2003/2004 AUDITS OF EPA TRACEABILITY PROTOCOL CYLINDER GASES

Contract No. 68-W-03-033

Work Assignments 0-7 and 1-7

Prepared for 

John Schakenbach (6204J)

U.S. Environmental Protection Agency

1310 L Street, NW

Washington, DC 20005

Prepared by

Scott Shanklin

The Cadmus Group, Inc.

6330 Quadrangle Drive, Suite 180

Chapel Hill, NC 27517

November 22, 2004

November 22, 2004 iii

NOTICE AND DISCLAIMER

The U.S. Environmental Protection Agency through the Clean Air Markets Division in the Office of

Atmospheric Programs funded and managed the preparation of this document under Contract No. 68-W03-033. The mention of trade names or commercial products does not constitute endorsement or

recommendation or use by either the U.S. Environmental Protection Agency or The Cadmus Group, Inc.,

of the product or manufacturer.

November 22, 2004 v

TABLE OF CONTENTS

Notice and Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

Acronyms and Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

i

1.0 INTRODUCTION ............................................................... 1

2.0 SELECTION OF GAS VENDORS .................................................. 2

3.0 PURCHASE OF EPA TRACEABILITY PROTOCOL GASES . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

4.0 ANALYTICAL PROCEDURES .................................................... 4

4.1 MACTEC ANALYTICAL PROCEDURES ............................................. 4

4.2 SPECTRAL INSIGHTS ANALYTICAL PROCEDURES ..................................... 6

5.0 RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5.1 DOCUMENTATION ............................................................. 9

5.2 GAS ANALYSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

6.0 CONSIDERATIONS FOR FUTURE PROTOCOL GAS AUDITS . . . . . . . . . . . . . . . . . . . . . . . . 16

APPENDIX A. GAS MEASUREMENT DATA AND COMPARISONS
November 22, 2004 vi

TABLES

1. U.S. Commercial Manufacturers of EPA Traceability Protocol Gases (as of 2004) .............. 3

2. Gases Purchased for the 2003/2004 Audit .............................................. 3

3. Reference Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4. Spectral Insights’ FTIR Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

5. Vendor Cylinder Gas Certification Using EPA Traceability Protocol ......................... 9

6. NO Component Analysis Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

7. SO2 Component Analysis Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

8. CO2 Component Analysis Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

FIGURES

1. MACTEC’s assay apparatus ......................................................... 5

2. Spectral Insights’ assay apparatus ..................................................... 8
November 22, 2004 vii

ACRONYMS AND ABBREVIATIONS

ASTM American Society for Testing and Materials

CAMD Clean Air Markets Division

CEMS continuous emission monitoring system

CFR Code of Federal Regulations

CO2 carbon dioxide

CO carbon monoxide

DAS data acquisition system

EPA U.S. Environmental Protection Agency

FTIR Fourier Transform Infrared

GC gas chromatograph/chromatography

GMIS Gas Manufacturer’s Intermediate Standard

ID identification

mm Hg millimeters of mercury

N2 nitrogen gas

NIST National Institute of Standards and Technology

NDIR nondispersive infrared detection

NO Nitrous oxides

NOX nitrogen oxides

NTRM NIST-traceable reference materials

% percent

PC personal computer

ppm parts per million

QA quality assurance

QC quality control

RTD resistive temperature device

SRM Standard Reference Materials

UHP ultra high pure

UV ultraviolet
November 22, 2004 1

§ 2.1.4: Certificate of Analysis

cylinder ID

certified concentration of analyte

balance gas

cylinder pressure

assay/certification date

certification expiration date

identification of reference standards

used in the assay

protocol statement

analytical method used in the assay

name and signature of analyst and

laboratory name

if applicable, statement that certified

value has been corrected for analytical

interferences

estimate of total uncertainty

§ 2.1.5: Certification Label

cylinder ID number

certified concentration of analyte

balance gas

cylinder pressure

certification and expiration dates

protocol statement

name of certifying laboratory

1.0 INTRODUCTION

The U.S. Environmental Protection Agency’s (EPA) Clean Air Markets Division (CAMD) is

responsible for implementing the Part 75 emission monitoring acid rain control regulations promulgated

on January 11, 1993 and revised on May 1, 2002. An essential component of Part 75 is the certification

and ongoing quality assurance (QA) activities for continuous emission monitoring systems (CEMS).

Under Part 75, calibration gases are used to conduct daily calibration error determinations and quarterly

linearity tests. Calibration gases are also used to calibrate EPA test method equipment, which, in turn, is

used to assess the measurement accuracy of installed CEMS that regulated sources use to determine

emissions. To conduct these QA activities, accurate calibration gases are required.

Part 75 regulations require that the certified concentrations for calibration gases be traceable to

National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs) according

to the requirements of “EPA Traceability Protocol for Assay and Certification of Gaseous Calibration

Standards” (EPA Traceability Protocol), September 1997 (EPA-600/R-97/121). The protocol was

originally published in 1978 and has been revised several times, most recently in 1997. EPA Traceability

Protocol gases deviate from the certified value by no more than ± 2 percent, and the concentrations are

stable for 12 to 36 months, depending on the components of the gas blend.

The EPA Traceability Protocol specifies two types of documentation that must accompany a

calibration gas cylinder: (1) a certification of analysis (§ 2.1.4 Certification Documentation), which may

be mailed separately or attached to the cylinder; and (2) a

certification tag (§ 2.1.5 Certification Label), which must be

attached to the valve under the valve cap.

Section 2.1.10 of the

EPA Traceability

Protocol states that EPA

will periodically assess

the accuracy of

calibration gases and

publish the results.

Between 1978 and 1996,

EPA’s Office of Research

and Development

conducted several

performance audits of

calibration gases from

various manufacturers. These audits provided a quality check

for gas vendors and connected users with good gas vendors. In

the most recent five years of audits, the failure rate of the

calibration gases declined from about 27 percent in 1992 to

5 percent in 1996. Because of budgetary constraints, audits of

calibration gases have not been performed since 1996, and the

activity was transferred to EPA’s Office of Air and Radiation.

In 2003, EPA’s CAMD conducted an audit to evaluate the accuracy of the specialty gas

manufacturers’ reported concentrations for three-component cylinder gas blends. EPA procured tri-blend

cylinder gases certified according to EPA’s Traceability Protocol from 14 gas manufacturers, checked the

accuracy of the manufacturers’ certifications of concentration, and examined the accompanying

documentation. The reported concentrations of the three three-component cylinder gas blends (each in a
November 22, 2004 2

Gas Composition of Audited Cylinders

Concentration

Level 

Sulfur dioxide

– SO2 (ppm)

Nitric oxide

– NO (ppm)

Carbon dioxide

– CO2 (%)

Low 50 50 5

Mid 500 400 12

High 1000 900 18

balance of nitrogen) were verified. Two laboratories

assayed the cylinder gases using different analytical

techniques. MACTEC used standard gas analyzers,

and Spectral Insights used a Fourier transform

infrared (FTIR) spectrometer. Both laboratories used

“Procedure G1: Assay and Certification of a

Compressed Gas Standard Calibration Without

Dilution” (EPA-600/R-97/121).

The standard for comparison is the relative difference between the vendor-certified values and EPA’s

laboratory results, which must be within ± 2.0 percent. Part 75, Appendix A, Section 5.1.4 requires

calibration gases to be within 2.0 percent of the concentration specified on the certification label. The ±

2.0 percent limit accommodates the ±1 percent uncertainty in the NIST SRM concentrations and the ±

1 percent uncertainty in the balance of the measurement system used to produce EPA Traceability

Protocol gases. As such, if the difference between EPA’s value and the gas vendor’s value differs by ±

2.0 percent or less, the two values do not differ statistically. 

Vendors were notified in writing if any of the concentrations in their gases differed by more than 

± 2.0 percent from those determined by both analytical laboratories, or if their documentation was

incomplete. The high-level NO and high-level CO2 gases, however, were compared using data from only

one of the two analytical laboratories because of an unresolved NOx analyzer issue, and the high-level

CO2 SRM was emptied before the FTIR analyses were performed.

The audit results are posted on two EPA Web sites: www.epa.gov/airmarkets/monitoring and

www.epa.gov/ttn/emc/new. (Scroll to “EPA 2003 Blind Audit of Protocol Calibration Gases for CEMS”

after accessing the sites.) Posting on the Web enables users of the EPA Traceability Protocol gases to

readily judge how well the gas manufacturers’ products performed in the audit.

2.0 SELECTION OF GAS VENDORS

At the beginning of this project in support of CAMD, The Cadmus Group, Inc. conducted a study to

identify U.S. commercial gas manufacturers which produce and market gas standards that are prepared

and analyzed according to EPA’s Traceability Protocol. Cadmus’ search of the Air and Waste

Management Web site, the Internet, and previous EPA audit publications indicated that 25 gas

manufacturers marketed EPA Traceability Protocol gases. Followup by telephone confirmed that 11 of

these specialty gas companies produce EPA Protocol gas standards, while the others were only

distributors of gas products. These producers are listed in Table 1, along with the supplier, and the

laboratory location where the gas concentrations are certified.

Not listed in Table 1 are a few vendors that were included in earlier EPA audits, but have since been

acquired by other companies. For example, AIRCO is now BOC Gases and Airgas; Alphagaz is now Air

Liquide; and Liquid Carbonic is now Praxair. The latest transaction occurred in July 2004 after

completing the audit when BOC sold their U.S. packaged gas business (which included EPA Protocol

gases) to Airgas and National Welders.
November 22, 2004 3

Table 1. U.S. Commercial Producers of EPA Traceability Protocol Gases (as of 2004)

Gas Producer Supplier Laboratory Location

Air Liquide A-L Specialty Gases La Porte, TX

Airgas Airgas Southwest Specialty Gases Mobile, AL

Airgas NCN Specialty Gases Los Angeles, CA

Airgas South Specialty Gases Mobile, AL

BOC Gases MWSC High Purity Gases Riverton, NJ

AGA Gas, Inc. AGA Gas, Inc. Maumee, OH

Matheson Tri-Gas Matheson Tri-Gas Twinsburg, OH

Messer MG Industries MG Industries – Richmond, VA Morrisville, PA

Spec Air Specialty Gases Morrisville, PA

National Specialty Gases National Welders Durham, NC

Praxair Praxair Los Angeles, CA

Scott Specialty Gases Scott Specialty Gases Plumsteadville, PA

Scott-Marrin, Inc. Scott-Marrin, Inc. Riverside, CA

Spectra Gases, Inc. Spectra Gases, Inc. Alpha, NJ

3.0 PURCHASE OF EPA TRACEABILITY PROTOCOL GASES

Cadmus arranged for third-party purchases of EPA Traceability Protocol gases from the 14 vendors.

Cadmus selected ARCADIS to purchase the gases, receive the gas cylinders at their facility in Research

Triangle Park, North Carolina, and transfer the cylinders to the primary laboratory for analysis. Cadmus

ordered the gases, which ranged in price from $288 to $1,384 per cylinder, in December 2002 and

January 2003. The vendor-reported concentrations of the purchased gases are presented in Table 2.

Table 2. Gases Purchased for the 2003/2004 Audit

Gas Vendor

Conc.

