Overview
ISO 14624-1:2023 - "Space systems - Safety and compatibility of materials - Part 1: Determination of upward flammability of materials" defines a standardized laboratory method to evaluate the upward flammability behavior of aerospace materials. The test determines whether a material exposed to a defined ignition source will self‑extinguish, avoid transfer of burning debris, and therefore not ignite adjacent materials under specified atmospheric conditions. This second edition updates test provisions and annexes to align flammability assessment with current space‑system safety needs.
Keywords: ISO 14624-1, upward flammability, space systems, aerospace materials, flammability test, material safety
Key topics and technical requirements
- Test principle: A validated chemical ignitor is applied to the lower end of a vertically oriented specimen in an oxygen/nitrogen atmosphere; burn length and debris transfer are recorded.
- Specimen dimensions: Standard specimen minimums - length 300 mm, width 60 mm (75 mm for thin-film), thickness = use minimum in‑service thickness but ≤ 25 mm (excluding substrate).
- Pass/fail criterion: Material is considered to self‑extinguish if burn length ≤ 150 mm. Failure of any single specimen constitutes failure for that test environment.
- Replicates: At least five standard specimens are tested.
- Atmospheric control: Ambient reference = O2 20.9% ± 0.2%, pressure 101.4 kPa ± 5 kPa, temperature 23 °C ± 5 °C. Test gas purities and oxygen concentration accuracy are specified. Post‑test gas analysis (CO and CO2) is required and reported.
- Ignitor and equipment: Chemical ignitor requirements (e.g., ~1 100 °C in ambient) and a test chamber sized to limit O2 depletion to ≤ 5% are specified.
- Flammability thresholds: Definitions and procedures for Maximum Allowable Oxygen Concentration (MOC) and Upward Limiting Oxygen Index (ULOI) are provided, with annexes for threshold approximation and higher‑precision methods.
- Good laboratory practice (GLP): Repeatability checks and use of reference materials for quality assurance are required.
Practical applications and users
ISO 14624-1 is intended for:
- Spacecraft and payload designers assessing material safety and compatibility.
- Materials engineers and suppliers qualifying candidate materials (foams, laminates, fabrics, coatings).
- Test laboratories performing flammability certification and compliance testing.
- Safety engineers, certification authorities, and procurement teams specifying materials for crewed and uncrewed spacecraft.
Use cases include material selection for cabins, equipment enclosures, harnessing, interior finishes, and worst‑case configuration testing where elevated oxygen concentration or altered geometry may increase flammability risk.
Related standards
- ISO 14624 series (other parts on ISO website) - for broader safety and compatibility of space materials.
- ISO/TS 16697 - referenced for threshold approximation procedures and flammability threshold determination.
For implementing ISO 14624-1:2023, consult the full standard and annexes for detailed procedures, ignitor preparation, data‑reporting templates, and GLP guidance.