This International Standard gives guidance on the evaluation and expression of uncertainty of fire test method measurements developed and maintained by ISO/TC 92, based on the approach presented in ISO/IEC Guide 98-3. Application of this International Standard is limited to tests that provide quantitative results in engineering units. This includes, for example, methods for measuring the heat release rate of burning specimens based on oxygen consumption calorimetry, as in ISO 5660-1:2002. This International Standard does not apply to tests that provide results in the form of indices or binary results (e.g. pass/fail). In some cases, additional guidance will be required to supplement this International Standard. For example, the expression and use of uncertainty at low levels may require additional guidance and uncertainties associated with sampling are not explicitly addressed. NOTE 1 The procedures described in this International Standard involve some complex mathematics. Basic concepts of measurement uncertainty are provided in Annex A. NOTE 2 The guidelines presented in this International Standard may also be used to evaluate and express the uncertainty associated with fire test results. However, it is not always possible to quantify the uncertainty of fire test results as some sources of uncertainty cannot be accounted for.