Range Cylinder ID

Vendor-Reported Gas Concentrations

NO (ppm) SO2 (ppm) CO2 (%)

Air Liquide Low

Mid

High

CC66623

CC92259

CC60899

54.0 ± 0.8 ppm

401 ± 5 ppm

911 ± 10 ppm

47.5 ± 0.8 ppm

499 ± 4 ppm

981 ± 9 ppm

4.97 ± 0.06 % CO2

12.1 ± 0.1 % CO2

17.7 ± 0.2 % CO2

Airgas Southwest Low

Mid

High

CC148939

CC48489

CC125139

48.90 ± 1 %

406.0 ± 1 %

900.0 ± 1 %

47.73 ± 1 %

496.8 ± 1 %

994.6 ± 1 %

5.01 ± 1 %

12.00 ± 1 %

17.99 ± 1 %

Airgas NCN Low

Mid

High

CC152482

CC60532

CC137805

51.4 ± 1 %

388 ± 1 %

845 ± 1 %

50.4 ± 1 %

500 ± 1 %

1000 ± 1 %

5.01 ± 1 %

12.0 ± 1 %

18.0 ± 1 %

Airgas South Low

Mid

High

SG9151036

CC156246

SG9170299

50.05 ± 1 %

397.5 ± 1 %

900.0 ± 1 %

50.23 ± 1 %

502.8 ± 1 %

998.8 ± 1 %

5.041 ± 1 %

12.00 ± 1 %

18.07 ± 1 %

BOC Gases Low

Mid

High

CC24569

XC034007B

XC034030B

49.8 ± 1 %

407.8 ± 1 %

900 ± 1 %

50.9 ± 1 %

500.4 ± 1 %

1000 ± 1 %

5.00 ± 1 %

11.98 ± 1 %

18.02 ± 1 %

AGA Low

Mid

High

CC35129

CC91994

CC22914

50.4 ± 0.5 ppm

396 ± 4 ppm

904 ± 9 ppm

48.7 ± 0.5 ppm

466 ± 5 ppm

956 ± 10 ppm

5.20 ± 0.5 % CO2

12.5 ± 0.1 % CO2

18.3 ± 0.2 % CO2

Matheson

Tri-Gas

Low

Mid

High

SX23321

SX31387

SX16476

48.9 ± 0.4 ppm

410 ± 1 ppm

904 ± 9 ppm

49.5 ± 0.4 ppm

504 ± 5 ppm

988 ± 9 ppm

5.23 ± 0.05 % CO2

12.2 ± 0.1 % CO2

17.9 ± 0.1 % CO2

Messer MG

Industries

Low

Mid

High

CC6166

CC11490

CC27833

50.0 ± 0.128 ppm

398 ± 1.28 ppm

888 ± 2.99 ppm

50.1 ± 0.507 ppm

501 ± 1.82 ppm

1004 ± 3.1 ppm

5.05 ± 0.0444 % CO2

12.1 ± 0.0501 % CO2

18.2 ± 0.0501 % CO2

Messer MG

Industries

(Spec Air Gases)

Low

Mid

High

CC9159

CC17527

CC2193

50.0 ± 0.131 ppm

403 ± 1.28 ppm

894 ± 2.99 ppm

49.3 ± 0.506 ppm

496 ± 1.82 ppm

1004 ± 3.1 ppm

5.07 ± 0.0444 % CO2

12.1 ± 0.0501 % CO2

18.3 ± 0.0501 % CO2
Table 2. Gases Purchased for the 2003/2004 Audit

Gas Vendor

Conc.

Range Cylinder ID

Vendor-Reported Gas Concentrations

NO (ppm) SO2 (ppm) CO2 (%)

1 MACTEC Federal Programs, Inc. 2004. A Survey of Commercially Available Compressed Gas Standards –

Final Report. June, prepared for The Cadmus Group, Inc.

November 22, 2004 4

Gas Analyzers Used by MACTEC

Model Analyte Measurement Principle

Western Research

Model 721M

SO2 ultraviolet (UV)

absorption

AMETEK Model 922 NOx UV detection

California Analytical

Model 3300A

CO2 nondispersive infrared

(NDIR) detection

National Specialty

Gases

Low

Mid

High

CC129710

SG9151344BAL

CC109625

46.2 ± 1 %

398 ± 1 %

930 ± 1 %

51.8 ± 1 %

500 ± 1 %

991 ± 1 %

4.90 ± 1 %

12.0 ± 1 %

17.8 ± 1 %

Praxair Low

Mid

High

CC134131

CC104955

SA13826

51.2 ± 1 %

406 ± 1 %

914 ± 1 %

50.0 ± 1 %

509 ± 1 %

999 ± 1 %

5.00 ± 1 %

12.18 ± 1 %

17.59 ± 1 %

Scott Specialty

Gases

Low

Mid

High

ALM017308

ALM037407

ALM039857

50.0 ± 1 %

402 ± 1 %

911 ± 1 %

50.4 ± 1 %

503 ± 1 %

1011 ± 1 %

5.04 ± 1 %

12.10 ± 1 %

17.97 ± 1 %

Scott-Marrin, Inc. Low

Mid

High

CC103753

CC122611

CC12406

50.8 ± 0.3 ppm

397 ± 2 ppm

886 ± 5 ppm

50.9 ± 0.6 ppm

504 ± 5 ppm

997 ± 10 ppm

5.11 ± 0.05 % CO2

12.02 ± 0.02 % CO2

17.92 ± 0.05 % CO2

Spectra Gases, Inc. Low

Mid

High

CC107089

CC94719

CC88654

50.1 ± 1 %

405 ± 1 %

923 ± 1 %

50.2 ± 1 %

495 ± 1 %

988 ± 1 %

5.02 ± 1 %

12.03 ± 1 %

18.07 ± 1 %

Reference standards were either SRMs purchased from NIST or NIST-traceable reference materials

(NTRMs) purchased from BOC Gases that were certified by NIST. These standards are listed in Table 3.

Table 3. Reference Standards

Component Certification Vendor

Sample

ID

Cylinder

ID

SRM Sample

 No.

Concentration

(in N2 balance)

CO2 NTRM B NTRM 81674x XC018106B – 4.811 % CO2

SRM S SRM 1674b 014632 7-F-43 6.876 % CO2

SRM S SRM 1674b 014550 7-F-52 6.876 % CO2

NTRM B NTRM 82745x XC018675B – 19.69 % CO2

NO SRM P SRM 1683b FF17312 45-T-37 46.7 ppm NO

SRM S SRM 2735 0014283 141-B-40 781.8 ppm NO

SRM S SRM 2630 09911 46-D-24 1476.2 ppm NO

SO2 SRM S SRM 1694a 010608 95-G-38 97.6 ppm SO2

NTRM B NTRM 81661 XC006221B – 486.0 ppm SO2

SRM P SRM 1662a FF17174 93-G-26 973.3 ppm SO2

NTRM B NTRM 81662 XC006240B – 997.0 ppm SO2

Vendor code: B – BOC Gases; S – Scott Specialty Gases; P – Praxair

4.0 ANALYTICAL PROCEDURES

4.1 MACTEC ANALYTICAL PROCEDURES

MACTEC performed the cylinder assays using

“Procedure G1: Assay and Certification of a

Compressed Gas Standard Calibration Without

Dilution” (EPA-600/R-97/121).1

 Analyses of the

compressed gas standards were performed using

three commercially available gas analyzers.

The SO2, NOx, and CO2 analyzer responses were

recorded using strip-chart recorders and a PC-based
November 22, 2004 5

UHP N2

Zero

CO2

Reference

NOx

Reference

SO2

Reference

Candidate

Reference

Candidate

Standard

Candidate

Standard

Pressure

Regulator

Gas

Flow 

Selector

Pressure

Gauge AMETEK

Model 922

NOx Analyzer

Western Research

Model 721M

SO2 Analyzer

CAI Model 100

CO2 Analyzer

Analog

Digital

Converter

Data

Acquisition

PC

Vent

Figure 1. MACTEC’s assay apparatus.

data acquisition system (DAS)—Workbench for Windows. The DAS polled each analyzer at 2-second

intervals. The data were reduced to 1-minute averages, and the average response of each analyzer was

calculated. Figure 1 is a schematic diagram of the equipment set up.

Analyzer multi-point calibrations were conducted at the start of each assay session. Each analyzer

was calibrated using SRMs or NTRMs according to the procedures outlined in Section 2.1.7 of EPA’s

Protocol. Calibration standards were introduced into the analyzers using a calibration flow panel. The use

of the flow panel ensured that gases were introduced into each analyzer under consistent flow and

pressure conditions. Intermediate calibration points were generated using a dilution panel (this step was

the only one during which any gas standard was diluted). Using the analyzer responses, the estimated

calibration line and the upper and lower confidence bands corresponding to 95-percent uncertainty were

plotted.

Forty-two candidate standards were assayed during nine assay sessions over four days. Before the

start of each day’s assays, a zero gas and an upscale reference standard were introduced into each

analyzer to assess zero drift and upscale drift relative to the initial calibration curve. If the response of any

analyzer to either reference standard differed by more than five percent from the multi-point calibration, a

new multi-point calibration curve was generated. All daily drift checks showed that analyzer drift was

within acceptable limits.

During each assay session, candidate gases, reference gases, and a zero gas were introduced into the

analyzers one at a time. Instantaneous responses were recorded on data forms as a check to ensure that the

values reported by the DAS corresponded with actual analyzer responses. At the conclusion of each day,

the zero and upscale gas standard were introduced into the analyzers as a final check of instrument drift.

Actual concentrations of each gas component were calculated using MS Excel spreadsheets

developed by Research Triangle Institute. The true concentration of each component was calculated based
2 Spectral Insights, Inc. 2004. FTIR Measurements of Candidate EPA Protocol Standards – Final Report. June,

prepared for The Cadmus Group, Inc.

November 22, 2004 6

on the analyzer response, the multi-point calibration curve, and the daily zero and upscale calibration drift

results.

MACTEC performed the NO analyses twice, first using a chemiluminescence analyzer (API Model

200AH) and then using the AMETEK UV analyzer. The API NO measurements were low relative to the

cylinder tag values because of CO2 quenching. Several unsuccessful attempts were made to quantify the

CO2 interference effects and to develop a correction that could be applied to the data. Consequently, the

NO measurement data obtained using the API chemiluminescence analyzer were discarded, and the NO

analyses were repeated using the AMETEK UV analyzer.

With the AMETEK Model 922 UV analyzer, an interference between the NO and SO2 measurement

channels occurs. The analyzer measures both NO and SO2 concentrations and automatically corrects the

NO measurement data for the SO2 interference. Although AMETEK optimized the analyzer’s operation

for analyzing the gas blends and concentration levels before providing it for use in the audit, the data

obtained during MACTEC’s analyses showed a low NO bias at the 900-ppm level. The analyzer was

therefore returned to AMETEK for a thorough performance evaluation.

To conduct the interference check on the Model 922 analyzer, AMETEK used EPA Traceability

Protocol gases and an Environics gas divider (with nitrogen as the diluent) to obtain the gas blends of SO2

and NO. The gas blending and injection routine was automated. Each gas blend was run through the

analyzer for 4 minutes to obtain stable readings, and a DAS averaged the readings over the next 2

minutes. The system then switched to the next gas (or blend). Two repetitions were performed.

AMETEK’s results confirmed a negative cross-interference of SO2 onto the NO channel. They also

found the high-concentration blend readings were about 3 percent low at the 900-ppm NO level.

Although AMETEK derived a correction to apply to MACTEC’s NO data, the bias was not corrected.

AMETEK noted that the analyzer had a 40-cm path length cell installed, which they would not spec for

ranges above 500 ppm. Typically, an 80-cm cell is used for measurement ranges up to 250 ppm, and a 10-

cm path length cell is used for ranges from 250 – 2000 ppm. Given that the audited gas concentrations

ranged from 50 – 900 ppm, however, AMETEK provided the analyzer with a 40-cm cell knowing that

accuracy at both ends of the range might be affected.

The high-level NO data from the AMETEK UV analyzer were deemed questionable, because the

negative bias was concluded to be likely due to the analyzer set up. As a result, EPA excluded these

results and used only FTIR data obtained by Spectral Insights (see Section 4.2) for the high-level NO

cylinder evaluations.

4.2 SPECTRAL INSIGHTS ANALYTICAL PROCEDURES

To confirm MACTEC’s results, the EPA Traceability Protocol gas standards were analyzed by

Spectral Insights using an FTIR analyzer and “Procedure G1: Assay and Certification of a Compressed

Gas Standard Calibration Without Dilution” (EPA-600/R-97/121).2

 Sampling was conducted in

accordance with EPA’s Traceability Protocol. Analyses were performed using a Nicolet Nexus 760 FTIR

spectrometer.

Table 4 provides information on Spectral Insight’s FTIR instrumentation. All sample-wetted

components were made of one of the following materials: Stainless steel, polytetrafluoroethylene (i.e.,

TeflonTM), glass, gold, or nickel-coated aluminum. Figure 2 is a schematic diagram of the apparatus.

