EPA Protocol Gas Audit Results

Tri-Blend NO/SO2/CO2 Gases - Certified According to EPA Traceability Protocol

EPA Cylinder Gas Assays: April 2003 - February 2004

Tag Reported Tag Reported

Value Uncert. NO Uncert. 95% CI Relative CI Orig Tag Re-analysis NO 95% CI Relative CI Orig Tag Re-analysis Value Uncert. SO2 Uncert. 95% CI Relative CI Orig Tag

(ppm NO) (+/-) (ppm) (+/- ppm) (ppm) (%) (% diff) (% diff) (ppm) (ppm) (%) (% diff) (% diff) (ppm SO2) (+/-) (ppm) (+/- ppm) (ppm) (%) (% diff)

1 Low 54.0 0.8 ppm FTIR GMIS 54.9 1.3 0.2 0.34 -1.6 53.83 0.43 0.80 0.3 47.5 0.8 ppm FTIR GMIS 48.36 2.88 0.37 0.76 -1.8

2 Mid 401 5 ppm FTIR GMIS 395.9 3.0 2.3 0.59 1.3 392.5 0.6 0.15 2.2 499 4 ppm FTIR GMIS 497.17 3.13 0.76 0.15 0.4

3 High 911 10 ppm FTIR GMIS (b) --- --- --- --- 905 1 0.07 0.7 981 9 ppm FTIR GMIS 987.26 3.29 1.66 0.17 -0.6

1 Low 48.90 1% 49.89 (e) 2.0 Chem NTRM 53.4 1.9 0.3 0.51 -8.4 -6.5 49.93 0.35 0.70 -2.1 -0.1 47.73 1% 47.62 -0.2 NDIR NTRM 47.01 2.88 0.33 0.70 1.5

2 Mid 406.0 1% 405.2 -0.2 Chem NTRM 411.7 3.1 0.4 0.11 -1.4 -1.6 406.3 1.5 0.36 -0.1 -0.3 496.8 1% 500.9 0.8 NDIR NTRM 492.10 3.13 3.09 0.63 1.0

3 High 900.0 1% 909.8 (e) 1.1 Chem NTRM (b) --- --- --- --- --- 925 2 0.24 -2.7 -1.6 994.6 1% 1003 0.8 NDIR NTRM 994.16 3.96 5.08 0.51 0.0

1 Low 51.4 1% 52.21 1.6 NDIR NTRM 53.2 1.3 0.4 0.73 -3.4 -1.9 51.50 0.34 0.66 -0.2 1.4 50.4 1% 50.05 -0.7 NDIR GMIS 49.92 2.93 0.01 0.02 1.0

2 Mid 388 1% 384.6 -0.9 NDIR NTRM 387.2 3.0 0.7 0.18 0.2 -0.7 382.4 1.4 0.36 1.5 0.6 500 1% 504.3 0.9 NDIR NTRM 499.89 3.17 0.35 0.07 0.0

3 High 845 1% 860.9 (e) 1.9 NDIR NTRM (b) --- --- --- --- --- 870 1 0.07 -2.9 -1.0 1000 1% 1002 0.2 NDIR NTRM 1000.28 3.96 2.43 0.24 0.0

1 Low 50.05 1% 51.69 (e) 3.3 Chem GMIS 52.7 1.3 0.2 0.45 -5.1 -2.0 51.80 0.23 0.44 -3.4 -0.2 50.23 1% 51.03 1.6 NDIR NTRM 50.25 2.88 0.03 0.05 0.0

2 Mid 397.5 1% 401 0.9 Chem NTRM 405.7 3.0 1.2 0.30 -2.0 -1.2 400.3 2.1 0.52 -0.7 0.2 502.8 1% 509.2 1.3 NDIR NTRM 505.89 3.14 0.39 0.08 -0.6

3 High 900.0 1% 900.8 0.1 Chem NTRM (b) --- --- --- --- --- 912 2 0.19 -1.3 -1.2 998.8 1% 1012 1.3 NDIR NTRM 1003.99 4.01 1.61 0.16 -0.5

1 Low 49.8 1% FTIR SRM 51.5 1.3 0.4 0.83 -3.3 50.50 0.20 0.40 -1.4 50.9 1% FTIR SRM 50.52 2.70 0.15 0.29 0.8

2 Mid 407.8 1% 406.0 (f) -0.4 FTIR SRM 399.5 3.0 0.6 0.16 2.1 1.6 397.4 1.1 0.27 2.6 2.2 500.4 1% FTIR NTRM 499.80 3.13 0.71 0.14 0.1

3 High 900 1% 896 (f) -0.4 FTIR SRM (b) --- --- --- --- --- 880 5 0.51 2.3 1.8 1000 1% FTIR NTRM 1001.47 3.96 0.31 0.03 -0.1

