EPA 2003 Blind Audit of Protocol Gases

John Schakenbach, USEPA, CAMDScott Shanklin, Cadmus Group

Bob Wright, USEPA, ORD

EPRI CEM User GroupMilwaukee, WIMay 4-6, 2004

What is the Problem?

Historically, blind audits of calibration gases have shown poor quality initially

SO2 RATA using plant’s incorrect cal gas (low by 15%). Source could underreport SO2 by 15% and be undetected for at least 6 months.

Other Reasons Why Accurate Cal Gas is Important

Only daily assurance CEM is really working

Reference Method analyzers need accurate calibration gases to produce accurate RATA results

Purpose of Blind Audits

Help vendors improve gas quality Help sources identify good vendors

History 1970’s -1996 EPA audited gases Posted results

– In 1995, one vendor off by -16.3% (CEM would underreport)

Strong utility and vendor support Auditing strongly correlated with improved

gas quality

Current Gas Analysis First audit in 7 years Blind audit 14 national gas vendors Similar procedures as in past SRMs and NTRMs used 42 Protocol tri-blend cylinders MACTEC (UV and NDIR) and Spectral

Insights (FTIR)

Tri-blend Protocol GasesCO2(%)

NO(ppm)

SO2(ppm)

Low 5 50 50

Medium 12 400 500

High 18 900 1000

Instrumentation NO - API Model 200AH chemiluminescence NO - AMETEK Model 922M differential absorption

UV SO2 - Bovar Model 721M differential absorption

UV CO2 - California Analytical Model 3300A NDIR NO, SO2 and CO2 - Nicolet Nexus Model 760 FTIR Environics (Graseby-Nutech) Series 3740 gas

dilution system

UHP N2

Zero

CO2

Reference

NOReference

SO2

Reference

CandidateStandard

CandidateStandard

CandidateStandard

PressureRegulator

GasFlow Selector

PressureGauge

CAI 3300A CO2

Analyzer

AMETEK 922M NOx

Analyzer

AnalogDigital

Converter

DataAcquisition

PC

Bovar 721M SO2 Analyzer

Schematic of Mactec Assay Apparatus

Vent

Candidate, Zero, SRM or NTRM Gas Standards

FTIR Spectrometer

Cel

l

Vacuum Pump

Selector Valve

Isolation Valves

Vent

PT

Computer

Transducers

Check Valves

Toggle Valves

Vent

Gas Manifold/Regulator

Manifold Vent Valve

Vent

Spectral Insights Assay Apparatus

Accuracy Criterion

Part 75, Appendix A, sec 5.1.4 requires 2.0% of tag value

Protocol procedures achieve +2% of tag value:

1% Standard Reference Material

plus1% EPA Protocol methodology

Problems CO2 quenching biased the NO concs from

chemiluminescent analyzer low– Chemiluminescent NO concs thrown out– Measurements repeated with a UV analyzer

UV analyzer was set up for 0 - 500 ppm NO, but should have been for 0-1000 ppm– Threw out high level NO concs– Repeated high level NO measurements using FTIR

Problems SO2 interfered with UV analyzer NO

readings– Injected SO2 in N2 to develop a correction

Ran out of high level CO2 SRM for FTIR– Threw out the high level CO2 FTIR results and

relied on NDIR

Results EPA presents the following information without

assigning a rating to the gas vendors. If EPA’s and vendor’s values differ by 2.0% or less,

then because of uncertainties in the measurement system, statistically, there is no difference between the two values, e.g., a difference of 2.0% and 0.5% are considered equal.

All vendors that failed are re-analyzing their gas cylinders. When EPA receives the re-analyzed results, they will be posted.

Gas

Conc. Tag ValueAudit

Tag ValueAudit

Tag Value Audit

Level (ppm NO) Result (ppm SO2) Result (% CO2) Result

Air Liquide Low 54.0 Pass 47.5 Pass 4.97 PassAir Liquide Mid 401 Pass 499 Pass 12.1 PassAir Liquide (a) High 911 Pass 981 Pass 17.7 Fail

Airgas Southwest Specialty Gases (a) Low 48.90 Fail 47.73 Pass 5.01 PassAirgas Southwest Specialty Gases Mid 406.0 Pass 496.8 Pass 12.00 PassAirgas Southwest Specialty Gases (a) High 900.0 Fail 994.6 Pass 17.99 Pass

Airgas NCN Specialty Gases Low 51.4 Pass 50.4 Pass 5.01 PassAirgas NCN Specialty Gases Mid 388 Pass 500 Pass 12.0 PassAirgas NCN Specialty Gases (a) High 845 Fail 1000 Pass 18.0 Pass

Airgas South Specialty Gases (a) Low 50.05 Fail 50.23 Pass 5.041 PassAirgas South Specialty Gases Mid 397.5 Pass 502.8 Pass 12.00 PassAirgas South Specialty Gases High 900.0 Pass 998.8 Pass 18.07 Pass

BOC Gases Low 49.8 Pass 50.9 Pass 5.00 PassBOC Gases (a) Mid 407.8 Fail 500.4 Pass 11.98 PassBOC Gases (a) High 900 Fail 1000 Pass 18.02 Pass