Spectral Insights did not provide details on the spectral regions or any algorithms used in the FTIR

analysis due to proprietary concerns.
November 22, 2004 7

Table 4. Spectral Insights’ FTIR Instrumentation

Component/Parameter Specification

Measurement System Spectral Insights Series 2000

Spectral Resolution 0.5 wave number (up to 0.125 wave number)

Spectral Range 600 – 7900 wave numbers 

Optical Path Length 3.12 meters (adjustable to nominal 1 to 10 meters)

IR Detector MCT operated at 77 Kelvin

Operating Pressure, Temperature Nominal 760 mm Hg, 25 °C

Cell Pressure Thin-film, 0.1 mm Hg resolution, range: 0 – 1550 mm Hg

Vendor-stated accuracy: less than ± 0.25 % full scale

Cell Temperature RTD, 0.1°C resolution, range 0 – 200 °C

Spectral Insights used the following measurement procedure for an analysis run for a given candidate

standard range:

1. Measure appropriate SRM or NTRM standard for each target analyte and install as reference

spectrum for respective analyte.

2. Use a random number sequence generator to determine measurement sequence of candidate,

SRM/NTRM, and zero gases.

3. Vent sample gas manifold and flush and vent manifold with next sample gas at least three times.

Ensure that only one source gas valve in manifold is open at any time.

4. Evacuate FTIR sample cell to less than 1 mm Hg absolute pressure and fill with candidate

standard gas at or slightly above atmospheric pressure (normally 760 mm Hg).

5. Repeat Step 4 above two more times.

6. Flow candidate (or zero) gas standard at rate of three times cell volume per minute for two

minutes (i.e., flow six cell volumes through cell). Isolate sample in cell.

7. Measure 256 spectral scans (approximately seven minutes). Concurrently measure sample gas

temperature and pressure.

8. Perform spectral analysis and record result.

9. Repeat with next standard in sequence starting at Step 3.
November 22, 2004 8

Candidate, Zero, SRM or NTRM 

Gas Standards

FTIR Spectrometer Cell

Vacuum Pump

Selector Valve

Isolation Valves

Vent

P

T

Computer

Transducers

Check 

Valves

Toggle Valves

Vent

Gas Manifold/Regulator

Manifold Vent Valve

Vent

Figure 2. Spectral Insights’ assay apparatus.

No high-level CO2 SRM or NTRM was supplied to Spectral Insights because the gas standard was

emptied during MACTEC’s analyses. Therefore, Spectral Insights blended a CO2 standard directly in the

FTIR gas cell to generate a high-range reference spectrum. Blending was accomplished by adding 153.2

mm Hg of 99.99 percent purity CO2 to the cell and filling to 760.0 mm Hg with UHP nitrogen. After

correction for CO2 compressibility (less than 0.1 percent correction at 153.2 mm Hg partial pressure), the

calculated concentration was determined to be 20.16 molar percent. A mid-level CO2 standard was also

prepared in the same way to check the mid-level response (nominal 12 percent CO2) of the measurement

system.

Because the principle of operation for FTIR spectrometers differs from that for gas analyzers, some of

the procedures in the EPA Traceability Protocol are not applicable. For example, FTIR spectrometers do

not have conventional “zero” and “span” controls. Calibration is conducted by generating “reference”

spectra for each analyte at precisely known conditions (i.e., pressure, temperature, optical path length, and

concentration) using zero gas (nitrogen) and the SRMs or NTRMs. The spectra of the candidate standards

were directly compared to the respective reference spectrum using multivariate least squares, a standard

spectral analysis technique. Because this procedure is carried out for each analysis run, there is no drift.

Spectral bands that are too strong in intensity can exhibit non-linearity, which can be predicted (via

simulation) and corrected. If the concentration of the reference spectrum is close to those of the candidate

standards, and a strong spectral band is used, non-linear corrections are usually not required. In this test

program, however, all spectral bands chosen showed linear responses for all reference spectra used in the

measurement range for the candidate standards.
November 22, 2004 9

5.0 RESULTS

5.1 DOCUMENTATION

The documentation that accompanied each EPA Traceability Protocol gas cylinder was complete and

conformed to the requirements in the Protocol. Documentation included a Certificate of Analysis in

accordance with § 2.1.4 of the Protocol, and a Certification Label, in accordance with § 2.1.5 of the

Protocol. The analytical technique and reference standards used by the gas vendors are listed in Table 5.

Analytical techniques used most commonly for NO certification were FTIR and chemiluminesence;

two vendors used nondispersive infrared (NDIR) detection. For SO2 certification, five vendors used FTIR,

seven used NDIR, one vendor used UV, and one used UV for the low-level concentration and NDIR for

the mid- and high-level concentrations. Five vendors certified the CO2 standards using FTIR, eight used

NDIR, and one used gas chromatography (GC).

Most vendors used Gas Manufacturers’ Intermediate standards (GMIS) or NTRMs to certify their gas

concentrations. A few vendors used SRMs.

Table 5. Vendor Cylinder Gas Certification Using EPA Traceability Protocol

Gas Vendor

Gas

Conc.

Range

NO Certification SO2 Certification CO2 Certification

Analytical

Technique

Reference

Standards

Analytical

Technique

Reference

Standards

Analytical

Technique

Reference

Standards

Air Liquide Low FTIR GMIS FTIR GMIS FTIR GMIS

Mid FTIR GMIS FTIR GMIS FTIR GMIS

High FTIR GMIS FTIR GMIS FTIR NTRM

Airgas Southwest Specialty

Gases

Low Chem NTRM NDIR NTRM NDIR NTRM

Mid Chem NTRM NDIR NTRM NDIR NTRM

High Chem NTRM NDIR NTRM NDIR NTRM

Airgas NCN Specialty Gases Low NDIR NTRM NDIR GMIS NDIR NTRM

Mid NDIR NTRM NDIR NTRM NDIR NTRM

High NDIR NTRM NDIR NTRM NDIR NTRM

Airgas South Specialty

Gases

Low Chem GMIS NDIR NTRM NDIR NTRM

Mid Chem NTRM NDIR NTRM NDIR NTRM

High Chem NTRM NDIR NTRM NDIR NTRM

BOC Gases Low FTIR SRM FTIR SRM FTIR NTRM

Mid FTIR SRM FTIR NTRM FTIR NTRM

High FTIR SRM FTIR NTRM FTIR NTRM

AGA

(Linde Gas Group)

Low Chem GMIS NDIR GMIS NDIR NTRM/GMIS

Mid Chem GMIS NDIR GMIS NDIR NTRM/GMIS

High Chem GMIS NDIR GMIS NDIR NTRM/GMIS

Matheson Tri-Gas Low FTIR SRM FTIR SRM FTIR SRM

Mid FTIR SRM FTIR SRM FTIR SRM

High FTIR SRM FTIR SRM FTIR SRM

Messer MG Industries Low Chem GMIS NDIR GMIS NDIR GMIS

Mid Chem GMIS NDIR GMIS NDIR GMIS

High Chem GMIS NDIR GMIS NDIR GMIS

Messer MG Industries

(Spec Air Gases)

Low Chem GMIS NDIR GMIS NDIR GMIS

Mid Chem GMIS NDIR GMIS NDIR GMIS

High Chem GMIS NDIR GMIS NDIR GMIS

National Specialty Gases Low FTIR GMIS FTIR GMIS FTIR GMIS

Mid FTIR GMIS FTIR GMIS FTIR GMIS

High FTIR GMIS FTIR GMIS FTIR GMIS
Table 5. Vendor Cylinder Gas Certification Using EPA Traceability Protocol

Gas Vendor

Gas

Conc.

Range

NO Certification SO2 Certification CO2 Certification

Analytical

Technique

Reference

Standards

Analytical

Technique

Reference

Standards

Analytical

Technique

Reference

Standards

November 22, 2004 10

Praxair Low Chem GMIS UV GMIS NDIR GMIS

Mid NDIR GMIS NDIR GMIS NDIR GMIS

High NDIR GMIS NDIR GMIS NDIR GMIS

Scott Specialty Gases Low FTIR NTRM FTIR NTRM FTIR NTRM

Mid FTIR NTRM FTIR NTRM FTIR NTRM

High FTIR NTRM FTIR NTRM FTIR NTRM

Scott-Marrin, Inc. Low Chem GMIS UV GMIS GC GMIS

Mid Chem GMIS UV GMIS GC GMIS

High Chem GMIS UV GMIS GC GMIS

Spectra Gases, Inc. Low Chem NTRM NDIR NTRM NDIR GMIS

Mid FTIR NTRM NDIR GMIS NDIR NTRM

High FTIR NTRM NDIR GMIS NDIR NTRM

FTIR – Fourier transform infrared

GMIS – Gas Manufacturer’s Intermediate Standard

NTRM – NIST traceable reference material

Chem – Chemiluminescence

NDIR – Non-dispersive infrared

SRM – Standard reference material

UV – Ultraviolet

GC – Gas chromatography

5.2 GAS ANALYSES

Tables 6, 7, and 8 on pages 12 – 16 present the NO, SO2, and CO2 concentrations, respectively,

determined by the manufacturers and by MACTEC and Spectral Insights, along with the percent

differences between the concentration determinations. The percent differences were computed relative to

the EPA-determined values. More detailed audit data are presented in Appendix A, Tables A-1, A-2, and

A-3. The MACTEC measurement data are presented in Table A-4, and the Spectral Insights’

measurement data are presented in Table A-5.

The results differed by less than 2.0 percent for 33 of the 42 cylinders for NO, 41 of the 42 cylinders

for SO2, and 38 of 42 cylinders for CO2.

In April 2004, the manufacturers were notified of their audit results in writing without revealing the

actual audit concentrations. The manufacturers whose gas concentrations differed by more than ±

2.0 percent from both EPA-determined concentrations (i.e., MACTEC and Spectral Insights results) were

offered the opportunity to reanalyze their gases and submit the new results to EPA for inclusion in this

report and in the report posted on the EPA Web sites. Cadmus discussed the audit procedures (to the

extent that FTIR information was made available by the Spectral Insights) with various gas vendors and

responded to their questions and comments. Most vendors stated that they reviewed all of their laboratory

routines and had also re-checked the laboratory documentation for their gases. 

Six gas vendors (Air Liquide, Airgas, Praxair, Matheson, BOC Gases, and National Specialty Gases)

reanalyzed their cylinders to investigate the discrepancies shown by the MACTEC or Spectral Insights

results. All reanalyzed results submitted to EPA were within ± 2.0 percent of the corresponding EPA

value.

In most cases, the reanalyzed concentration value was within ±2 percent of the original certified tag

value, which is the specification for EPA Traceability Protocol gases, and also was within ± 2 percent of

the EPA-determined values. Of the few concentrations that changed by more than ± 2 percent, three were

at the low-level NO, one was at the low-level CO2, and one at the high-level CO2.

One point to consider is that the 2-percent criterion must account for the analytical uncertainty

associated with both the gas vendor’s and auditor’s measurements. If the analyses have an uncertainty of

± 2 percent and the results are in opposite directions, the two measurements can differ by up to 4 percent.
November 22, 2004 11

If the two measurements are made using the same analytical technique, the likelihood of this scenario

would be decreased. Regardless, the EPA-determined value is deemed to be the “true” for the purposes of

the cylinder gas audit, and considering alternatives to the specification is beyond the scope of this study.

The EPA Traceability Protocol is a general analytical procedure, which does not allow or disallow

specific analytical procedures to measure specific gas mixtures—the laboratory analyst must make this

choice. The analyst must balance analytical costs with uncertainty requirements and other factors.

Nevertheless, FTIR is probably a technically better method to analyze multiple-component mixtures

because interference effects are less likely to occur, provided that (1) the FTIR has sufficient spectral

resolution, (2) a “clean” peak is measured, (3) linearity problems are not encountered, and (4) accurate

gas standards are used for developing the reference spectra. Spectral resolution is the ability to distinguish

adjacent wavelengths. High-resolution spectra enable fine details within a spectrum to be observed, while

low resolution shows only gross features of a spectrum. The choice of spectral region to conduct the

measurement is important. If a sample contains a mixture of gases (some of which may not be the target

gas of interest), the potential exists for spectral bands to overlap. The overlapping bands can cause the

target gas to be overestimated. Analysis of a gas sample carried out using multivariate least squares

allows constituents in the gas sample that have overlapping spectral bands to be quantified with minimum

interference, as long as the measurements are conducted at a high spectral resolution and reference spectra

are generated using accurate standards. Non-linear responses can be corrected within the FTIR software

to provide accurate results.

