ISO 19996:2024
(Main)Charge conditioning of aerosol particles for particle characterization and the generation of calibration and test aerosols
Charge conditioning of aerosol particles for particle characterization and the generation of calibration and test aerosols
This document specifies requirements and provides guidance for the use of charge conditioners for aerosol particles, especially for particle characterization and for the generation of calibration and test aerosols. This document provides a methodology to specify the performance of charge conditioners and for adequate quality control, with respect to their application in: — particle size and concentration measurement with differential mobility analysing systems (DMAS); —particle size classification with differential electrical mobility classifiers (DEMC). For these applications, this document covers particle charge conditioning for particle sizes ranging from approximately 1 nm to 1 µm and for particle number concentrations at the inlet of the charge conditioner up to approximately 107 cm-3. This document does not address specific charge conditioner designs or other applications besides those specified in Clause 1. Radiation safety for charge conditioners with radioactive sources or x-ray tubes is not covered by this document.
Conditionnement de la charge (électrique) des particules d'aérosols pour la caractérisation de particules et la génération d'aérosols pour calibration et essais
General Information
Standards Content (Sample)
International
Standard
ISO 19996
First edition
Charge conditioning of
2024-10
aerosol particles for particle
characterization and the generation
of calibration and test aerosols
Conditionnement de la charge (électrique) des particules
d'aérosols pour la caractérisation de particules et la génération
d'aérosols pour calibration et essais
Reference number
© ISO 2024
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ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 2
5 General principle . 2
5.1 General .2
5.2 Ionization sources .3
5.2.1 General .3
5.2.2 Sources with radioisotopes .3
5.2.3 Soft X-ray sources .5
5.2.4 Corona discharge .6
5.3 Charge conditioning .7
5.3.1 General .7
5.3.2 Bipolar charge conditioners .7
5.3.3 Unipolar charge conditioners .8
5.4 The charge distribution function .9
5.4.1 General .9
5.4.2 Charge distribution function for radioactive bipolar charge conditioners .9
5.4.3 Charge distribution functions for other bipolar and unipolar charge conditioners .9
6 Factors influencing the resulting charge distribution .10
6.1 General .10
6.2 Aerosol particle characteristics influencing the charge distribution .10
6.2.1 Particle size and surface area .10
6.2.2 Particle number and surface area size distribution and concentration . 12
6.2.3 Particle pre-charge . . 12
6.3 Aerosol carrier gas characteristics influencing the charge distribution . 13
6.3.1 Carrier gas composition . 13
6.3.2 Carrier gas pressure and temperature . 13
6.3.3 Carrier gas humidity . 13
6.4 Charge conditioner operating parameters influencing the charge distribution . 13
6.4.1 Aerosol flow rate . 13
6.4.2 Ion production rate .14
6.5 Others .14
6.5.1 Surplus ions downstream of device .14
6.5.2 Particle losses to the chamber wall .14
6.5.3 Aerosol dilution in the charge conditioner . 15
6.5.4 Generation of artefact particles . 15
7 Operational parameters for device specification .15
8 Test procedures for determining the suitability of charge conditioners .15
8.1 Guidance to test procedures in the annexes . 15
8.2 Charge conditioner performance verification .16
8.3 Particle losses in a charge conditioner . .16
8.4 Particle generation rate .16
8.5 Charge distribution of bipolar charge conditioners .16
9 Cleaning and maintenance including safety issues . 17
Annex A (informative) Implementation of bipolar steady-state charge conditioning .18
Annex B (informative) Performance test procedures for charge conditioners .24
Annex C (informative) Electrostatic precipitator to provide uncharged aerosol particles .37
iii
Annex D (informative) Concentration series test for charge conditioners .39
Annex E (informative) Example set of tests for bipolar charge conditioners .45
Annex F (informative) Test method for bipolar charge conditioners with ambient aerosols .53
Bibliography .55
iv
Foreword
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v
Introduction
Charge conditioning of aerosol particles is the crucial process of establishing a known, size-dependent charge
distribution on aerosol particles. Different designs for charge conditioners exist. In charge conditioners,
aerosol particles are exposed to a cloud of ions of either both positive and negative polarities (bipolar charge
conditioners) or a single polarity (unipolar charge conditioners).
The transport of the ions to the aerosol particles can either be driven by Brownian motion of the ions
(diffusion charging) or by an electrical field (field charging). Since field charging is strongly biased by a
particle’s electrical properties (namely the relative permittivity), diffusion charging is generally used to
condition aerosol particles:
— for particle size distribution measurement with the differential mobility analysing system (DMAS);
— for particle size classification with the differential electrical mobility classifier (DEMC).
Several parameters determine whether or not charge conditioning achieves its goal of either generating a
mathematically describable bipolar steady-state charge distribution or a quantifiable unipolar mean charge.
Examples for
...
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