New Standards and Guidelines Related to the Measurement of

© 2010, TSI Incorporated

New Standards and Guidelines Related to the

Measurement of Ultrafine Particles in Ambient AirHans-Georg Horn

TSI GmbH

Aachen, Germany

MANSA, June 8th & 9th, 2010 at NPL, Teddington, UK

© 2007, TSI Incorporated© 2010, TSI Incorporated

Overview

• Standards concerning Particle Number (PN)

measurement

• Actual activities

– ISO, CEN, UN-ECE, VDI/DIN

• On the way to traceability of particle number

concentration measurements

• Summary and outlook


PN versus PM

• While ―traditional‖ PM measurements put the weight on large particles, PN measurements shift this weight to ultrafine particles (or nanoparticles).

0.01

0.1

1

10

100

1000

10000

100000

10 100 1000 10000

Dae (nm)

dN

/dlo

gD

ae [

cm

-3]

SMPS APS

0.01

0.1

1

10

100

10 100 1000 10000

Dae [nm]

dM

/dlo

gD

ae [

µg

/m³]

SMPS APS

PM PN

from: VDI 3867 Part 5


Motivation for Standardisation

• Measurement of ultra fine (or nano) particles is

expanding from:

Science Industry

Science Regulated measurements.

• Quality control becomes more important.

• Standards promote acceptance by industry and

regulators.

• Regulations require established SI traceability.


Actual Status

• Until now, standards, regulations and guidelines

that consider (or mention) PN-related

measurements are found in the following areas:– Filtration of aerosol particles

– Controlled clean environments

– Measurement of ultrafine particles / engineered nanoparticles in

workplace atmospheres

– Vehicle engine emissions

– Industrial nanoparticle characterization

– General description of measurement methods (Electrical mobility

spectrometers)

– Calibration of PN measurement devices (CPC)

– Determination of PN concentration in ambient air

– Emissions from laser printers (office equipment)

– Emissions from home furnaces (wood burning)

Established

Just released or nearly completed

Under development

Considering PN


Number Based Particle Size

Distribution Measurement• Spectrometers based on classifying particles

according to their electrical mobility are

established as widely used method for

submicrometer to nanometer size aerosol

particles.

– Examples are SMPS, DMPS, EEPS & FMPS, DMS

• Nevertheless, it took until 2009 to finally

publish a standard for this method

– ISO 15900 Differential electrical mobility analysis

for aerosol particles


ISO 15900 – Electrical Mobility

Spectrometer

DMAS is the

complete System

(like DMPS, SMPS,

FMPS etc.)

DEMC is the

classifying device

(like DMA, RDMA etc.)


ISO 15900:2009 Intention

ISO 15900:2009

Determination of particle size distribution — Differential electrical mobility analysis

for aerosol particles

Détermination de la distribution granulométrique — Analyse de mobilité électrique

différentielle pour les particules d'aérosol

• ISO 15900-2009:

– aimed at users of such equipment, not developers

– describes differential electrical mobility analysis

– tries not to discriminate against new DMA technology

– raises awareness, gives guidance on important issues:

• Slip correction factor

• Ion-particle attachment, size dependent charge distribution

• Methods for data inversion


Why use ISO 15900 – An Example

68 (2008) Nr. 11/12 - Nov./Dec.Reference: Gefahrstoffe - Reinhaltung der Luft

• The VDI working group ―Particle Counting in Ambient

Air‖ initiated a comparison of 5 mobility size

spectrometers

– 2 different manufacturers, one ―home-made‖ by IfT Leipzig

• Goal of this study was to obtain insight into the

comparability and quality of number size distribution

measurements using such mobility spectrometers

• Results were analyzed over a 5 day period, where all

instruments were running parallel, sampling at a street

canyon (Eisenbahnstrasse) in Leipzig, Germany.



• The center part of the size distributions agreed well (< 20% difference)

• Integrated particle number concentration from 40 nm to 350 nm agreed well (< 12 % difference)

• But: For small (< 20 nm) and large (> 200 nm) particles, differences occurred which were difficult

to explain without good knowledge of several parameters influencing the measurements




• All number size distributions compared within 20%, especially for the size range between 20 and 200 nm.

• Deviations increase below and above this size range.

• “The reason for these differences might be uncertainties from correction functions for particle losses, counting statistics, bipolar charge distributions used in the individual inversion routines, and the size dependent particle losses of the different sampling inlets.”



ISO 15900: Slip Correction

A measurement complies with ISO 15900 if above set of parameters is used to

calculate the slip correction. Other sets of parameters may be used, but must

be explicitly specified in the measurement report.


