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5 key things to know about
real-time aerosol
measurement instruments
Scott Norman, CIH CSP
Product Specialist
TSI Incorporated
Shoreview MN
9/24/2015© TSI Incorporated
Sept 24, 2015 RAECO Webinar
Goal – to appreciate the value of real-time aerosol measurement instruments.
What are aerosols
How are aerosols measured
Types of real time aerosol instruments
1. How light scattering photometric instruments work
2. Strengths and limitations of photometric aerosol instruments
3. The value of real-time, logged data
4. Case Studies and application examples
5. Demonstrated return on investment
Wrap up / Q&A
9/24/2015© TSI Incorporated 2
+ Dust
What are Aerosols
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+ Dust
+ Fume
What are Aerosols
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+ Dust
+ Fume
+ Mist
What are Aerosols
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+ Dust
+ Fume
+ Mist
+ Smoke
What are Aerosols
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Aerosol Size Matters
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Respiratory Tract
Based on International Commission of Radiological Protection (1994) and U.S. Environmental Protection Agency (1996a).
Air Quality Criteria for Particulate matter, 2004, p 6-5.
Extrathoracic region
Tracheobronchial (TB)
region
Alveolar (A) region
>PM10
PM10-PM2.5
PM2.5
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How are aerosols measured
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Gravimetric SamplingSampling PumpSample mediaSampling trainFlow calibratorLaboratory analysis or microbalance
How fast do you need the
data?
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Aerial photograph of Manhattan, NY. Sept 12, 2001Wikipedia, source NASA
Do we evacuate or shelter?
This image cannot currently be displayed.
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U.S. Air Force photo/Master Sgt. Wally Baciohttps://www.flickr.com/photos/chucksimmins/2857833739
Measurement of Aerosols
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Gravimetric SamplingSampling PumpSample mediaSampling trainFlow calibratorLaboratory analysis or microbalance
Real time measurement
instruments
+ Speedometer
+ Altimeter
+ Thermometer
+ scale
+ Noise meter
+ Data logging dosimeter
+ RF Survey meter
+ PID / FID
+ Geiger counter
+ Confined Space 4-gas monitor
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“Do you know how fast you
were going?”
http://www.flickr.com/photos/oregondot/3698915292/
Oregon Department of Transportation
Types of real time aerosol
monitoring instruments
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+ Beta Attenuation Monitor (BAM)
+ Tapered Element Oscillating Microbalance (TEOM)
+ Piezoelectric microbalance
+ Aerodynamic Particle Sizer (APS)
+ Differential Mobility Analyzer Spectrometer (DMS)
+ Integrating Nephelometer (Photometer)
+ Condensation Particle Counter (CPC)
+ Optical Particle Counter (OPC)
“IH-based” field instruments
+ Photometers
+ Optical Particle Counters
+ Condensation Particle Counters
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DustTrak™ DRX 8533Photometer
AeroTrak® 9306 OPC
P-Trak® 8525CPC
Light Scattering Photometer
Technology
Photo
Detector
Laser Diode
Light Trap
Aerosol Inlet
Sheath Air
Mirror
Gravimetric Filter
Beam Shaping
OpticsViewing
Volume
OpticsChamber
Orifice
HEPA Filter
Exhaust
Flowmeter
Pump
Protection
Filter
Dampening Chamber
Laser
Beam
16
8533 DustTrak™ DRX
© TSI Incorporated 9/24/2015
Optical Particle Counter
(OPC)Optical Particle Counter (OPC) – light scattered by individual particles
traversing a light beam is detected at various angle. These signals are
interpreted in terms of particle size via calibrations. The TSI Aerotrak
Handheld Particle Counter 9303 and 9306 use this technology.
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Condensation Particle Counter
(CPC)
Condensation Nuclei Counter
(aka Condensation Particle
Counter) – This methodology uses
a condensing liquid (alcohol or
water) to grow the particle size
large enough to be counted
optically. These instrument s
count numbers of particles, not
mass concentration. The TSI
PortaCount and P-Trak use this
technology.
7/24/2014© TSI Incorporated 18
0.001 0.01 0.1 1 10 100Particle Size Range (micrometers)
Typ
es
of
Pa
rtic
les
BacteriaVirus
Oil Smoke
Diesel Engine Exhaust
Combustion Nuclei
Soot
Inhalable
(Total dust)
Respirable
Thoracic
Pollen
Particle Sizes
Construction Activities
Carbon Black
Welding Fume
4
Sea salt
Tobacco smokeCoal Dust (mining)
Paint Pigment
Vacuuming
Wind blown dust
Volcanic emissions
Environmental / Naturally Occurring Particles
Workplace / man-made Particles
Fly Ash
Nanoparticle
0.001 0.01 0.1 1 10 100Particle Size Range (micrometers)
Inhalable
(Total dust)TSPRespirable
Thoracic Particle Size Range for
Aerosol Instruments
Photometer
CPC-alcohol
OPC
Diffusion Charger
4
Optical Particle Counter 0.3 to 25 µm
Condensation Particle Counter 0.02 to 1 µm
Photometer: 0.1 to 15 µm
CPC - Water
SMPS
Nanoparticle
Aerosol concentration
measurement range
+ Photometers 0.001 – 150 mg/m3
+ Optical Particle Counters 0 – 200,000 particles/cc
+ Condensation Particle Counters 0 - 500,000 particles/cc
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1. How light scattering
photometric instruments work
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Physics of aerosols
Properties
Behavior
Measurements
Aerosol Basics
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Aerosol Characteristics
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Size
Shape
Density
Aerodynamic diameter
Not all particles are spheres
Mass concentration is calculated
from known density
Aerosol properties
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• Aerosols absorb, reflect, refract and diffract light
• Light passing through an aerosol concentration is
affected by the properties of the aerosol.