The high-level CO2 FTIR results showed some significant deviations from the vendor tag value. For

example, the results of two high-level candidate gases with identical CO2 tag values (18.30 percent CO2)

were significantly different; one gas cylinder was found to be within 0.1 percent CO2 of the tag value,

while the other cylinder result differed from the tag value by approximately 1 percent CO2. To confirm

the results, the spectra of these two gases were directly compared. The CO2 spectra differed in absorbance

by 5 percent, confirming the results. This finding highlights the relatively high degree of differences for

these particular standards. Because the high-level CO2 reference spectra were not generated using a NIST

standard, however, EPA determined that the high-level CO2 FTIR data would not be used in the data

comparisons.

FTIR analysis of the gas standards also revealed an impurity issue that NIST is investigating. A visual

scan of the spectra indicated small amounts of impurities in the SO2 and CO2 reference standards. For

example, a spectrum of SRM 1694a containing 97.6 ppm SO2 in a nitrogen balance revealed the presence

of two impurities: 3.1 ppm NO and 100 ppb carbonyl sulfide. These impurities have no impact on the

FTIR analysis, but could be of concern when other methodologies are used. Some of the candidate

standards also included impurities. No effort was made to identify or quantify impurities in all of the 

SRM, NTRM and candidate standards. Visual inspection of the sample spectra, however, indicated that

some of the candidate standards contained small amounts of carbon monoxide (CO). The small amounts

of CO or any other impurity do not affect the FTIR analysis because they do not have absorption bands

near any of the analytes of interest. If an impurity has bands that overlap, measures can be taken to

account for the potential interference. No such measures were required in these analyses.

Accuracy assessments such as the one performed in this project provide a “snapshot” of the process

being evaluated. The results of the assessment presented here should therefore not be regarded as a final

statement on the accuracy of EPA Traceability Protocol gases, nor should the individual results be taken

as definitive critiques of the analytical capabilities of the individual manufacturers. Instead, the results

should be viewed as an indicator of the current status of the collective accuracy of the Protocol gases.
November 22, 2004 12

Table 6. NO Component Analysis Summary

Gas Vendor

Gas

Conc.

Range

Vendor-Supplied Information NO Analysis by UVa

 NO Analysis by FTIR

Tag

Value

(ppm NO)

Reanalyzed

Value

(ppm)

Change

in Value

(%)

NO

(ppm)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

NO

(ppm)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

Air Liquide Low 54.0 54.9 - 1.6 53.83 0.3

Mid 401 395.9 1.3 392.5 2.2

High 911 b

– 905 0.7

Airgas

Southwest

Specialty

Gases

Low 48.90 49.89c 2.0 53.4 - 8.4 - 6.5 49.93 - 2.1 - 0.1

Mid 406.0 405.2 - 0.2 411.7 - 1.4 - 1.6 406.3 - 0.1 - 0.3

High 900.0 909.8c 1.1 b

– – 925 - 2.7 - 1.6

Airgas NCN

Specialty

Gases

Low 51.4 52.21 1.6 53.2 - 3.4 - 1.9 51.50 - 0.2 1.4

Mid 388 384.6 - 0.9 387.2 0.2 - 0.7 382.4 1.5 0.6

High 845 860.9c 1.9 b

– – 870 - 2.9 - 1.0

Airgas South

Specialty

Gases

Low 50.05 51.69c 3.3 52.7 - 5.1 - 2.0 51.80 - 3.4 - 0.2

Mid 397.5 401 0.9 405.7 - 2.0 - 1.2 400.3 - 0.7 0.2

High 900.0 900.8 0.1 b – – 912 - 1.3 - 1.2

BOC Gases Low 49.8 51.5 - 3.3 50.50 - 1.4

Mid 407.8 406.0 d - 0.4 399.5 2.1 1.6 397.4 2.6 2.2

High 900 896 d - 0.4 b – – 880 2.3 1.8

AGA

(Linde Gas

Group)

Low 50.4 51.0 - 1.1 50.50 - 0.2

Mid 396 390.2 1.5 388.3 2.0

High 904 b

– 903 0.1

Matheson

Tri- Gas

Low 48.9 50.4e 3.1 51.5 - 5.0 - 2.1 50.57 - 3.3 - 0.3

Mid 410 405.1e - 1.2 401.6 2.1 0.9 397.7 3.1 1.9

High 904 b

– 907 - 0.3

Messer MG

Industries

Low 50.0 50.4 - 0.9 50.00 0.0

Mid 398 396.9 0.3 391.3 1.7

High 888 b – 887 0.1

Messer MG

Industries

(Spec Air

Gases)

Low 50.0 50.8 - 1.5 50.47 - 0.9

Mid 403 399.3 0.9 396.0 1.8

High 894 b – 904 - 1.1

National

Specialty

Gases

Low 46.2 47.3f 2.4 48.1 - 4.0 - 1.8 48.27 - 4.3 - 2.0

Mid 398 401.3 - 0.8 397.3 0.2

High 930 930 0.0 b

– – 948 - 1.9 - 1.9

Praxair Low 51.2 51.9 - 1.3 51.50 - 0.6

Mid 406 405.1 0.2 400.6 1.3

High 914 b

– 933 - 2.0

Scott Specialty

Gases

Low 50.0 51.0 - 1.9 50.30 - 0.6

Mid 402 401.7 0.1 397.2 1.2

High 911 b – 918 - 0.8

Scott- Marrin,

Inc.

Low 50.8 51.7 - 1.8 51.77 - 1.9

Mid 397 399.9 - 0.7 395.5 0.4

High 886 b

– 899 - 1.4
Table 6. NO Component Analysis Summary

Gas Vendor

Gas

Conc.

Range

Vendor-Supplied Information NO Analysis by UVa

 NO Analysis by FTIR

Tag

Value

(ppm NO)

Reanalyzed

Value

(ppm)

Change

in Value

(%)

NO

(ppm)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

NO

(ppm)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

November 22, 2004 13

Spectra Gases,

Inc.

Low 50.1 51.1 - 2.0 50.80 - 1.4

Mid 405 404.2 0.2 400.8 1.0

High 923 b

– 934 - 1.2

a AMETEK Model 922 UV measurements of NO were adjusted for SO2 interference.

b

 The high-level NO evaluations were based solely on the FTIR results because the AMETEK UV NOx analyzer setup

performed by the manufacturer was not optimum for the 1000-ppm range.

c

 Gas cylinders were returned to Airgas for NO reanalyses. Vendor reported new NO values on April 26, 2004, which differed

by less than ± 2 percent from the corresponding EPA-determined values. In all but one case, the reanalyzed value was within

± 2 percent of the original tag value. No corrective action was taken by the vendor.

d

 Mid- and high-level gas cylinders were returned to BOC Gases for NO reanalyses. Vendor reported new values on June 9,

2004, which differed by less than ± 2 percent from the corresponding EPA-determined UV or FTIR values. The two

reanalyzed NO values also differed by less than ± 2 percent of original tag value. No corrective action was taken.

e

 Gas cylinders were returned to Matheson for NO and CO2 reanalyses. Vendor reported new values on May 10, 2004, which

differed by less than ± 2 percent from the corresponding EPA-determined values. Two of the three reanalyzed values differed

by more than ± 2 percent of original tag value. The concentrations for NO were corrected by shifting to a wave number within

a spectral region where CO2 interference is minimized. Matheson found an operator calculation error for the CO2

concentration in this sample from early 2003, and implemented data acquisition and calculation software for their FTIRs in

early 2004 to preclude the potential for operator errors.

f

 Gas cylinders were returned to National Specialty Gases for NO, SO2, and CO2 reanalyses. Vendor reported new values on

May 10, 2004, which differed by less than ± 2 percent from the corresponding EPA-determined values. Two of the three

reanalyzed values differed by more than ± 2 percent of original tag value. The FTIR problem was corrected during the course

of the regular calibration cycle and by using a more experienced analyst.

NOTE: When using data in the tables for procuring EPA Traceability Protocol gases, readers should heed the following points.

First, the information in the footnotes must not be ignored. Second, if the difference between EPA’s value and the gas vendor’s

value is ± 2 percent or less, the values do not statistically differ because of the uncertainties in the total measurement system.

Thus, a difference of 2.0 percent would be interpreted as being equal to one of, for example, 0.57 percent. Finally, EPA presents

this information without assigning a rating to the gas vendors, such as which vendor is approved, or which is not approved.

Table 7. SO2 Component Analysis Summary

Gas Vendor

Gas

Conc.

Range

Vendor-Supplied Information SO2 Analysis by UV SO2 Analysis by FTIR

Tag

Value

(ppm SO2)

Reanalyzed

Value

(ppm)

Change

in Value

(%)

SO2

(ppm)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

SO2

(ppm)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

Air Liquide Low 47.5 48.36 - 1.8 47.93 - 0.9

Mid 499 497.17 0.4 498.5 0.1

High 981 987.26 - 0.6 1004.5 - 2.3

Airgas

Southwest

Specialty

Gases

Low 47.73 47.62 - 0.2 47.01 1.5 1.3 47.52 0.4 0.2

Mid 496.8 500.9 0.8 492.10 1.0 1.8 501.3 - 0.9 - 0.1

High 994.6 1003 0.8 994.16 0.0 0.9 1008.2 - 1.3 - 0.5

Airgas NCN

Specialty

Gases

Low 50.4 50.05 - 0.7 49.92 1.0 0.3 49.79 1.2 0.5

Mid 500 504.3 0.9 499.89 0.0 0.9 504.2 - 0.8 0.0

High 1000 1002 0.2 1000.28 0.0 0.2 1006.8 - 0.7 - 0.5

Airgas South

Specialty

Gases

Low 50.23 51.03 1.6 50.25 0.0 1.6 50.58 - 0.7 0.9

Mid 502.8 509.2 1.3 505.89 - 0.6 0.7 507.9 - 1.0 0.3

High 998.8 1012 1.3 1003.99 - 0.5 0.8 1016.1 - 1.7 - 0.4
Table 7. SO2 Component Analysis Summary

Gas Vendor

Gas

Conc.

Range

Vendor-Supplied Information SO2 Analysis by UV SO2 Analysis by FTIR

Tag

Value

(ppm SO2)

Reanalyzed

Value

(ppm)

Change

in Value

(%)

SO2

(ppm)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

SO2

(ppm)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

November 22, 2004 14

BOC Gases Low 50.9 50.52 0.8 50.83 0.1

Mid 500.4 499.80 0.1 499.8 0.1

High 1000 1001.47 - 0.1 1015.6 - 1.5

AGA

(Linde Gas

Group)

Low 48.7 48.67 0.1 49.54 - 1.7

Mid 466 461.75 0.9 464.2 0.4

High 956 955.83 0.0 967.3 - 1.2

Matheson

Tri- Gas

Low 49.5 48.33 2.4 48.95 1.1

Mid 504 502.79 0.2 503.6 0.1

High 988 994.28 - 0.6 1006.5 - 1.8

Messer MG

Industries

Low 50.1 48.89 2.5 49.26 1.7

Mid 501 506.49 - 1.1 508.5 - 1.5

High 1004 1018.01 - 1.4 1029.3 - 2.5

Messer MG

Industries

(Spec Air

Gases)

Low 49.3 48.16 2.4 49.12 0.4

Mid 496 502.94 - 1.4 504.0 - 1.6

High 1004 1018.22 - 1.4 1029.8 - 2.5

National

Specialty

Gases

Low 51.8 51.5a - 0.6 50.49 2.6 2.0 50.64 2.3 1.7

Mid 500 499.12 0.2 502.2 - 0.4

High 991 992 0.1 995.74 - 0.5 - 0.4 1011.0 - 2.0 - 1.9

Praxair Low 50.0 49.59 0.8 50.36 - 0.7

Mid 509 506.59 0.5 511.6 - 0.5

High 999 1000.59 - 0.2 1008.7 - 1.0

Scott Specialty

Gases

Low 50.4 49.10 2.7 50.38 0.0

Mid 503 497.63 1.1 503.0 0.0

High 1011 1000.65 1.0 1021.3 - 1.0

Scott- Marrin,

Inc.