ISO 15900: Equilibrium Charge

Distribution

Wiedensohler

approximation

Gunn’s

model

Other charging probability functions may be used, but must be

explicitly specified in the measurement report.


ISO/TC 24/SC 4

Particle Characterisation

• What else does ISO/TC 24/SC 4 do?

– WG12 actually works on a standard for the calibration of CPCs against aerosol electrometers and against traceably calibrated reference CPCs (Watch out for ISO 27891!)

– Other WGs work on• WG1 Representation of analysis data

• WG2 Sedimentation, classification

• WG3 Pore size distribution, porosity

• WG5 Electrical sensing methods

• WG6 Laser diffraction methods

• WG7 Dynamic light scattering

• WG8 Image analysis methods

• WG9 Single particle light interaction methods

• WG10 Small angle X-ray scattering method

• WG11 Sample preparation and reference materials

• WG12 Electrical mobility and number concentration analysis for aerosol particles

• WG14 Acoustic methods

• WG15 Particle characterization by focussed beam techniques

• WG16 Characterisation of particle dispersion in liquids


On the Way to Traceable Number

Concentration Measurement

• Network of NMIs to establish traceability to SI– AIST (Japan), NPL (UK) and METAS (CH) are already on their way.

• ISO 27891 defines calibration method(s)– First draft is (nearly) finished.

• Application standards define calibration & measurement

requirements– CEN TC 264 / WG32 actually writes a TS for ambient measurment

– UN-ECE/GRPE Regs 49 and 83 for engine/vehicle emission measurement

• User Guidelines help to achieve good measurement

practice– Example: VDI/DIN 3867 Guideline series


NMI Example:

CPC Calibration at AIST

• Elaborate calibration work is done at other NMIs as well (e.g. NPL, METAS)

– NMIs will offer calibration of traceable reference devices.


ISO 27891

• ISO WD 27891 addresses traceable calibration of

condensation particle counters for measurement of

particle number concentration of aerosols.

• 2 methods of calibration permitted:

– Traceably-calibrated aerosol electrometer as the

reference

– Traceably-calibrated condensation particle counter as

the reference.

• First complete draft is (nearly) written.


CPC Calibration Method (ISO 27891)

• Traceably calibrated reference instrument (Aerosol Electrometer

or CPC) is used to calibrate other CPCs.


Application Standards

• Application standards, regulations and specifications

define calibration and measurement requirements

– UN-ECE Regulations 49 and 83 for vehicle and engine

certification

• D50 = 23 nm, D90 = 41 nm

• Linearity slope from 0 to Cmax (typically 10000 cm-3): 1 ± 0.1, R² > 0.97

• Calibration particle material PAO or equivalent (e.g. flame soot)

– CEN TS "Determination of the particle number concentration in

ambient air―

• D50 = 7 nm (preliminary), D90 (and D10) T.B.D.

• Linearity slope for 0 to Cmax : T.B.D.

• Calibration particle material: T.B.D.


CPC Calibration: Influence of the

Reference Instrument (1)

• Comparison of older (3068A) and actual (3068B) electrometer

with the AIST reference electrometerRef: Wang et al., AAAR 2007




• Characterizing and correcting losses in the reference instrument is significant

Ref: Wang et al., AAAR 2007













calibration particle material


The response of a reference CPC (Example: TSI 3772) may be biased by the

particle material used for calibration!

23

„Sucrose (2)― and „NaCl (2)― were

measured in a different experiment


User Guidelines

• Example: VDI 3867 Measurement of particulate matter in

ambient air – Methods for characterizing and monitoring test

aerosols - Determination of the particle number concentration

and particle size distribution

– Part 1: Basics

– Part 2: Condensation Particle Counter

– Part 3: Eletrical Mobility Sprectrometer

– Part 4: Optical Particle Spectrometer

– Part 5: Time-of-Flight Spectrometer

– Part 6: Electrical Low Pressure Impactor

• This series of guidelines addresses methods and their

application, it also discusses explicit instruments as examples.


Summary

• The number of application standards based on

ultrafine & nano-particle measurement is growing.

• Methodology standards and calibration standards are

necessary to ensure quality in measurement results.

• Establishing full traceability of particle number

concentration measurements is an important task;

work has started.

• The challenge is to achieve a system of guidelines,

standards and regulations which remains

homogeneous and scientifically sound.


Thank You Very Much

For Your Attention!

Any Questions?

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New Standards and Guidelines Related to the Measurement of