AGA / Linde Gas Group Low 50.4 Pass 48.7 Pass 5.20 PassAGA / Linde Gas Group Mid 396 Pass 466 Pass 12.5 PassAGA / Linde Gas Group High 904 Pass 956 Pass 18.3 Pass

Matheson Tri-Gas (a) Low 48.9 Fail 49.5 Pass 5.23 FailMatheson Tri-Gas (a) Mid 410 Fail 504 Pass 12.2 PassMatheson Tri-Gas High 904 Pass 988 Pass 17.9 Pass

Gas Vendor

NO SO2 CO2

Gas

Conc.Tag

Value AuditTag Value

AuditTag

Value AuditLevel (ppm NO) Result (ppm SO2) Result (% CO2) Result

Messer MG Industries Low 50.0 Pass 50.1 Pass 5.05 PassMesser MG Industries Mid 398 Pass 501 Pass 12.1 PassMesser MG Industries High 888 Pass 1004 Pass 18.2 Pass

Messer MG Industries (Spec Air Specialty Gas) Low 50.0 Pass 49.3 Pass 5.07 PassMesser MG Industries (Spec Air Specialty Gas) Mid 403 Pass 496 Pass 12.1 PassMesser MG Industries (Spec Air Specialty Gas) High 894 Pass 1004 Pass 18.3 Pass

National Specialty Gases (a) Low 46.2 Fail 51.8 Fail 4.90 PassNational Specialty Gases Mid 398 Pass 500 Pass 12.0 PassNational Specialty Gases (a) High 930 Pass 991 Pass 17.8 Fail

Praxair Low 51.2 Pass 50.0 Pass 5.00 PassPraxair Mid 406 Pass 509 Pass 12.18 PassPraxair (a) High 914 Pass 999 Pass 17.59 Fail

Scott Specialty Gases Low 50.0 Pass 50.4 Pass 5.04 PassScott Specialty Gases Mid 402 Pass 503 Pass 12.10 PassScott Specialty Gases High 911 Pass 1011 Pass 17.97 Pass

Scott-Marrin In. Low 50.8 Pass 50.9 Pass 5.11 PassScott-Marrin In. Mid 397 Pass 504 Pass 12.02 PassScott-Marrin In. High 886 Pass 997 Pass 17.92 Pass

Spectra Gases Inc. Low 50.1 Pass 50.2 Pass 5.02 PassSpectra Gases Inc. Mid 405 Pass 495 Pass 12.03 PassSpectra Gases Inc. High 923 Pass 988 Pass 18.07 Pass

Gas Vendor

NO SO2 CO2

Results Overall failure rate: 14 of 126 analyses (11%) 57% of vendors failed SO2: Worst tag value ~2.5% high NO: Worst tag value ~8% low CO2: Worst tag value ~4.9% high All 42 cylinders met the Protocol Procedure

documentation requirements

- - -- - -3/140/143/140/14- - -3/14- - -High

0/141/140/140/140/140/142/143/142/14Mid

1/141/141/141/141/146/144/144/146/14Low

BothFTIRNDIRBothFTIRUVBothFTIRUV

CO2 AnalysesSO2 AnalysesNO Analyses

EPA Protocol Gases not meeting Acceptance Criterion

Percent Failure Rate by Vendor Technology

NO SO2 CO2

Chem NDIR FTIR NDIR UV FTIR NDIR FTIR TCD

14.3 16.7 27.8 0.0 0.0 6.7 4.2 20.0 0.0

Lessons Learned Detailed standard operating procedures for

analyzing single and multicomponent mixtures are needed in EPA’s Protocol Procedures, especially for FTIR

First ensure lab can correctly analyze single component cylinders

Then check for interferences by measuring a multicomponent cylinder simultaneously with analyzers for each component gas

Use an SRM or NTRM to get reference spectrum for FTIR measurements

Audits Can Be Effective

Failure Rate on Cal Gas Blind Audits

0.00

10.00

20.00

30.00

40.00

1992 1993 1994 1995 1996 2003

Audit Program Issues

Scope Stringency Structure

Options - Scope

Part 75 only All source-level programs, e.g.,

Part 75, NSPS, SIP, NSR All source and ambient-level

programs

Options - Stringency

Work with vendors to fix problems

Work with vendors and post audit results on web sites

Formal gas vendor certification program

Options - Structure Spin-off to 3rd party (A2LA, NVLAP, NSF,

etc.) to purchase and analyze cylinders (set up fee-based system) with EPA oversight

Through EPA task order, contractor purchases and analyzes cylinders from major suppliers (EPA used to do this)

Other (NELAC, gas vendor-developed mechanism, NIST, EPA lab, etc.)

Initial Recommendations

ScopeAll source and ambient-level programsStringencyWork with vendors; post audit resultsStructureSet up fee-based system to purchase and

analyzecylinders using 3rd party with EPA oversight; orpossibly use gas vendor-developed mechanism

Example 3rd Parties for Spin Off

American Association for Laboratory Accreditation (A2LA)

National Voluntary Laboratory Accreditation Program (NVLAP)

National Sanitation Foundation (NSF)

Next Steps

Get more feedback from gas vendors and other interested parties

For a Copy of Presentation

www.epa.gov/airmarkets, click on

“Recent Additions” near top left corner or

John SchakenbachPhone: 202-343-9158

schakenbach.john@epa.gov