Overview
EN ISO 4589-2:2017 - "Plastics - Determination of burning behaviour by oxygen index - Part 2: Ambient-temperature test" - specifies laboratory methods to determine the oxygen index (OI): the minimum volume fraction of oxygen in an oxygen/nitrogen atmosphere that will support combustion of small vertical plastic specimens under defined conditions. Results are reported as OI values and are useful for comparative flammability assessment and quality control of plastics.
Key topics and requirements
- Scope of materials: Methods are for self-supporting vertical bars or sheets up to 10.5 mm thick. Applicable to solid, laminated or cellular materials with apparent density ≥ 100 kg/m³; may also apply to some lower-density cellular materials. A method for flexible sheets/films supported vertically is included.
- Test principle: Vary oxygen concentration in a calibrated test chimney and observe whether a specimen sustains burning to determine the OI.
- Apparatus and equipment (specified at a conceptual level):
- Test chimney and specimen holder
- Gas supplies and flow/control devices
- Oxygen analyser and calibration procedure
- Igniter, timing devices and fume extraction
- Specimen preparation and conditioning: Sampling, dimensions, marking, and ambient conditioning are required to ensure repeatable results.
- Ignition procedures: Two ignition modes are specified - top surface ignition (Procedure A) and propagating ignition (Procedure B) - with guidance on assessment of burning behaviour for each.
- Data handling: Instructions for selecting successive oxygen fractions, calculating the oxygen index, determining statistical parameters (k, standard deviation) and reporting precision.
- Short procedure: A comparative method to determine whether OI exceeds a specified minimum value.
- Normative and informative annexes: Include calibration, OI calculation methods, typical test sheets and interlaboratory precision data.
Practical applications and users
- Who uses it:
- Materials manufacturers and compounders for product development and batch quality control
- Independent laboratories performing flammability and compliance testing
- Product designers and safety engineers assessing material fire performance
- Regulatory bodies and procurement teams specifying minimum fire-performance criteria
- Where it's applied:
- Comparative flammability ranking of plastics and films
- Screening materials for use in products where ambient-temperature burning behaviour matters
- Supporting classification, specification and compliance claims (in conjunction with other fire tests)
- Limitations: OI is a controlled-laboratory indicator; results depend on specimen shape, thickness, orientation and ignition method and are not a complete measure of real-world fire behaviour.
Related standards
- EN ISO 4589 is a series - refer to other parts of the ISO 4589 series for additional test conditions and complementary methods (e.g., elevated-temperature tests). Check ISO/CEN listings for applicable adjacent standards.
Keywords: EN ISO 4589-2:2017, oxygen index (OI), oxygen index test, plastics burning behaviour, ambient-temperature test, flammability testing, material testing standard.