False Positive Fire Test Results in Building Materials and Systems

Fire safety is a fundamental aspect of building design and construction, ensuring the protection of lives and property. A significant challenge arises if fire testing laboratories misinterpret or misapply fire test standards, leading to false positive results. These false positives occur when materials or products are incorrectly reported as meeting the sample requirements of the fire test procedure when, in reality, they don’t, leading to inappropriate, unintentional, and unrepresentative performance. This issue is particularly critical when testing materials to assess their reaction-to-fire performance and fire hazard properties, as it can compromise the safety of occupants, firefighters, and buildings, exposing the public to unnecessary and avoidable risks, with the esoteric nature of the test outcomes (indices, for example) making comparison or understanding of performance difficult. This article explores the problem of false positive fire test results, its root causes, real-world consequences, and potential solutions, with a focus on materials’ fire hazard properties and reaction-to-fire test standards such as AS/NZS 3837, AS 1530.1, AS 1530.2, AS 1530.3, AS 5637.1, AS ISO 9705, and ISO 5660-1, as of 14/06/2025.

That’s not to say the inappropriate application of AS 1530.4 for determining fire resistance performance isn’t equally concerning. Assigning a Fire Resistance Level (FRL) to a wall, fire damper, or fire door element when it is not tested in full scale, for example, can significantly overestimate its performance. The wide range of possible FRL outcomes based on specimen configuration and test conduction deserves separate study.

Problem Definition: Understanding False Positives in Fire Testing

False positives in fire testing happen when a material or product is inappropriately tested and reported to achieve a certain performance, but in reality, it does not perform at that level.

In the context of fire hazard properties, this can happen when laboratories test materials that are identified as inappropriate in standards or when they fail to account for the specific limitations of those standards. For instance, standards like AS/NZS 3837, which is used to test heat and smoke release rates for materials and products using an oxygen consumption calorimeter, can be used to predict group number performance but have clear exclusions. AS/NZS 3837 identifies itself as inappropriate for assemblies, including those with profiled faces or multilayered configurations, because it does not accurately capture such configurations. Similarly, materials that melt or shrink away, those that expand (such as intumescent) under radiant heat, or those that have reflective surfaces are identified as unsuitable for predictive testing under this standard. These caveats are further elucidated in the classification standard AS 5637.1.

Root Causes: Why False Positives Occur

The root causes of false positive fire test results often stem from a lack of understanding of fire test standards and their limitations or the classification standards that nominate them. Standards such as AS/NZS 3837, AS 1530.2, and ISO 5660-1 are designed for specific materials and configurations, yet it is common that these intentions (and related restrictions) are overlooked. If laboratories do not recognise these limitations, they may misapply the standards, leading to inaccurate or inappropriate test results.

Another cause of false positives is only following minimum procedural requirements, such as a lack of or insufficient visual observations in reporting. While standards like AS/NZS 3837 require recording Heat Release Rate (HRR) and mass loss, a lab might record a very low HRR and deem the material "Group 1" but fail to note in the report that the material rapidly melted, dripped away, or completely sublimated during the test. A bare minimum report that doesn’t include this crucial observation may lead to a false positive, as there wasn’t a chance for such observations to be reviewed and further analysed or cross-checked with the standard before issuing the final report.

Another consideration is that, while not required by the standard, including pre- and post-test photos in the final report can improve transparency and support verification of material behaviour, edge configuration, test conditions, and results. These additions help reduce the risk of misinterpretation, especially where oversight is not perceived.

Real-World Consequences: Impacts on Safety and Industry

The consequences of false positive fire test results can be severe. When buildings are constructed with materials that are incorrectly reported as achieving a certain performance that meets the requirements of the building code, they may not perform as expected during a fire, leading to multiple negative outcomes:

Rapid Fire Spread: Materials that are incorrectly reported to have a low HRR (and a better predictive group number) can allow fires to spread more quickly, engulfing entire compartments or open areas. This can exacerbate fire incidents, making containment more difficult. Increased Danger to Firefighters: Firefighters may enter buildings expecting certain levels of fire development, only to find that the materials do not hold up as anticipated, for example, determinately impacting smoke exhaust and management systems, putting them at greater risk. This can result in injuries or fatalities among firefighting personnel.

Public Safety Risks: The rapid fire spread identified above can drastically reduce safe egress times for occupants, leading to less time to evacuate and impacting the overall fire safety plan of the building. This can potentially lead to higher casualty rates in fire incidents due to crowding or overutilisation of egress paths, as concurrent areas or levels become untenable faster than anticipated or designed for. This can be compounded in schools, hospitals, and aged care facilities where occupants’ characteristics typically mandate a lower risk threshold. Economic Losses: The cost of rectification or rebuilding structures damaged by fire can be significant, not to mention the potential loss of business and disruption to communities. Legal disputes may also arise, further impacting the construction and housing industries and eroding confidence in the sector.

