Overview - ISO 21910-1:2020 (Fine bubble technology, Part 1)
ISO 21910-1:2020 specifies an off-line evaluation method for the size index of microbubbles in water. It applies to microbubbles with or without a shell within the size range 1 μm to 100 μm and defines sampling, sample transfer, retention and detection practices to produce comparable size-index results in a laboratory environment. The standard targets traceable, repeatable characterization of microbubble dispersions used across fine bubble technology applications.
Key technical topics and requirements
- Scope and applicability
- Applicable to microbubbles (gas-filled) in water, 1–100 μm; includes coated (shell) and uncoated microbubbles.
- Sampling and sample transfer
- Specifies sampling from the point of generation or dispersion in a retention container through the loading tube to the measuring instrument.
- Requirements to avoid bubble loss or adhesion in transfer lines and to control loading tube geometry, material and surface finish.
- Retention time and measurement time
- Defines “retention time” (generation → detector) and “measurement time” (stable measurement period). Emphasizes prompt measurement for larger bubbles (≥ 10 μm).
- Sample requirements
- Use of clean water diluent or blank water to control ultrafine bubble background; rinsing procedures before measurements.
- Measurement system and instruments
- Guidance on arrangement of components, pump/flow-rate considerations, and proximity of measuring instrument to generation source for unstable dispersions.
- Data, calibration and uncertainty
- Prescribes number of measurements, size categories, result reporting, calibration/traceability and uncertainty evaluation.
- Informative annexes
- Examples include dynamic image analysis (Annex A), effects of setup (Annex B), blank subtraction (Annex C), repeatability (Annex D) and inter-technique comparisons (Annex E).
Practical applications and users
ISO 21910-1 is intended for:
- Analytical laboratories performing microbubble characterization and quality control.
- Manufacturers of fine-bubble generators and microbubble measurement instruments.
- R&D teams in sectors using microbubbles: water treatment, aquaculture, agriculture, cleaning, and biomedical (e.g., contrast agents).
- Companies or testing bodies seeking inter-laboratory comparability and standardized reporting of microbubble size indices.
Practical uses include product development, process validation, performance benchmarking, and regulatory or procurement specifications where consistent microbubble sizing is needed.
Related standards and references
- ISO 21910 series (other parts cover additional characterization aspects)
- ISO 20480-2 (classification reference for microbubble behavior)
- ISO 20298-1 and ISO 13320 (terminology and measurement concepts referenced)
Keywords: ISO 21910-1, fine bubble technology, microbubble characterization, size index, off-line evaluation, sampling methods, retention time, measurement instruments.
Open preview (PDF)Fine bubble technology — Characterization of microbubbles — Part 1: Off-line evaluation of size index