Light Scattering Photometer
Technology
Photo
Detector
Laser Diode
Light Trap
Aerosol Inlet
Sheath Air
Mirror
Gravimetric Filter
Beam Shaping
OpticsViewing
Volume
OpticsChamber
Orifice
HEPA Filter
Exhaust
Flowmeter
Pump
Protection
Filter
Dampening Chamber
Laser
Beam
26
8533 DustTrak DRX
© TSI Incorporated 9/24/2015
Particle counting vs. light scattering
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Particle counting is like counting
the number of rain drops or snow
flakes that hits the window
OPCs count the number of
raindrops (or snow flakes)
hitting the windshield.
• Works for certain size drops at
low concentration levels
CPCs count the number of
ultrafine particles
Photometers measure the
amount of light scattered by the
fog.
Think of how bright the fog is in
the headlights.
“thicker fog” is brighter.
A photometer would calculate
more mass based on a brighter
response from thicker fog based
on the calibration aerosol.
Photometric light scattering
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Calibration aerosol
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Photometers are calibrated to a
known test aerosol.
• known density
• known refractive index
• known size distribution
A bucket of golf balls will not
weigh the same as a bucket of
ping pong balls.
The photometer sees Ping Pong
balls, but calculates mass
concentration based on the
calibration aerosol (golf balls)
Calibration factors are developed
to ‘inform’ the instrument that
the sampled aerosol is different
than the test aerosol. Thus the
mass measurement needs
correction.
Density
Size
Refractive index
Calibration factor
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Aerosol distribution
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A photometer sees aerosols of all
shapes and sizes
The photometer measures the
light scattering of these particles
as a group.
Mass is calculated based on the
properties of the calibration
aerosol.
Fly ash – FHWA.dot.gov
2. Strengths and limitations of
photometric aerosol instruments
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limitations
Calibrated to test aerosol
Humidity effects
Contaminated optics
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Calibrated to test aerosol
+ Precise instrument response to all aerosol
+ Response to aerosol similar to calibration
aerosol will more closely match actual
gravimetric result
+ Use side-by-side gravimetric results to develop
custom calibration factors (K factors)
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Humidity effect
+ Hygroscopic aerosols swell as humidity levels
increase
+ Photometric instrument readings will be
elevated in humid conditions
+ Inlet conditioners to reduce the effects of
humidity are added to photometric instruments
for long term environmental monitoring
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Optic contamination
+ High aerosol levels can result in contaminated
optics and measurement drift
+ Zeroing the instrument regularly helps correct
+ Use size selective inlet conditioners to sample
only small size fractions
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Strengths
Real-time
Data logging
Alarms
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3. The value of real-time data
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“How far down wind do we need to evacuate people?”
Data logging
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Average = 0.527 mg/m3
Alarms
+ Audible or visual notification at selected levels.
+ Stop the work and adjust engineering controls
+ Prevents exposure, prevents complaints
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4. Case studies and application
examples
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Optical Particle CounterClean Room Certification
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NASAhttps://commons.wikimedia.org/wiki/File:MSL_Rover_Environmental_Monitoring_Station.jpg
FED-STD 209E
ISO 14644-1 Cleanroom Classification
Number of particles of various size per unit volume
+ Construction on 1st floor of
hospital.
+ Nurses on 2nd floor above
construction complaining of
odors and headaches.
+ High concentration of ultrafine
particles found coming through
expansion joint.
+ Duct Tape applied to joint,
complaints ceased.
P-Trak Ultrafine Particle CounterConstruction below nurses station
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+ Track wind, weather and aerosol concentration
+ Logging data for community awareness
+ Action level for dust suppression activities
Perimeter monitoring
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5. Return on investmentFoundry ventilation project
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0
0.5
1
1.5
2
2.5
8:0
0
8:3
0
9:0
0
9:3
0
10
:00
10
:30
11
:00
11
:30
12
:00
12
:30
13
:00
13
:30
14
:00
14
:30
15
:00
15
:30
16
:00
mg
/m
3
Time
Simulated Personal Exposure
Data
+ Recent large engineering control investment (ventilation)
+ One person sampled high for silica on follow up
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Nanoparticles / ultrafine particles
+ high number concentration
+ very low mass
Future metrics
Swiss Regulation 941.242
+ Solid particle number concentration downstream of the Diesel
Particulate Filter must be below 250,000 particles/cc
Future considerations
Summary
+ How photometric instruments work
+ Strengths and limitations
+ Value of real-time, logged data
+ Case studies
+ Demonstrated return on investment
9/24/2015© TSI Incorporated 47
Q & A
Scott Norman, CIH, CSP
Product Specialist
TSI Incorporated
Shoreview, MN
(651) 490-2702
9/24/2015© TSI Incorporated 48