B A M - 1 0 2 2 C o n t i n u o u s B e t a G a u g e

David Gobeli, Ph.D., Thomas PottbergMet One Instruments, Inc.Grants Pass Oregon USA

Agenda

• Challenges facing continuous aerosol monitors under real-world conditions

• Moisture effect on measurement• EPA field test of BAM-1022 continuous beta

gauge• Additional field testing along Gulf Coast under

very high dew point conditions

Design Challenges in Criteria PM Monitor Design

• Must provide accurate reliable results under a wide variety of climactic conditions and aerosol types– Testing at additional sites besides those required

by EPA are useful validate known operating range to include very hot, humid regions such as US Gulf Coast

• Complexity, reliability, sensitivity, and accuracy considerations/tradeoffs

Class 3 PM2.5 Field Test

• 5 Test Campaigns, 4 Test Sites– Site A (Mira Loma CA) – winter, summer– Site B (Salt Lake City UT) – winter– Site C (Dearborn MI) – winter– Site D (Elizabeth NJ) – summer

• Site “E” (Baton Rouge LA) – year round

Salt Lake City UT – Winter 2012

Baton Rouge LA

Moisture Effect

Approach Cost Complexity Issues

Control Lower Lower Requires elevated temperature

Compensation Higher Higher Incomplete/unreliable

Removal Very High High Reliability

In-Situ Low Very Low None

Moisture Control

• Temperature – based (usually elevated) • Humidity – temperature adjusted to maintain

set point• Combination of temperature and humidity

Moisture Compensation

• Background will vary based upon moisture content (instrument artifact)– Artifacts can be subtracted out.

• Water could bind to PM and skew results if humidity too high.– Cannot be subtracted out.

Moisture Removal

• Moisture removed using physical means (PermaPure Drier)

BAM-1022 Approach

• Extremely simple• Measurement is made under near-ambient

“in-situ” conditions. • Only slight warming to prevent condensation• Nearly eliminates moisture interference• Eliminates under-measurement due to

excessive heating

Mira Loma, CA (Winter, Summer 2012)

Salt Lake City UT (Winter, 2012)

Dearborn MI (Winter, 2012)

Regression statistics Slope1 Intercept2 Correlation (r)Statistics for this test site:   0.947 -0.395 0.99035Limits for Upper: 1.100 2.000  PM2.5 Class III Lower: 0.900 -1.346 0.93793

Test Results (Pass/Fail): PASS PASS PASS

Elizabeth NJ (Summer, 2012)

Ambient Moisture Measured as

• Partial pressure of H2O in the atmosphere• Temperature and relative humidity• Dew Point

Test Site Dew Point Conditions

Baton Rouge Test Site

• Indicative of Gulf Coast/Southeast US Weather Conditions– Extremely high dew point during summer months– Wildly varying dew point and temperature during

winter months• EPA “Class 3” style field test performed for

almost 1 year– Triplicate BAM-1022 monitors & FRM samplers– Strict collocation, all Class 3 protocols followed

Baton Rouge – Dew Point

All Data

Summer Only

Winter Only

Summary

• Additional test sites demonstrates “in-situ” approach under expanded ambient/climactic conditions

• Baton Rouge site conditions unlikely to be duplicated in EPA sites A-D for Class 3 test.

• Additional testing currently underway for ultra-high sensitivity version with PTFE filter media.

Questions

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