Low 50.9 51.07 - 0.3 51.17 - 0.5

Mid 504 502.94 0.2 507.9 - 0.8

High 997 992.93 0.4 995.9 0.1

Spectra Gases,

Inc.

Low 50.2 49.19 2.1 49.82 0.8

Mid 495 493.05 0.4 493.1 0.4

High 988 987.60 0.0 998.5 - 1.1

a Gas cylinders were returned to National Specialty Gases for NO, SO2, and CO2 reanalyses. Vendor reported new values on May

10, 2004, which differed by less than ± 2 percent from the corresponding EPA-determined values. Two of the three reanalyzed

values differed by more than ± 2 percent of original tag value. FTIR problem was corrected during the course of the regular

calibration cycle and using a more experienced analyst.

NOTE: When using data in the tables for procuring EPA Traceability Protocol gases, readers should heed the following points.

First, the information in the footnotes must not be ignored. Second, if the difference between EPA’s value and the gas vendor’s

value is ± 2 percent or less, the values do not statistically differ because of the uncertainties in the total measurement system.

Thus, a difference of 2.0 percent would be interpreted as being equal to one of, for example, 0.57 percent. Finally, EPA presents

this information without assigning a rating to the gas vendors, such as which vendor is approved, or which is not approved.
November 22, 2004 15

Table 8. CO2 Component Analysis Summary

Gas Vendor

Gas

Conc.

Range

Vendor-Supplied Information CO2 Analysis by NDIR CO2 Analysis by FTIR

Tag

Value

(% CO2)

Reanalyzed

Value

(% CO2)

Change

in Value

(%)

CO2

(%)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

CO2

(%)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

Air Liquide Low 4.97 5.02 - 1.0 4.991 - 0.4

Mid 12.1 12.09 0.1 11.98 1.0

High 17.7 17.9a 1.1 18.15 - 2.5 - 1.4 b

– –

Airgas

Southwest

Specialty Gases

Low 5.011 5.045 0.7 4.97 0.8 1.5 4.984 0.5 1.2

Mid 12.0 11.95 - 0.4 12.07 - 0.6 - 1.0 12.06 - 0.5 - 0.9

High 17.99 17.97 - 0.1 18.09 - 0.6 - 0.7 b

– –

Airgas NCN

Specialty Gases

Low 5.01 5.064 1.1 5.00 0.2 1.3 4.970 0.8 1.9

Mid 12.0 11.94 - 0.5 12.07 - 0.6 - 1.1 12.04 - 0.3 - 0.8

High 18.0 18.06 0.3 18.15 - 0.8 - 0.5 b– –

Airgas South

Specialty Gases

Low 5.041 5.057 0.3 5.01 0.7 1.0 4.998 0.9 1.2

Mid 12.0 11.88 - 1.0 12.05 - 0.4 - 1.4 12.17 - 1.4 - 2.4

High 18.07 18.15 0.4 18.18 - 0.6 - 0.2 b

– –

BOC Gases Low 5.0 4.98 0.5 4.973 0.5

Mid 11.98 12.05 - 0.6 11.94 0.3

High 18.02 18.14 - 0.7 b

–

AGA

(Linde Gas

Group)

Low 5.2 5.22 - 0.5 5.146 1.0

Mid 12.5 12.68 - 1.4 12.45 0.4

High 18.3 18.53 - 1.2 b

–

Matheson

Tri- Gas

Low 5.23 4.94c - 5.5 4.99 4.8 - 1.0 4.979 5.0 - 0.8

Mid 12.2 12.06 1.2 11.93 2.3

High 17.9 18.07 - 0.9 b –

Messer MG

Industries

Low 5.05 5.08 - 0.5 5.023 0.5

Mid 12.1 12.22 - 1.0 12.18 - 0.7

High 18.2 18.27 - 0.4 b

–

Messer MG

Industries

(Spec Air

Gases)

Low 5.07 5.09 - 0.5 5.053 0.3

Mid 12.1 12.22 - 1.0 12.18 - 0.7

High 18.3 18.31 - 0.1 b

–

National

Specialty Gases

Low 4.9 4.9 0.0 4.87 0.5 0.5 4.885 0.3 0.3

Mid 12.0 11.97 0.3 12.09 - 0.7

High 17.8 18.23d 2.4 18.30 - 2.8 - 0.4 b

– –

Praxair Low 5.00 5.03 - 0.6 4.986 0.3

Mid 12.18 12.17 0.1 12.23 - 0.4

High 17.59 17.82e 1.3 17.85 - 1.5 - 0.2 b – –

Scott Specialty

Gases

Low 5.04 5.01 0.6 4.987 1.1

Mid 12.10 12.04 0.5 12.18 - 0.7

High 17.97 18.03 - 0.3 b

–

Scott-Marrin,

Inc.

Low 5.11 5.09 0.4 5.046 1.3

Mid 12.02 12.11 - 0.7 12.07 - 0.4

High 17.92 18.13 - 1.2 b –
Table 8. CO2 Component Analysis Summary

Gas Vendor

Gas

Conc.

Range

Vendor-Supplied Information CO2 Analysis by NDIR CO2 Analysis by FTIR

Tag

Value

(% CO2)

Reanalyzed

Value

(% CO2)

Change

in Value

(%)

CO2

(%)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

CO2

(%)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

November 22, 2004 16

Spectra Gases,

Inc.

Low 5.02 5.01 0.1 5.003 0.3

Mid 12.03 12.10 - 0.5 12.24 - 1.7

High 18.07 18.08 0.0 b

–

a High-range gas cylinder was returned to Air Liquide for CO2 reanalysis. Vendor reported a new CO2 value of 17.9 percent on May

6, 2004, which differed by less than ± 2 percent from the EPA-determined value. Reanalyzed value was also within ± 2 percent

of original tag value. No corrective action was taken by the vendor.

b The high-level CO2 evaluations were based solely on the NDIR results because the FTIR data obtained at this concentration

level were not supported by an SRM; sufficient high-level CO2 SRM or NTRM was not available to provide reference spectra for

the FTIR.

c Gas cylinders were returned to Matheson for NO and CO2 reanalyses. Vendor reported new values on May 10, 2004, which

differed by less than ± 2 percent from the corresponding EPA-determined values. Two of the three reanalyzed values differed by

more than ± 2 percent of original tag value. The concentrations for NO were corrected by shifting to a wave number within a

spectral region where CO2 interference is minimized. Matheson found an operator calculation error for the CO2 concentration in

this sample from early 2003, and implemented data acquisition and calculation software for their FTIRs in early 2004 to preclude

the potential for operator errors.

d Gas cylinders were returned to National Specialty Gases for NO, SO2, and CO2 reanalyses. Vendor reported new values on May

10, 2004, which differed by less than ± 2 percent from the corresponding EPA-determined values. Two of the three reanalyzed

values differed by more than ± 2 percent of original tag value. The FTIR problem was corrected during the course of the regular

calibration cycle and by using a more experienced analyst.

e High-range gas cylinder was returned to Praxair for CO2 reanalysis based on an initial EPA finding of 18.07 percent CO2. Vendor

reported a new CO2 value of 17.82 percent on May 27, 2004. Praxair had an independent, third-party laboratory (Scott-Marin,

Inc.) analyze the cylinder, resulting in 17.77 percent CO2. Praxair also sent the cylinder to NIST for analysis, which resulted in

17.85 percent CO2. All of the reanalyzed values differed by less than 2.0 percent from the EPA-determined value. The original

tag value was within 2.0 percent of each of the reanalyzed values. The original tag value and the vendor-reanalyzed value were

within 2.0 percent of the NIST-generated "true" value. Therefore, no corrective action was required.

NOTE: When using data in the tables for procuring EPA Traceability Protocol gases, readers should heed the following points.

First, the information in the footnotes must not be ignored. Second, if the difference between EPA’s value and the gas vendor’s

value is ± 2 percent or less, the values do not statistically differ because of the uncertainties in the total measurement system.

Thus, a difference of 2.0 percent would be interpreted as being equal to one of, for example, 0.57 percent. Finally, EPA presents

this information without assigning a rating to the gas vendors, such as which vendor is approved, or which is not approved.

6.0 CONSIDERATIONS FOR FUTURE PROTOCOL GAS AUDITS

The following are elements of the audit that warrant consideration before the next audit of blended

gases is performed.

• When analyzing multi-component gas blends, the analyst must conduct an interference test to

verify instrument vendor claims that the analyzer is free of any interferences or that interference

correction is properly applied. The instrument calibration should be well characterized using both

single-component and multi-component reference standards. Example interference issues are CO2

quenching in chemiluminescence-based techniques, SO2 interference in the UV measurement of

NO, and impurities in the gas standards.

• One instrument vendor stated that cross-interference of 1 percent of full scale is their standard

specification. The ± 2 percent acceptance criterion (relative to the analyzed value, not full scale)

used for these audits accommodates the ± 1 percent uncertainty in the concentrations of NIST

SRMs and the ± 1 percent uncertainty in the balance of the measurement system used to produce

Protocol gases. This acceptance criterion becomes more stringent with possible interference effects
November 22, 2004 17

in multi-component gas analyses, even though the interference error may be within the instrument

performance specifications.

• EPA’s Traceability Protocol should include detailed procedures that are specific to FTIR-based

cylinder gas analysis. Some potential issues arose during this study when making quantitative

measurements using FTIR, and NIST occasionally had difficulty trying to correlate gas vendor

FTIR results for NTRM analyses with the NIST non-FTIR analyses. Standard operating procedures

(SOP) for FTIR analysis of cylinder gases may help eliminate potential problems and ensure that

all FTIR measurement data are generated using consistent analytical routines and reported in the

same manner.

An approach to the development of a draft FTIR SOP could include the following steps: (a)

review existing public guidance documents from, for example, EPA, ASTM, NIOSH, OEDC, and

TUV; (b) survey of gas manufacturers' approaches to QA/QC in such applications, including

reviews of any in-house documents the manufacturers are willing to submit; (c) development of a

list of key SOP elements, with the goal of reaching the broadest possible consensus among

manufacturers and analysts; and (d) preparation of a draft SOP containing these elements.

Various approaches can be considered in determining selection criteria for audit targets. Given that the

gas vendors use these audit results as a marketing tool, however, the next audit should include all

specialty gas companies that produce EPA Protocol gas. Currently, 10 specialty gas companies produce

EPA Protocol gas. Considering how transfers of gas business entities between companies have occurred

over the past few years, the survey should be repeated to identify any changes in this list of gas producers.
APPENDIX A. GAS MEASUREMENT DATA AND COMPARISONS
Table A-1. NO Component Analyses

Gas Vendor

Gas

Conc.

Range

Vendor-Supplied Information NO Analysis by UVa 

Tag

Value

(ppm NO)

Uncert.

(±)

Reanalyzed

Value

(ppm)

Change

in Value

(%)

NO

(ppm)

Uncert.

