DEF STAN 02-713 Determination of Toxicity Index of Combustion Products from Small Material Samples

The standard "DEF STAN 02-713 Determination of the Toxicity Index of Combustion Products from Small Material Samples," published under British Defence Standards, describes the requirements for one of a series of test methods for determining the fire characteristics of materials referenced in DEF STAN 07-247. This test examines the toxicity of combustion products with respect to a limited number of small molecular species produced when a small sample of material burns completely under specified conditions.

This test is intended to form part of the pre-selection screening process for materials and should not be construed as an assessment of toxicity hazards under actual fire conditions. The test method is intended for the analysis of a specific group of gas species commonly found in the combustion products of materials used in military applications and which may be lethal in the event of a fire. This standard does not address acute mental retardation effects, delayed or long-term toxicity, or toxicity associated with particulate combustion products. The set of gas species analyzed is not exhaustive, and the test does not determine the total toxicity of all components of the combustion products.

Additionally, this test does not attempt to take into account the effect of a material's burning rate on its contribution to the toxicity hazard.

In principle, analytical data of specific types of small molecular gases released when the material is completely burned under specified conditions are mathematically calculated based on the exposure level (in ppm) of each gas that will lead to lethal consequences within 30 minutes, and a combined toxicity index is obtained.

For the purposes of this standard, the following terms and definitions apply:

• 1 m³Concentration per 100g (ppm): The gas concentration (ppm) produced under test conditions is scaled for 100g of material and the combustion products are expressed as 1m³It is recalculated as if it were spread over a volume of .
• Critical factor: The concentration (ppm) of a gas considered lethal to humans during a 30-minute exposure period.
• Measured concentration: The gas concentration measured in the test chamber, in ppm.
• Toxicity index: The sum of the toxicity factors of selected gases produced by the combustion of a material under the conditions specified in the test.
• Production batch: The quantity of material produced in the same campaign from the same starting materials, under the same process conditions and with the same equipment.
• Production material: Material having the same composition, produced from the same raw materials, under the same process conditions, with the same equipment and at the same location, as the material to be supplied for end use under the contract / order specifying this standard.

Small samples with a predetermined mass (usually about 1 gram) are completely burned in a closed chamber with a volume of 0,7–1,0 m³ using a Bunsen burner fed with air and gas, at a temperature of 1150 degrees plus/minus 25 degrees^.

The resulting chamber atmosphere is analyzed quantitatively for a specific group of gases. Background corrections are subtracted for the amounts of carbon monoxide, carbon dioxide, and nitrogen oxides produced by the burner.

For each gas, the measured concentration is scaled per 100 g of material and recalculated as if the combustion products were spread over a volume of exactly 1 m³ ^. The resulting concentration is expressed as a critical factor ratio, which is equal to the concentration of the gas considered lethal to humans after 30 minutes of exposure.

The toxicity index of the material is obtained by summing the rates for all detected gases.

Published by the British Ministry of Defence, this standard establishes a test method for assessing the potential toxicity of smoke and gases released when materials burn using small-scale samples. This standard is critical for ensuring the safety of materials used in military applications, where fire hazards in enclosed spaces, such as submarines, aircraft, or vehicles, can pose serious risks to personnel. By measuring toxicity, it helps select low-risk materials that minimize health effects during fires.

The DEF STAN 02-713 standard arose from the need to address fire safety in high-risk environments. Since its publication, the standard has been revised to incorporate advances in toxic gas analysis and international harmonization. This update responds to feedback from defense trials and evolving safety regulations, improving test protocols to provide better accuracy in measuring sublethal and lethal exposure levels.

This standard draws parallels with the civilian standard “ISO 13344 Estimation of lethal toxic potential of fire wastes” but is specifically designed for military-grade materials and emphasizes rapid testing of small samples to support rapid material screening.

In short, the DEF STA 02-713 standard specifies a small-scale combustion test to obtain the toxicity index , a numerical value indicating the toxic hazard potential of the material . The toxicity index is calculated based on the concentration of key toxic gases (e.g., carbon monoxide, hydrocyanic acid, and hydrochloric acid) that cause incapacitation or death within specific exposure times.

The key elements of this standard are:

• Sample preparation: Small samples of material (typically 15-50 grams) are conditioned to simulate real-world use, such as composites, textiles, or polymers.
• Test apparatus: A controlled oven or radiant panel exposes the sample to heat fluxes simulating fire conditions (e.g. 25-50 kW/m²). Combustion products are collected in a chamber and analyzed by gas chromatography or Fourier transform infrared spectroscopy (FTIR).
• Exposure simulation: The test models two scenarios to capture a variety of fire behaviors: flameless (smouldering) and flame decomposition. Rodent exposure (historically used) or computational models predict human response.
• Toxicity measures: The toxicity response is derived from the onset time (e.g., via a fractional effective dose model). Values ​​below 1,0 indicate low toxicity, while higher scores indicate high-risk materials.
• Reporting: Results include detailed gas yields, optical density for smoke, and compliance thresholds. Pass/fail criteria depend on the end use (e.g., more stringent for enclosed spaces).

This procedure is designed for throughput, taking 1-2 hours per test, making it suitable for quality control in production.

In the defense sector, the DEF STAN 02-713 standard is essential for reducing the risks of smoke toxicity, which accounts for up to 50 percent of fire-related deaths in confined military environments. It minimizes the release of irritants from materials in cable insulation, flooring, or structural composites, increasing survivability in emergency situations. For example, DEF STAN 02-345 is referenced for rubber pipe assemblies, providing certification support for naval, airborne, and land systems.

This standard is critical for several reasons, particularly in the context of military applications where safety, reliability and operational effectiveness are paramount.

This standard also impacts global defense suppliers, as NATO allies generally comply with this standard for interoperability. Advanced testing laboratories offer accredited services to this standard, helping manufacturers comply and reduce their liability.

Our organization, which has been serving for many years and meticulously following global developments in science and technology, conducts testing, measurement, and analysis in a wide range of areas for businesses across all sectors with a skilled team and extensive infrastructure. In this context, we also provide testing services in accordance with the standard "DEF STAN 02-713 Determination of the Toxicity Index of Combustion Products from Small Material Samples."