Reputation Damage: A critical and often overlooked repercussion is the erosion of trust in testing laboratories, the standards themselves (especially when misapplication is either unclear or ignored), and the deemed to satisfy (DTS) provisions of the National Construction Code (NCC). When false positives are uncovered—whether through fire incidents, audits, redevelopment work, due diligence before purchase of a building, ongoing project work, or post-construction testing—stakeholders, including architects, engineers, building surveyors, and regulators, lose confidence in the certifications provided by accredited laboratories.

Legal Liability: Laboratories that certify incorrect fire performance may face legal liability if their test results contribute to fire incidents. This issue is particularly concerning given the complexity of fire test standards and the potential for misinterpretation, which can undermine the reliability of certifications. Also, unlike performance solutions that apply to a singular building, a test outcome applies to a product, and as such, the potential scope of a recall could be immense, hundreds of thousands of square metres of products across hundreds of buildings. While specific documented fire incidents directly attributed to materials with false positive test results may be difficult to identify due to the relatively small frequency of major fire incidents, the potential for these materials and products to exacerbate is a serious concern. For example, if materials tested under AS/NZS 3837 are used to evaluate configurations not intended by the standard, they are likely to perform worse when tested to AS ISO 9705, which is the appropriate test procedure for such products, and thus result in worse fire performance. This underscores the need for vigilance in applying fire test standards and procedures correctly.

Identifying False Positives in Fire Test Reports

The prevalence of false positive test results has created a need to scrutinise any report or test submitted for review for code compliance or further product development purposes. This could require a detailed analysis, but on first pass—and using AS 5637.1 as an example—if the product in question does not fall under the ‘Suitable materials’ banner outlined in Clause 5.3.3, it’s a safe bet it deserves further testing. Using the example above, with a material that shrinks during testing to AS/NZS 3837, a false positive can often be identified if the recorded HRR is unusually low and flat. This is an unexpected outcome because when a material shrinks or melts, no material remains directly exposed to radiant heat, meaning the test apparatus records little or no heat release. In these cases, a failure to ignite should not be seen as a positive result. There may simply be no material left to ignite.

Additionally, when a material is classified as Group 1 under AS 5637.1 based on AS/NZS 3837 results, it should prompt a review of the testing method chosen by the laboratory. Group 1 products are permitted in occupant-sensitive and critical areas of a building, where incorrect fire performance can have serious consequences. This ensures that all requirements of AS 5637.1, being the regulatory requirements under A5G6 of the NCC, have been appropriately considered.

Potential Solutions: Addressing the Issue

To address the issue of false positive fire test results, several solutions can be implemented, as informed by industry best practices and research:

• Enhanced training: Laboratory technicians should receive comprehensive training on the interpretation and application of fire test standards that are conservative and up to date. This includes understanding the exclusions and limitations of each standard, such as those outlined in AS/NZS 3837 and ISO 5660-1.
• Mandatory verification steps: Laboratories should be required to perform additional verification steps beyond the baseline test requirements.
• Results Validation: If in doubt, request the use of a more robust test method, such as AS ISO 9705, to validate the results.
• Proficiency testing: While accreditation bodies like NATA require periodic proficiency testing, a lab might just meet this infrequent requirement without continuous internal cross-checks.
• Enhance technical auditor pool and frequency: A small pool of technical auditors and infrequent audits (e.g., every three years) can leave ample opportunity for issues to go uncorrected.
• Managing test uncertainty: If uncertain, the laboratory can choose not to provide a classification for regulatory compliance and instead report only the recorded outcomes of the test, nominating this clearly as instructed in AS/NZS 3837 and AS 5637.1.
• Best practices sharing: Jurisdictions or laboratories that have successfully addressed these issues should share their best practices with the broader industry.

Conclusion

False positive fire test results are a significant concern in ensuring the safety and reliability of building materials. These errors—where materials are incorrectly deemed compliant with fire test standards—can have severe real-world consequences, including rapid fire spread, increased risk to firefighters, public safety threats, and economic losses. The root causes of false positives often lie in the misapplication of fire test standards or a lack of understanding of material behaviours and limitations. Addressing these issues requires a comprehensive approach, including better training for laboratory technicians, enhanced verification steps, and rigorous validation of results. Laboratories must adopt a more cautious and thorough approach to testing and reporting. By implementing these solutions, the risk of false positive results can be minimised, and the integrity of fire test standards can be preserved. This proactive approach will ultimately safeguard public safety, improve industry confidence, and ensure that buildings are constructed in compliance with the building code.