ISO 14624-3:2023

Overview

ISO 14624-3:2023 - Space systems: Determination of off-gassed compounds specifies a laboratory method to identify and quantify volatile compounds that evolve (off-gas) from materials and assembled articles intended for use in manned, pressurized spacecraft. The standard supports toxicological assessment by providing procedures to measure emissions, calculate a toxic hazard index (T), and derive safe usage limits such as maximum limit mass (MLM) or maximum limit article (MLA).

Key technical topics and requirements

• Scope: Method for volatile off-gassed compounds from materials and assemblies in habitable spacecraft volumes.
• Test atmosphere and pressure: Oxygen volume fraction ~ (20.9 ± 2) % with nitrogen/argon balance; test pressure within ±15 kPa of facility ambient. Specified impurity limits for compressed gases (e.g., CO 1 µl/l, CO2 3.0 µl/l, total hydrocarbons as methane 0.1 µl/l, halogenated compounds 0.5 µl/l, water 7.0 µl/l).
• Thermal conditioning: Standard exposure of (72 ± 1) h at (50 ± 3) °C. High‑temperature‑sensitive materials have a normative alternative at 40 °C (Annex B).
• Apparatus: Sample container, thermal chamber (±3 °C control, continuous recording), and analytical instrumentation.
• Analytical methods: Recommended instruments include gas chromatography with flame ionization detector (GC‑FID), gas chromatography/mass spectrometry (GC‑MS), and infrared spectroscopy. Formaldehyde detection capability required at 0.1 µl/l (or current SMAC).
• Sampling convention: Standard sample-mass-to-chamber-volume ratio is (5.0 ± 0.25) g/l; increase sample mass proportionally if detection limits exceed SMAC values (example provided for benzene).
• Toxicity metrics: Calculate T (toxic hazard index) by summing ratios of projected compound concentrations to their spacecraft maximum allowable concentrations (SMAC). T must be < 0.5 for evaluated materials (assumes 45 kg of material for concentration calculations unless otherwise used).
• Quality and safety: Good laboratory practice (GLP), operator health/safety precautions, and detailed test/reporting procedures are mandated.

Practical applications and who uses this standard

• Purpose: Ensure material safety and compatibility in closed, manned spacecraft atmospheres by quantifying volatile emissions and deriving allowable usage limits.
• Primary users: Aerospace materials engineers, spacecraft integrators, environmental control and life support system (ECLSS) teams, flight hardware suppliers, test laboratories, and mission toxicologists.
• Use cases: Pre‑flight material screening, comparative off‑gassing performance, support for SMAC-based risk assessments, and derivation of MLM/MLA for payload/ cabin design.

Related standards and references

• Part of the ISO 14624 series on space systems - safety and compatibility of materials. Definitions and GLP references align with ISO 14624‑1:2023. SMAC guidance examples reference publicly maintained NASA SMAC listings.

Keywords: ISO 14624-3:2023, off-gassed compounds, off-gassing testing, spacecraft materials, volatile organic compounds, toxic hazard index, SMAC, gas chromatography, thermal chamber, MLM, MLA.