(± ppm)

95% CI

(ppm)

Relative

CI

(%)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

NO

(ppm)

95 % 

(ppm

Air Liquide Low 54.0 0.8 ppm 54.9 1.3 0.2 0.34 - 1.6 53.83 0

Mid 401 5 ppm 395.9 3.0 2.3 0.59 1.3 392.5 

High 911 10 ppm

b

– – – – 905 

AirgasSouthwestSpecialty Gases

Low 48.90 1 % 49.89c 2.0 53.4 1.9 0.3 0.51 - 8.4 - 6.5 49.93 0

Mid 406.0 1 % 405.2 - 0.2 411.7 3.1 0.4 0.11 - 1.4 - 1.6 406.3 

High 900.0 1 % 909.8c 1.1 b – – – – – 925 

Airgas NCNSpecialty Gases

Low 51.4 1 % 52.21 1.6 53.2 1.3 0.4 0.73 - 3.4 - 1.9 51.50 0

Mid 388 1 % 384.6 - 0.9 387.2 3.0 0.7 0.18 0.2 - 0.7 382.4 

High 845 1 % 860.9c 1.9 b – – – – – 870 

Airgas SouthSpecialty Gases

Low 50.05 1 % 51.69c 3.3 52.7 1.3 0.2 0.45 - 5.1 - 2.0 51.80 0

Mid 397.5 1 % 401 0.9 405.7 3.0 1.2 0.30 - 2.0 - 1.2 400.3 

High 900.0 1 % 900.8 0.1

b

– – – – – 912 

BOC Gases Low 49.8 1 % 51.5 1.3 0.4 0.83 - 3.3 50.50 0

Mid 407.8 1 % 406.0d - 0.4 399.5 3.0 0.6 0.16 2.1 1.6 397.4 

High 900 1 % 896d - 0.4 b – – – – – 880 

AGA(Linde GasGroup)

Low 50.4 0.5 ppm 51.0 1.3 0.1 0.13 - 1.1 50.50 0

Mid 396 4 ppm 390.2 2.4 0.2 0.06 1.5 388.3 

High 904 9 ppm

b

– – – – 903 

MathesonTri- Gas

Low 48.9 0.4 ppm 50.4e 3.1 51.5 1.3 0.1 0.15 - 5.0 - 2.1 50.57 0

Mid 410 1 ppm 405.1e - 1.2 401.6 3.0 1.6 0.41 2.1 0.9 397.7 

High 904 9 ppm

b

– – – – 907 

Messer MGIndustries

Low 50.0 0.128 ppm 50.4 1.3 0.1 0.20 - 0.9 50.00 0

Mid 398 1.28 ppm 396.9 3.0 0.2 0.06 0.3 391.3 

High 888 2.99 ppm

b

– – – – 887 

Messer MGIndustries(Spec AirGases)

Low 50.0 0.131 ppm 50.8 1.3 0.3 0.58 - 1.5 50.47 0

Mid 403 1.28 ppm 399.3 2.5 0.9 0.22 0.9 396.0 

High 894 2.99 ppm

b

– – – – 904 
Table A-1. NO Component Analyses

Gas Vendor

Gas

Conc.

Range

Vendor-Supplied Information NO Analysis by UVa 

Tag

Value

(ppm NO)

Uncert.

(±)

Reanalyzed

Value

(ppm)

Change

in Value

(%)

NO

(ppm)

Uncert.

(± ppm)

95% CI

(ppm)

Relative

CI

(%)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

NO

(ppm)

95 % 

(ppm

NationalSpecialty Gases

Low 46.2 1 % 47.3f 2.4 48.1 1.3 0.4 0.92 - 4.0 - 1.8 48.27 0

Mid 398 1 % 401.3 2.5 0.6 0.14 - 0.8 397.3 

High 930 1 % 930 0.0

b

– – – – – 948 

Praxair Low 51.2 1 % 51.9 1.3 0.3 0.59 - 1.3 51.50 0

Mid 406 1 % 405.1 2.5 0.4 0.11 0.2 400.6 1

High 914 1 %

b

– – – – 933 

Scott SpecialtyGases

Low 50.0 1 % 51.0 1.3 0.3 0.63 - 1.9 50.30 0

Mid 402 1 % 401.7 2.5 2.2 0.55 0.1 397.2 

High 911 1 %

b

– – – – 918 

Scott- Marrin,Inc.

Low 50.8 0.3 ppm 51.7 1.3 0.1 0.14 - 1.8 51.77 0

Mid 397 2 ppm 399.9 2.5 0.9 0.22 - 0.7 395.5 

High 886 5 ppm

b

– – – – 899 

Spectra Gases,Inc.

Low 50.1 1 % 51.1 1.3 0.3 0.65 - 2.0 50.80 0

Mid 405 1 % 404.2 2.5 0.8 0.21 0.2 400.8 

High 923 1 %

b

– – – – 934 

a AMETEK Model 922 UV measurements of NO were adjusted for SO2 interference.b The high-level NO evaluations were based solely on the FTIR results because the AMETEK UV NOx analyzer setup performed by the manufacturer was not optc Gas cylinders were returned to Airgas for NO reanalyses. Vendor reported new NO values on April 26, 2004, which differed by less than 2 percent from the corr

all but one case, the reanalyzed value was within ± 2 percent of original tag value. No corrective action taken by the vendor.

d Mid- and high-level gas cylinders were returned to BOC Gases for NO reanalyses. Vendor reported new values on June 9, 2004, which differed by less than 2 p

determined UV or FTIR values. The two reanalyzed NO values also differed by less than 2 percent of original tag value. No corrective action was taken.

e Gas cylinders were returned to Matheson for NO and CO2 reanalyses. Vendor reported new values on May 10, 2004, which differed by less than 2 percent from 

values. Two of the three reanalyzed values differed by more than 2 percent of original tag value. The NO concentrations were corrected by shifting to a wave nu

CO2 interference is minimized. Matheson found an operator calculation error for the CO2 concentration in this sample from early 2003, and implemented data ac

their FTIRs in early 2004 to preclude the potential for operator errors.

g Gas cylinders were returned to National Specialty Gases for NO, SO2, and CO2 reanalyses. Vendor reported new values on May 10, 2004, which differed by les

EPA-determined values. Two of the three reanalyzed values differed by more than 2 percent of original tag value. FTIR problem was corrected during the course 

using a more experienced analyst.

NOTE: When using data in the tables for procuring EPA Traceability Protocol gases, readers should heed the following points. First, the information in the footnotes 

difference between EPA’s value and the gas vendor’s value is ± 2 percent or less, the values do not statistically differ because of the uncertainties in the total meas

2.0 percent would be interpreted as being equal to one of, for example, 0.57 percent. Finally, EPA presents this information without assigning a rating to the gas ve

approved, or which is not approved.
Table A-2. SO2 Component Analyses

Gas Vendor

Gas

Conc.

Range

Vendor-Supplied Information SO2 Analysis by UV 

Tag

Value

(ppm SO2)

Uncert.

(±)

Reanalyzed

Value

(ppm)

Change

in Value

(%)

SO2

(ppm)

Uncert.

(± ppm)

95% CI

(ppm)

Relative

CI

(%)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

SO2

(ppm)

95 

(p

Air Liquide Low 47.5 0.8 ppm 48.36 2.88 0.37 0.76 - 1.8 47.93 

Mid 499 4 ppm 497.17 3.13 0.76 0.15 0.4 498.5 

High 981 9 ppm 987.26 3.29 1.66 0.17 - 0.6 1004.5 

AirgasSouthwestSpecialty Gases

Low 47.73 1 % 47.62 - 0.2 47.01 2.88 0.33 0.70 1.5 1.3 47.52 

Mid 496.8 1 % 500.9 0.8 492.10 3.13 3.09 0.63 1.0 1.8 501.3 

High 994.6 1 % 1003 0.8 994.16 3.96 5.08 0.51 0.0 0.9 1008.2 

Airgas NCNSpecialty Gases

Low 50.4 1 % 50.05 - 0.7 49.92 2.93 0.01 0.02 1.0 0.3 49.79 

Mid 500 1 % 504.3 0.9 499.89 3.17 0.35 0.07 0.0 0.9 504.2 

High 1000 1 % 1002 0.2 1000.28 3.96 2.43 0.24 0.0 0.2 1006.8 

Airgas SouthSpecialty Gases

Low 50.23 1 % 51.03 1.6 50.25 2.88 0.03 0.05 0.0 1.6 50.58 

Mid 502.8 1 % 509.2 1.3 505.89 3.14 0.39 0.08 - 0.6 0.7 507.9 

High 998.8 1 % 1012 1.3 1003.99 4.01 1.61 0.16 - 0.5 0.8 1016.1 

BOC Gases Low 50.9 1 % 50.52 2.70 0.15 0.29 0.8 50.83 

Mid 500.4 1 % 499.80 3.13 0.71 0.14 0.1 499.8 

High 1000 1 % 1001.47 3.96 0.31 0.03 - 0.1 1015.6 

AGA(Linde GasGroup)

Low 48.7 0.5 ppm 48.67 2.70 0.13 0.28 0.1 49.54 

Mid 466 5 ppm 461.75 3.04 5.57 1.21 0.9 464.2 

High 956 10 ppm 955.83 3.87 2.25 0.24 0.0 967.3 

MathesonTri- Gas

Low 49.5 0.4 ppm 48.33 2.76 0.22 0.45 2.4 48.95 

Mid 504 5 ppm 502.79 3.04 1.70 0.34 0.2 503.6 

High 988 9 ppm 994.28 5.30 7.08 0.71 - 0.6 1006.5 

Messer MGIndustries

Low 50.1 0.507 ppm 48.89 2.70 0.23 0.46 2.5 49.26 

Mid 501 1.82 ppm 506.49 3.09 0.43 0.09 - 1.1 508.5 

High 1004 3.1 ppm 1018.01 5.36 2.19 0.21 - 1.4 1029.3 

Messer MGIndustries(Spec AirGases)

Low 49.3 0.506 ppm 48.16 2.70 0.66 1.38 2.4 49.12 

Mid 496 1.82 ppm 502.94 3.04 0.66 0.13 - 1.4 504.0 

High 1004 3.1 ppm 1018.22 5.40 1.92 0.19 - 1.4 1029.8 
Table A-2. SO2 Component Analyses

Gas Vendor

Gas

Conc.

Range

Vendor-Supplied Information SO2 Analysis by UV 

Tag

Value

(ppm SO2)

Uncert.

(±)

Reanalyzed

Value

(ppm)

Change

in Value

(%)

SO2

(ppm)

Uncert.

(± ppm)

95% CI

(ppm)

Relative

CI

(%)

Orig Tag

Value

Deviation

(% diff)

Reanalyzed

Value

Deviation

(% diff)

SO2

(ppm)

95 

(p

NationalSpecialty Gases

Low 51.8 1 % 51.5a - 0.6 50.49 2.75 0.22 0.44 2.6 2.0 50.64 

Mid 500 1 % 499.12 3.04 3.39 0.68 0.2 502.2 

High 991 1 % 992 0.1 995.74 5.30 2.35 0.24 - 0.5 - 0.4 1011.0 

Praxair Low 50.0 1 % 49.59 2.75 0.19 0.38 0.8 50.36 

Mid 509 1 % 506.59 2.83 3.11 0.61 0.5 511.6 

High 999 1 % 1000.59 5.31 6.58 0.66 - 0.2 1008.7 

Scott SpecialtyGases

Low 50.4 1 % 49.10 2.81 0.18 0.38 2.7 50.38 

Mid 503 1 % 497.63 2.83 2.63 0.53 1.1 503.0 

High 1011 1 % 1000.65 3.83 4.28 0.43 1.0 1021.3 

Scott-Marrin,Inc.

Low 50.9 0.6 ppm 51.07 2.75 0.12 0.23 - 0.3 51.17 

Mid 504 5 ppm 502.94 2.87 0.88 0.17 0.2 507.9 

High 997 10 ppm 992.93 3.81 3.28 0.33 0.4 995.9 

Spectra Gases,Inc.

Low 50.2 1 % 49.19 2.75 0.18 0.37 2.1 49.82 

Mid 495 1 % 493.05 2.83 0.85 0.17 0.4 493.1 

High 988 1 % 987.60 3.85 1.15 0.12 0.0 998.5 

a Gas cylinders were returned to National Specialty Gases for NO, SO2, and CO2 reanalyses. Vendor reported new values on May 10, 2004, which differed by les

EPA-determined values. Two of the three reanalyzed values differed by more than 2 percent of original tag value. An FTIR problem was corrected during the co

by using a more experienced analyst.

NOTE: When using data in the tables for procuring EPA Traceability Protocol gases, readers should heed the following points. First, the information in the footnotes 

difference between EPA’s value and the gas vendor’s value is ± 2 percent or less, the values do not statistically differ because of the uncertainties in the total meas

2.0 percent would be interpreted as being equal to one of, for example, 0.57 percent. Finally, EPA presents this information without assigning a rating to the gas ve

approved, or which is not approved.
Table A-3. CO2 Component Analyses

Gas Vendor

Gas

Conc.

Range

Vendor-Supplied Information CO2 Analysis by NDIR 

Tag

Value

(ppm CO2)

Uncert.

(±)

Reanalyze

d Value

(% CO2)

Change

in Value

(%)

CO2

(%)

Uncert.

