new standards and guidelines related to the measurement of
TRANSCRIPT
© 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
© 2007, TSI Incorporated© 2010, TSI Incorporated
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
© 2007, TSI Incorporated© 2010, TSI Incorporated
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.
© 2007, TSI Incorporated© 2010, TSI Incorporated
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
© 2007, TSI Incorporated© 2010, TSI Incorporated
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
© 2007, TSI Incorporated© 2010, TSI Incorporated
ISO 15900 – Electrical Mobility
Spectrometer
DMAS is the
complete System
(like DMPS, SMPS,
FMPS etc.)
DEMC is the
classifying device
(like DMA, RDMA etc.)
© 2007, TSI Incorporated© 2010, TSI Incorporated
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
© 2007, TSI Incorporated© 2010, TSI Incorporated
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.
© 2007, TSI Incorporated© 2010, TSI Incorporated
Why use ISO 15900 – An Example
• 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
68 (2008) Nr. 11/12 - Nov./Dec.Reference: Gefahrstoffe - Reinhaltung der Luft
© 2007, TSI Incorporated© 2010, TSI Incorporated
Why use ISO 15900 – An Example
• 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.”
68 (2008) Nr. 11/12 - Nov./Dec.Reference: Gefahrstoffe - Reinhaltung der Luft
© 2007, TSI Incorporated© 2010, TSI Incorporated
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.
© 2007, TSI Incorporated© 2010, TSI Incorporated
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.
© 2007, TSI Incorporated© 2010, TSI Incorporated
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
© 2007, TSI Incorporated© 2010, TSI Incorporated
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
© 2007, TSI Incorporated© 2010, TSI Incorporated
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.
© 2007, TSI Incorporated© 2010, TSI Incorporated
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.
© 2007, TSI Incorporated© 2010, TSI Incorporated
CPC Calibration Method (ISO 27891)
• Traceably calibrated reference instrument (Aerosol Electrometer
or CPC) is used to calibrate other CPCs.
© 2007, TSI Incorporated© 2010, TSI Incorporated
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.
© 2007, TSI Incorporated© 2010, TSI Incorporated
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
© 2007, TSI Incorporated© 2010, TSI Incorporated
CPC Calibration: Influence of the
Reference Instrument (2)
• Characterizing and correcting losses in the reference instrument is significant
Ref: Wang et al., AAAR 2007
© 2007, TSI Incorporated© 2010, TSI Incorporated
CPC Calibration: Influence of the
Reference Instrument (2)
• Characterizing and correcting losses in the reference instrument is significant
Ref: Wang et al., AAAR 2007
© 2007, TSI Incorporated© 2010, TSI Incorporated
CPC Calibration: Influence of the
Reference Instrument (2)
• Characterizing and correcting losses in the reference instrument is significant
Ref: Wang et al., AAAR 2007
© 2007, TSI Incorporated© 2010, TSI Incorporated
CPC Calibration: Influence of the
calibration particle material
Ref: Wang et al., AAAR 2007
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
© 2007, TSI Incorporated© 2010, TSI Incorporated
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.
© 2007, TSI Incorporated© 2010, TSI Incorporated
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.
© 2007, TSI Incorporated© 2010, TSI Incorporated
Thank You Very Much
For Your Attention!
Any Questions?