ISO 16000-42:2023

Overview

ISO 16000-42:2023 - "Indoor air - Part 42: Measurement of the particle number concentration by condensation particle counters" provides standardized methods and strategies for measuring the particle number concentration in indoor environments using a condensation particle counter (CPC). The standard covers particles roughly from 10 nm to 3 µm, and notes that measured counts are often dominated by the ultrafine particle (UFP) fraction (≤100 nm), so CPC results can approximate UFP concentrations. It also sets out quality assurance, uncertainty evaluation and minimal reporting requirements for indoor particle number measurements. Chemical characterization and targeted bioaerosol analysis are outside the scope (though CPCs can register some bioaerosols).

Key technical topics and requirements

• Measurement principle: use of CPC technology (working fluid, optical detection after enlargement) to obtain total particle number concentration.
• Size range and detection: guidance on minimal detection size, detection efficiency and interpretation of CPC results for particles ~10 nm to 3 µm.
• Instrument requirements: minimal CPC performance, nominal and factory-certified flow rates, and instrument settings checks.
• Sampling and strategy: practical sampling recommendations for indoor environments (placement, averaging, temporal resolution).
• Measurement strategies: procedures for estimating average room concentration, assessing resting vs active states, source investigation, infiltration from outdoors or adjoining rooms, measurement in vehicle cabins, and evaluating mitigation success.
• Quality assurance & uncertainty: instrument performance checks (zero/leak tests), periodic calibration, and methods to estimate measurement uncertainty.
• Reporting & interpretation: minimal information to include in reports and contextual checklist items to aid interpretation.
• Informative annexes: real-world concentration examples, particle size distribution methods (DMAS), water-based CPC considerations, and a measurement checklist.

Practical applications and who uses this standard

• Indoor air quality (IAQ) consultants and field technicians conducting particle number monitoring.
• Environmental and occupational health laboratories seeking reproducible CPC-based measurements.
• Building engineers and HVAC professionals assessing ventilation effectiveness, infiltration, or remediation success.
• Researchers studying UFP exposures, source emissions (cooking, smoking, combustion, equipment), and indoor particle dynamics.
• Regulators and policymakers developing indoor air assessment protocols or guidance.

Use cases include baseline IAQ surveys, source identification, evaluating control/mitigation measures (filtration, ventilation), and exposure assessment in homes, offices, schools and vehicle cabins.

Related standards

• ISO 16000-1 - General aspects of sampling strategy (indoor air)
• ISO 16000-34 - Strategies for measurement of airborne particles
• ISO 27891 - Calibration of condensation particle counters
• CEN/TS 16976 - Ambient air particle number concentration methods

Keywords: ISO 16000-42:2023, indoor air, particle number concentration, condensation particle counter, CPC, ultrafine particles, UFP, measurement strategy, quality assurance, indoor environments.