(± % CO2)

95 % CI

(% CO2)

Relative

CI

(%)

Orig Tag

Value

Deviation

(% diff)

Reanalyze

d Value

Deviation

(% diff)

CO2

(%)

95 % 

(% C

Air Liquide Low 4.97 0.06 % CO2 5.02 0.07 0.01 0.12 - 1.0 4.991 0

Mid 12.1 0.1 % CO2 12.09 0.11 0.02 0.18 0.1 11.98 

High 17.7 0.2 % CO2 17.9a 1.1 18.15 0.17 0.01 0.08 - 2.5 - 1.4 b 

AirgasSouthwestSpecialty Gases

Low 5.011 1 % 5.045 0.7 4.97 0.07 0.01 0.26 0.8 1.5 4.984 0

Mid 12.0 1 % 11.95 - 0.4 12.07 0.11 0.01 0.11 - 0.6 - 1.0 12.06 

High 17.99 1 % 17.97 - 0.1 18.09 0.17 0.01 0.04 - 0.6 - 0.7

b

Airgas NCNSpecialty Gases

Low 5.01 1 % 5.064 1.1 5.00 0.07 0.01 0.10 0.2 1.3 4.970 0

Mid 12.0 1 % 11.94 - 0.5 12.07 0.11 0.01 0.09 - 0.6 - 1.1 12.04 

High 18.0 1 % 18.06 0.3 18.15 0.17 0.00 0.01 - 0.8 - 0.5

b

Airgas SouthSpecialty Gases

Low 5.041 1 % 5.057 0.3 5.01 0.07 0.01 0.22 0.7 1.0 4.998 0

Mid 12.0 1 % 11.88 - 1.0 12.05 0.11 0.01 0.09 - 0.4 - 1.4 12.17 

High 18.07 1 % 18.15 0.4 18.18 0.17 0.02 0.11 - 0.6 - 0.2

b

BOC Gases Low 5.0 1 % 4.98 0.07 0.01 0.22 0.5 4.973 0

Mid 11.98 1 % 12.05 0.11 0.01 0.06 - 0.6 11.94 

High 18.02 1 % 18.14 0.17 0.01 0.06 - 0.7

b

AGA(Linde GasGroup)

Low 5.2 0.5 % CO2 5.22 0.07 0.01 0.17 - 0.5 5.146 0

Mid 12.5 0.1 % CO2 12.68 0.12 0.01 0.04 - 1.4 12.45 

High 18.3 0.2 % CO2 18.53 0.17 0.02 0.08 - 1.2

b

MathesonTri-Gas

Low 5.23 0.05 % CO2 4.94c - 5.5 4.99 0.07 0.01 0.28 4.8 - 1.0 4.979 0

Mid 12.2 0.1 % CO2 12.06 0.11 0.01 0.11 1.2 11.93 

High 17.9 0.1 % CO2 18.07 0.17 0.00 0.02 - 0.9

b

Messer MGIndustries

Low 5.05 0.0444 % CO2 5.08 0.07 0.01 0.23 - 0.5 5.023 0

Mid 12.1 0.0501 % CO2 12.22 0.11 0.02 0.13 - 1.0 12.18 

High 18.2 0.0501 % CO2 18.27 0.17 0.00 0.02 - 0.4

b

Messer MGIndustries(Spec AirGases)

Low 5.07 0.04444 % CO2 5.09 0.07 0.01 0.12 - 0.5 5.053 0

Mid 12.1 0.0501 % CO2 12.22 0.11 0.01 0.10 - 1.0 12.18 

High 18.3 0.0501 % CO2 18.31 0.17 0.00 0.01 - 0.1

b

NationalSpecialty Gases

Low 4.9 1 % 4.9 0.0 4.87 0.06 0.01 0.11 0.6 0.6 4.885 0

Mid 12.0 1 % 11.97 0.11 0.01 0.08 0.3 12.09 

High 17.8 1 % 18.23d 2.4 18.30 0.17 0.01 0.04 - 2.8 - 0.4 b 
Table A-3. CO2 Component Analyses

Gas Vendor

Gas

Conc.

Range

Vendor-Supplied Information CO2 Analysis by NDIR 

Tag

Value

(ppm CO2)

Uncert.

(±)

Reanalyze

d Value

(% CO2)

Change

in Value

(%)

CO2

(%)

Uncert.

(± % CO2)

95 % CI

(% CO2)

Relative

CI

(%)

Orig Tag

Value

Deviation

(% diff)

Reanalyze

d Value

Deviation

(% diff)

CO2

(%)

95 % 

(% C

Praxair Low 5.00 1 % 5.03 0.06 0.00 0.05 - 0.6 4.986 0

Mid 12.18 1 % 12.17 0.11 0.02 0.16 0.1 12.23 

High 17.59 1 % 17.82e 1.3 17.85 0.13 0.01 0.06 - 1.5 - 0.2 b 

Scott SpecialtyGases

Low 5.04 1 % 5.01 0.06 0.00 0.03 0.6 4.987 0

Mid 12.10 1 % 12.04 0.11 0.01 0.07 0.5 12.18 

High 17.97 1 % 18.03 0.17 0.01 0.07 - 0.3

b

Scott-Marrin,Inc.

Low 5.11 0.05 % CO2 5.09 0.06 0.00 0.03 0.4 5.046 0

Mid 12.02 0.02 % CO2 12.11 0.11 0.01 0.07 - 0.7 12.07 

High 17.92 0.05 % CO2 18.13 0.17 0.02 0.12 - 1.2

b

Spectra Gases,Inc.

Low 5.02 1 % 5.01 0.06 0.01 0.13 0.1 5.003 0

Mid 12.03 1 % 12.10 0.11 0.01 0.07 - 0.5 12.24 

High 18.07 1 % 18.08 0.17 0.01 0.05 0.0

b

 a High-range gas cylinder was returned to Air Liquide for CO2 reanalysis. Vendor reported a new CO2 value of 17.9 percent on May 6, 2004, which differs by less 

determined value. Reanalyzed value is also within ± 2 percent of original tag value. No corrective action taken by the vendor.

b The high-level CO2 evaluations were based solely on the NDIR results because the FTIR data obtained at this concentration level were not supported by an S

NTRM was available to provide reference spectra for the FTIR.

c Gas cylinders were returned to Matheson for NO and CO2 reanalyses. Vendor reported new values on May 10, 2004, which differed by less than ± 2 percent fr

values. Two of the three reanalyzed values differed by more than ± 2 percent of original tag value. The NO concentrations were corrected by shifting to a wave CO2 interference is minimized. Matheson found an operator calculation error for the CO2 concentration in this sample from early 2003, and implemented data a

their FTIRs in early 2004 to preclude the potential for operator errors.

d Gas cylinders were returned to National Specialty Gases for NO, SO2, and CO2 reanalyses. Vendor reported new values on May 10, 2004, which differed by le

corresponding EPA-determined values. Two of the three reanalyzed values differed by more than ± 2 percent of original tag value. FTIR problem was correctecalibration cycle and using a more experienced analyst.

e High-range gas cylinder was returned to Praxair for CO2 reanalysis based on an initial EPA finding of 18.07 percent CO2. Vendor reported a new CO2 value of 

had an independent, third-party laboratory (Scott-Marin, Inc.) analyze the cylinder, resulting in 17.77 percent CO2. Praxair also sent the cylinder to NIST for an

of the reanalyzed values differed by less than 2.0 percent from the EPA-determined value. The original tag value was within 2.0 percent of each of the reanalythe vendor reanalyzed value were within 2.0 percent of the NIST-generated "true" value. Therefore, no corrective action was required.

NOTE: When using data in the tables for procuring EPA Traceability Protocol gases, readers should bear in mind the following points. First, the information in the fo

not be ignored. Second, if the difference between EPA’s value and the gas vendor’s value differs by ± 2 percent or less, then (because of the uncertainties in the tothere is no difference between the two values. Thus, a difference of 2.0 percent would be interpreted as being equal to one of, for example, 0.57 percent. Third, EPassigning a rating to the gas vendors, for example, who is the best, who is approved, or who is not approved.
Table A-4. MACTEC Analysis Data

Gas Vendor

Gas

Conc.

Range

NO Analysis by UV SO2 Analysis by UV CO2 Ana

Run 1(ppm)

Run 2(ppm)

Run 3(ppm)

Avg.

(ppm)

CorrAvg.

(ppm) sd

95 %

 CI

Run 1(ppm)

Run 2(ppm)

Run 3(ppm)

Avg.

(ppm) sd

95 %

 CI

Run 1

(%)

Run 2

(%)

Ru

(%

Air Liquide Low 56.25 55.97 55.97 56.1 54.9 0.16 0.19 48.01 48.65 48.42 48.36 0.33 0.37 5.03 5.02 5

Mid 397.05 392.96 395.44 395.1 395.9 2.06 2.33 496.63 496.96 497.92 497.17 0.67 0.76 12.07 12.09 12

High 860.32 859.81 859.40 859.8 889.5 0.46 0.52 985.63 987.67 988.48 987.26 1.47 1.66 18.16 18.15 1

AirgasSouthwestSpecialty Gases

Low 54.71 54.24 54.59 54.5 53.4 0.24 0.27 46.91 47.33 46.77 47.01 0.29 0.33 4.96 4.98 4

Mid 410.74 410.51 409.99 410.4 411.7 0.39 0.44 489.19 492.51 494.61 492.10 2.73 3.09 12.06 12.07 12

High 880.90 880.39 881.25 880.8 912.5 0.43 0.49 989.04 996.04 997.40 994.16 4.49 5.08 18.09 18.10 1

Airgas NCNSpecialty Gases

Low 54.71 54.31 54.02 54.3 53.2 0.34 0.39 49.92 49.93 49.91 49.92 0.01 0.01 5.00 5.00 4

Mid 387.23 386.01 386.62 386.6 387.2 0.61 0.69 499.53 500.07 500.07 499.89 0.31 0.35 12.06 12.08 12

High 836.38 839.38 838.08 837.9 865.5 1.50 1.70 998.85 999.23 1002.75 1000.28 2.15 2.43 18.15 18.15 1

Airgas SouthSpecialty Gases

Low 53.80 54.09 53.69 53.9 52.7 0.21 0.24 50.22 50.25 50.27 50.25 0.02 0.03 5.02 5.00 

Mid 405.78 404.45 403.66 404.6 405.7 1.07 1.21 505.56 505.86 506.24 505.89 0.34 0.39 12.04 12.05 12

High 870.18 869.09 869.75 869.7 900.2 0.55 0.62 1003.10 1005.63 1003.25 1003.99 1.42 1.61 18.19 18.18 1

BOC Gases Low 53.05 52.33 52.50 52.6 51.5 0.38 0.43 50.66 50.44 50.45 50.52 0.13 0.15 4.99 4.97 4

Mid 397.98 398.93 398.98 398.6 399.5 0.56 0.64 499.08 500.22 500.10 499.80 0.63 0.71 12.05 12.06 12

High 838.89 836.86 836.45 837.4 864.9 1.30 1.48 1001.16 1001.68 1001.56 1001.47 0.27 0.31 18.15 18.14 1

AGA(Linde GasGroup)

Low 52.05 52.10 51.99 52.0 51.0 0.06 0.07 48.57 48.64 48.80 48.67 0.12 0.13 5.23 5.23 

Mid 389.75 389.34 389.50 389.5 390.2 0.21 0.23 456.20 463.49 465.56 461.75 4.92 5.57 12.68 12.68 12

High 867.32 866.90 869.00 867.7 898.1 1.11 1.26 953.67 956.23 957.59 955.83 1.99 2.25 18.55 18.53 1

Matheson TriGas Low 52.67 52.55 52.55 52.6 51.5 0.07 0.08 48.14 48.52 48.32 48.33 0.19 0.22 5.00 4.99 4

Mid 402.30 400.02 399.61 400.6 401.6 1.45 1.64 501.68 502.20 504.49 502.79 1.50 1.70 12.07 12.05 12

High 870.68 870.76 871.86 871.1 901.8 0.66 0.75 987.12 997.03 998.70 994.28 6.26 7.08 18.06 18.07 1

Messer MGIndustries

Low 51.59 51.42 51.54 51.5 50.4 0.09 0.10 48.66 49.05 48.95 48.89 0.20 0.23 5.09 5.07 

Mid 396.27 396.12 395.86 396.1 396.9 0.21 0.24 506.05 506.68 506.74 506.49 0.38 0.43 12.23 12.22 12

High 851.47 851.96 851.55 851.7 880.5 0.27 0.30 1015.82 1018.71 1019.49 1018.01 1.93 2.19 18.27 18.27 1

Messer MGIndustries(Spec AirGases)

Low 52.14 51.64 51.76 51.8 50.8 0.26 0.30 47.50 48.35 48.63 48.16 0.59 0.66 5.10 5.09 

Mid 399.24 397.82 398.03 398.4 399.3 0.76 0.86 502.30 503.05 503.46 502.94 0.59 0.66 12.23 12.22 12

High 857.83 857.66 857.00 857.5 886.9 0.44 0.50 1016.29 1019.50 1018.87 1018.22 1.70 1.92 18.31 18.32 1
Table A-4. MACTEC Analysis Data

Gas Vendor

Gas

Conc.

