ISO 27891:2015

Overview

ISO 27891:2015 - Aerosol particle number concentration: Calibration of condensation particle counters (CPCs) - specifies laboratory methods to determine the detection efficiency and associated measurement uncertainty of CPCs. The standard covers particle number concentrations from 1 cm‑3 to 1×10^5 cm‑3 and particle sizes from approximately 5 nm to 1 000 nm, and is applicable to CPCs with inlet flows of about 0.1 l/min to 5 l/min. It supports both determination of a CPC calibration factor (the plateau efficiency across larger particle sizes) and characterization of the efficiency decline near the lower detection limit.

Key topics and technical requirements

• Detection efficiency measurement across particle sizes (≈5 nm–1000 nm) and concentrations (1–1×10^5 cm‑3).
• Calibration approaches using either a reference instrument (FCAE) or a reference CPC; procedures for setup, adjustment, and measurement are described.
• Required components and checks: primary aerosol source, charge conditioner, DEMC, make‑up/bleed air, mixing/splitter tubing, reference instrument, and tools for flow and size control.
• Splitter bias (β) and concentration bias correction between instrument inlets - methods for evaluation and correction.
• Uncertainty estimation: method to calculate measurement uncertainty for detection efficiency and particle number concentration.
• Reporting and traceability: guidance for calibration certificates, reporting of results, and annexes with worked examples and normative calculations (e.g., Annex D calculation of detection efficiency; Annex C example certificates).
• Annex material: informative and normative annexes on CPC performance characteristics, effects of particle surface properties, diluters, flow calibration, and extending calibration to lower concentrations.

Practical applications and users

Who benefits from ISO 27891:2015:

• Calibration and metrology laboratories performing CPC calibrations and issuing calibration certificates.
• CPC manufacturers validating instrument performance and specifying detection limits.
• Environmental monitoring and air quality networks ensuring instrument comparability and traceability.
• Research laboratories in aerosol science, nanotechnology, and atmospheric studies that require accurate particle number concentration measurements.
• Occupational hygiene and industrial hygiene teams that use CPCs for workplace aerosol monitoring.

Practical benefits:

• Harmonized, traceable calibration procedures that improve comparability between CPCs and networks.
• Clear methods to quantify and report uncertainty and size‑dependent efficiency, supporting compliance, instrument selection, and quality assurance.

Related standards and references

• ISO 27891:2015 was developed under ISO/TC 24 (Particle characterization). Users should consult the normative references and ISO/IEC Directives for conformity assessment and traceability guidance included in the standard.