ISO 3529-1:2019

Overview - ISO 3529-1:2019 (Vacuum technology - Vocabulary - Part 1: General terms)

ISO 3529-1:2019 is an international vocabulary standard that defines general terms used in vacuum technology. Its purpose is to give theoretically precise definitions while keeping them practical for engineering, research and industrial use. The second edition (2019) updates the original 1981 edition with clarified vacuum ranges, new terms (for example ultra clean vacuum) and additional concepts such as Knudsen number and slip flow. The standard also includes symbols and abbreviated terms commonly used in vacuum science.

Key topics covered

• General definitions of vacuum, partial pressure, total pressure and pressure of a vacuum (surface and bulk meanings).
• Classification of ranges of vacuum (rough/low, medium/fine, high, ultra‑high, extreme‑high) with reasoning for typical limits and practical circumstances.
• Terms describing gases and vapours: gas, non‑condensable gas, vapour, saturation vapour pressure, degree of saturation.
• Gas state and transport parameters: number density, unitary mass density, bulk velocity, temperature, and pV (quantity of gas in pressure‑volume units).
• Flow and kinetic concepts: mean free path, Knudsen number, rarefaction parameter, collision rate, diffusion, diffusion coefficient.
• Flow regimes and mechanisms: viscous flow (including Poiseuille/Hagen‑Poiseuille), molecular flow, intermediate/transitional flow, slip flow, effusion, transpiration, thermal transpiration.
• Flux and flow rate quantities: molecular flux, throughput, mass/volume/molar flow rates.
• Statistical/velocity distributions (e.g., Maxwellian velocity distribution), plus a dedicated section of symbols and abbreviations.

Note: the introduction advises consulting measurement‑specific standards when practical measurement interpretation is required.

Applications and who uses this standard

• Vacuum and surface scientists, vacuum system designers and engineers (semiconductor fabrication, thin‑film coating, electron microscopy).
• Manufacturers and specifiers of vacuum pumps, chambers, seals and instrumentation.
• Metrology labs, research institutions and quality managers who need consistent terminology for procurement, documentation and testing.
• Educators and standards specialists for training and harmonizing technical vocabulary across industries.

Using ISO 3529-1:2019 helps ensure clear communication about pressure ranges, flow regimes and gas behavior in vacuum systems - essential for design, operation, troubleshooting and regulatory compliance.

Related standards and guidance

• ISO/TC 112 (Vacuum technology) publications and measurement standards referenced for practical interpretation.
• ISO Online Browsing Platform and IEC Electropedia for terminological cross‑references and authoritative symbol lists.

Keywords: ISO 3529-1:2019, vacuum technology vocabulary, vacuum ranges, mean free path, Knudsen number, molecular flow, UHV, vacuum terminology.