorimetry. In P. J. DiNenno (Ed.), SFPE handbook of fire protection engineering (3rd ed.). National Fire Protection Association.
  • Kanury, A. M. (2002). Flaming ignition of solid fuels. In P. J. DiNenno (Ed.), SFPE handbook of fire protection engineering (3rd ed.). National Fire Protection Association.
  • Kodur, V. K. R., & Harmathy, T. Z. (2002). Properties of building materials. In P. J. DiNenno (Ed.), SFPE handbook of fire protection engineering (3rd ed.). National Fire Protection Association.
  • Milke, J. A. (2002). Analytical methods for determining fire resistance of steel members. In P. J. DiNenno (Ed.), SFPE handbook of fire protection engineering (3rd ed.). National Fire Protection Association.
  • Ministry of Business, Innovation and Employment. (2025). C protection from fire: Verification method C/VM2 (2nd ed.). New Zealand Government.
  • Mulholland, G. W. (2002). Smoke production and properties. In P. J. DiNenno (Ed.), SFPE handbook of fire protection engineering (3rd ed.). National Fire Protection Association.
  • Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno (Ed.), SFPE handbook of fire protection engineering (3rd ed.). National Fire Protection Association.
  • Purser, D. A. (2002). Toxicity assessment of combustion products. In P. J. DiNenno (Ed.), SFPE handbook of fire protection engineering (3rd ed.). National Fire Protection Association.
  • Quintiere, J. G. (2002). Surface flame spread. In P. J. DiNenno (Ed.), SFPE handbook of fire protection engineering (3rd ed.). National Fire Protection Association.
  • Van Rossum, E. (2027). Introduction to Fire Safety Engineering. Fire Safety Academy.
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