Range

NO Analysis by UV SO2 Analysis by UV CO2 Ana

Run 1(ppm)

Run 2(ppm)

Run 3(ppm)

Avg.

(ppm)

CorrAvg.

(ppm) sd

95 %

 CI

Run 1(ppm)

Run 2(ppm)

Run 3(ppm)

Avg.

(ppm) sd

95 %

 CI

Run 1

(%)

Run 2

(%)

Ru

(%

NationalSpecialty Gases

Low 49.58 49.18 48.80 49.2 48.1 0.39 0.44 50.69 50.49 50.30 50.49 0.19 0.22 4.88 4.87 4

Mid 399.92 400.29 400.93 400.4 401.3 0.51 0.58 495.71 500.33 501.32 499.12 3.00 3.39 11.98 11.97 1

High 897.19 895.81 895.81 896.3 929.4 0.80 0.90 993.36 997.19 996.68 995.74 2.08 2.35 18.31 18.30 1

Praxair Low 53.12 53.12 52.65 53.0 51.9 0.27 0.31 49.75 49.59 49.42 49.59 0.17 0.19 5.03 5.03 

Mid 404.46 403.71 403.91 404.0 405.1 0.39 0.44 503.65 507.03 509.09 506.59 2.75 3.11 12.19 12.17 12

High 894.44 894.52 895.30 894.8 927.8 0.48 0.54 994.02 1005.07 1002.68 1000.59 5.81 6.58 18.05 18.11 1

Scott SpecialtyGases

Low 52.10 52.33 51.76 52.1 51.0 0.29 0.32 48.92 49.14 49.23 49.10 0.16 0.18 5.01 5.01 

Mid 398.45 401.86 401.81 400.7 401.7 1.95 2.21 495.44 497.39 500.07 497.63 2.32 2.63 12.05 12.04 12

High 871.86 871.94 871.94 871.9 902.7 0.05 0.05 996.88 1000.62 1004.44 1000.65 3.78 4.28 18.03 18.03 1

Scott-Marrin,Inc.

Low 52.89 52.78 52.78 52.8 51.7 0.06 0.07 50.96 51.16 51.10 51.07 0.10 0.12 5.09 5.09 

Mid 398.45 398.66 399.87 399.0 399.9 0.76 0.86 502.25 502.78 503.77 502.94 0.77 0.88 12.12 12.11 12

High 872.62 869.75 869.41 870.6 901.2 1.76 1.99 989.94 993.10 995.73 992.92 2.90 3.28 18.15 18.13 1

Spectra Gases,Inc.

Low 52.54 52.15 51.97 52.2 51.1 0.30 0.33 49.05 49.15 49.37 49.19 0.16 0.18 5.02 5.01 

Mid 402.40 403.08 403.90 403.1 404.2 0.75 0.85 492.20 493.33 493.61 493.05 0.75 0.85 12.10 12.09 12

High 887.13 887.64 887.99 887.6 919.9 0.43 0.49 986.48 987.86 988.46 987.60 1.02 1.15 18.09 18.08 1
Table A-5. Spectral Insights’ Analysis Data

Gas Vendor

Gas

Conc.

Range

NO Analysis by FTIR SO2 Analysis by FTIR CO2 Analysis by 

Run 1(ppm)

Run 2(ppm)

Run 3(ppm)

Avg.

(ppm) sd

95 % 

CI

Run 1(ppm)

Run 2(ppm)

Run 3(ppm)

Avg.

(ppm) sd

95 % 

CI

Run 1

(%)

Run 2

(%)

Run 3

(%)

Av

(%

Air Liquide Low 54.10 54.00 53.40 53.8 0.38 0.43 47.91 48.02 47.86 47.93 0.08 0.09 4.999 5.010 4.965 4

Mid 392.40 393.00 392.00 392.5 0.50 0.57 500.8 497.7 497.1 498.5 1.99 2.25 12.05 11.92 11.96 1

High 905.00 906.00 905.00 905.3 0.58 0.65 1005.7 1004.8 1003.1 1004.5 1.32 1.49 17.55 17.47 17.42 1

AirgasSouthwestSpecialty Gases

Low 50.00 50.20 49.60 49.9 0.31 0.35 47.92 47.33 47.30 47.52 0.35 0.40 5.021 4.977 4.953 4

Mid 407.60 405.10 406.30 406.3 1.25 1.41 501.0 501.3 501.8 501.4 0.40 0.46 12.05 12.00 12.12 12

High 927.00 923.00 925.00 925.0 2.00 2.26 1006.4 1008.1 1010.0 1008.2 1.80 2.04 17.80 17.69 17.58 1

Airgas NCNSpecialty Gases

Low 51.20 51.80 51.50 51.5 0.30 0.34 49.71 49.82 49.83 49.79 0.07 0.08 4.968 4.988 4.953 4

Mid 383.70 381.30 382.10 382.4 1.22 1.38 504.0 504.0 504.4 504.1 0.23 0.26 12.13 11.96 12.04 12

High 871.00 870.00 870.00 870.3 0.58 0.65 1006.4 1005.0 1009.0 1006.8 2.03 2.30 17.98 17.89 17.92 1

Airgas SouthSpecialty Gases

Low 51.60 52.00 51.80 51.8 0.20 0.23 50.66 50.52 50.56 50.58 0.07 0.08 5.006 4.992 4.997 4

Mid 402.70 399.20 398.90 400.3 2.11 2.39 507.1 508.1 508.5 507.9 0.72 0.82 12.18 12.19 12.13 12

High 912.00 914.00 911.00 912.3 1.53 1.73 1017.5 1013.3 1017.5 1016.1 2.42 2.74 17.79 17.88 17.93 1

BOC Gases Low 50.60 50.60 50.30 50.5 0.17 0.20 50.99 51.00 50.50 50.83 0.29 0.32 4.980 4.996 4.942 4

Mid 398.00 396.10 398.00 397.4 1.10 1.24 498.5 502.4 498.5 499.8 2.25 2.55 11.99 11.93 11.90 1

High 880.00 876.00 884.00 880.0 4.00 4.53 1014.5 1014.8 1017.5 1015.6 1.65 1.87 17.32 17.45 17.44 1

AGA(Linde GasGroup)

Low 50.60 50.50 50.40 50.5 0.10 0.11 49.56 49.42 49.63 49.54 0.11 0.12 5.146 5.142 5.149 5

Mid 390.00 386.00 389.00 388.3 2.08 2.36 463.0 463.3 466.2 464.2 1.77 2.00 12.48 12.40 12.46 12

High 905.00 903.00 902.00 903.3 1.53 1.73 968.0 966.9 967.1 967.3 0.59 0.66 18.20 18.21 18.23 1

MathesonTri-Gas

Low 50.60 50.60 50.50 50.6 0.06 0.07 49.07 48.86 48.92 48.95 0.11 0.12 4.985 4.977 4.974 4

Mid 398.00 398.00 397.00 397.7 0.58 0.65 503.0 503.1 504.6 503.6 0.90 1.01 11.97 11.91 11.92 1

High 909.00 907.00 905.00 907.0 2.00 2.26 1005.5 1005.8 1008.3 1006.5 1.54 1.74 17.93 17.97 18.02 1

Messer MGIndustries

Low 49.80 50.10 50.10 50.0 0.17 0.20 48.90 49.37 49.51 49.26 0.32 0.36 5.026 5.016 5.027 5

Mid 392.90 390.00 391.00 391.3 1.47 1.67 508.1 508.3 509.1 508.5 0.53 0.60 12.19 12.12 12.22 12

High 891.00 886.00 883.00 886.7 4.04 4.57 1030.1 1030.0 1027.8 1029.3 1.30 1.47 17.69 17.69 17.67 1

Messer MGIndustries(Spec AirGases)

Low 50.40 50.40 50.60 50.5 0.12 0.13 49.32 48.86 49.19 49.12 0.24 0.27 5.063 5.050 5.047 5

Mid 398.50 394.90 394.50 396.0 2.20 2.49 502.3 505.0 504.8 504.0 1.50 1.70 12.15 12.18 12.21 12

High 909.00 901.00 901.00 903.7 4.62 5.23 1026.4 1031.6 1031.4 1029.8 2.95 3.33 17.29 17.27 17.25 1
Table A-5. Spectral Insights’ Analysis Data

Gas Vendor

Gas

Conc.

Range

NO Analysis by FTIR SO2 Analysis by FTIR CO2 Analysis by 

Run 1(ppm)

Run 2(ppm)

Run 3(ppm)

Avg.

(ppm) sd

95 % 

CI

Run 1(ppm)

Run 2(ppm)

Run 3(ppm)

Avg.

(ppm) sd

95 % 

CI

Run 1

(%)

Run 2

(%)

Run 3

(%)

Av

(%

NationalSpecialty Gases

Low 48.60 48.10 48.10 48.3 0.29 0.33 50.45 50.72 50.76 50.64 0.17 0.19 4.905 4.897 4.853 4

Mid 399.10 397.10 395.70 397.3 1.71 1.93 499.0 503.5 504.2 502.2 2.82 3.19 12.04 12.14 12.11 12

High 945.00 957.00 941.00 947.7 8.33 9.42 1013.7 1012.1 1007.3 1011.0 3.33 3.77 17.74 17.87 17.87 1

Praxair Low 52.00 51.20 51.30 51.5 0.44 0.49 50.37 50.66 50.06 50.36 0.30 0.34 4.980 5.000 4.978 4

Mid 401.60 400.30 399.80 400.6 0.93 1.05 510.8 511.8 512.3 511.6 0.76 0.86 12.22 12.24 12.21 12

High 933.00 933.00 932.00 932.7 0.58 0.65 1009.6 1007.1 1009.4 1008.7 1.39 1.57 17.84 17.83 17.86 1

Scott SpecialtyGases

Low 50.30 50.70 49.90 50.3 0.40 0.45 50.34 50.46 50.33 50.38 0.07 0.08 4.998 4.996 4.966 4

Mid 401.00 395.90 394.80 397.2 3.31 3.74 501.2 503.5 504.4 503.0 1.65 1.87 12.15 12.20 12.18 12

High 921.00 917.00 917.00 918.3 2.31 2.61 1020.5 1021.7 1021.7 1021.3 0.69 0.78 17.22 17.19 17.19 1

Scott-Marrin,Inc.

Low 51.60 51.70 52.00 51.8 0.21 0.24 51.17 51.29 51.06 51.17 0.12 0.13 5.072 5.051 5.016 5

Mid 396.10 395.30 395.00 395.5 0.57 0.64 507.5 508.2 507.8 507.8 0.35 0.40 12.14 12.03 12.05 12

High 902.60 898.50 895.00 898.7 3.80 4.30 995.7 997.1 995.0 995.9 1.07 1.21 18.05 18.03 18.06 1

Spectra Gases,Inc.

Low 50.80 50.80 50.80 50.8 0.00 0.00 49.96 49.85 49.65 49.82 0.16 0.18 5.016 4.989 5.004 5

Mid 402.40 400.40 399.40 400.7 1.53 1.73 492.3 492.9 494.1 493.1 0.92 1.04 12.26 12.24 12.24 12

High 935.00 930.00 936.00 933.7 3.21 3.64 999.8 992.9 1002.7 998.5 5.03 5.70 17.33 17.23 17.30 1