5 key things to know about real-time aerosol measurement ... · time aerosol measurement...

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

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+ 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

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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.

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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

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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

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2.5

8:0

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0

10

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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

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Q & A

Scott Norman, CIH, CSP

Product Specialist

TSI Incorporated

Shoreview, MN

(651) 490-2702

scott.norman@tsi.com

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