1 Low 50.4 0.5 ppm Chem GMIS 51.0 1.3 0.1 0.13 -1.1 50.50 0.11 0.22 -0.2 48.7 0.5 ppm NDIR GMIS 48.67 2.70 0.13 0.28 0.1

2 Mid 396 4 ppm Chem GMIS 390.2 2.4 0.2 0.06 1.5 388.3 2.4 0.61 2.0 466 5 ppm NDIR GMIS 461.75 3.04 5.57 1.21 0.9

3 High 904 9 ppm Chem GMIS (b) --- --- --- --- 903 2 0.19 0.1 956 10 ppm NDIR GMIS 955.83 3.87 2.25 0.24 0.0

1 Low 48.9 0.4 ppm 50.4 (g) 3.1 FTIR SRM 51.5 1.3 0.1 0.15 -5.0 -2.1 50.57 0.07 0.14 -3.3 -0.3 49.5 0.4 ppm FTIR SRM 48.33 2.76 0.22 0.45 2.4

2 Mid 410 1 ppm 405.1 (g) -1.2 FTIR SRM 401.6 3.0 1.6 0.41 2.1 0.9 397.7 0.7 0.16 3.1 1.9 504 5 ppm FTIR SRM 502.79 3.04 1.70 0.34 0.2

3 High 904 9 ppm FTIR SRM (b) --- --- --- --- 907 2 0.25 -0.3 988 9 ppm FTIR SRM 994.28 5.30 7.08 0.71 -0.6

1 Low 50.0 0.128 ppm Chem GMIS 50.4 1.3 0.1 0.20 -0.9 50.00 0.20 0.40 0.0 50.1 0.507 ppm NDIR GMIS 48.89 2.70 0.23 0.46 2.5

2 Mid 398 1.28 ppm Chem GMIS 396.9 3.0 0.2 0.06 0.3 391.3 1.7 0.43 1.7 501 1.82 ppm NDIR GMIS 506.49 3.09 0.43 0.09 -1.1

3 High 888 2.99 ppm Chem GMIS (b) --- --- --- --- 887 5 0.52 0.1 1004 3.1 ppm NDIR GMIS 1018.01 5.36 2.19 0.21 -1.4

1 Low 50.0 0.131 ppm Chem GMIS 50.8 1.3 0.3 0.58 -1.5 50.47 0.13 0.26 -0.9 49.3 0.506 ppm NDIR GMIS 48.16 2.70 0.66 1.38 2.4

2 Mid 403 1.28 ppm Chem GMIS 399.3 2.5 0.9 0.22 0.9 396.0 2.4 0.62 1.8 496 1.82 ppm NDIR GMIS 502.94 3.04 0.66 0.13 -1.4

3 High 894 2.99 ppm Chem GMIS (b) --- --- --- --- 904 5 0.58 -1.1 1004 3.1 ppm NDIR GMIS 1018.22 5.40 1.92 0.19 -1.4

1 Low 46.2 1% 47.3 (h) 2.4 FTIR GMIS 48.1 1.3 0.4 0.92 -4.0 -1.8 48.27 0.33 0.68 -4.3 -2.0 51.8 1% 51.5 (h) -0.6 FTIR GMIS 50.49 2.75 0.22 0.44 2.6

2 Mid 398 1% FTIR GMIS 401.3 2.5 0.6 0.14 -0.8 397.3 1.9 0.48 0.2 500 1% FTIR GMIS 499.12 3.04 3.39 0.68 0.2

3 High 930 1% 930 0.0 FTIR GMIS (b) --- --- --- --- 948 9 0.99 -1.9 991 1% 992 0.1 FTIR GMIS 995.74 5.30 2.35 0.24 -0.5

1 Low 51.2 1% Chem GMIS 51.9 1.3 0.3 0.59 -1.3 51.50 0.49 0.95 -0.6 50.0 1% UV GMIS 49.59 2.75 0.19 0.38 0.8

2 Mid 406 1% NDIR GMIS 405.1 2.5 0.4 0.11 0.2 400.6 1.00 0.25 1.3 509 1% NDIR GMIS 506.59 2.83 3.11 0.61 0.5

3 High 914 1% NDIR GMIS (b) --- --- --- --- 933 1 0.07 -2.0 999 1% NDIR GMIS 1000.59 5.31 6.58 0.66 -0.2

1 Low 50.0 1% FTIR NTRM 51.0 1.3 0.3 0.63 -1.9 50.30 0.45 0.89 -0.6 50.4 1% FTIR NTRM 49.10 2.81 0.18 0.38 2.7

2 Mid 402 1% FTIR NTRM 401.7 2.5 2.2 0.55 0.1 397.2 3.7 0.94 1.2 503 1% FTIR NTRM 497.63 2.83 2.63 0.53 1.1

3 High 911 1% FTIR NTRM (b) --- --- --- --- 918 3 0.28 -0.8 1011 1% FTIR NTRM 1000.65 3.83 4.28 0.43 1.0

1 Low 50.8 0.3 ppm Chem GMIS 51.7 1.3 0.1 0.14 -1.8 51.77 0.24 0.46 -1.9 50.9 0.6 ppm UV GMIS 51.07 2.75 0.12 0.23 -0.3

2 Mid 397 2 ppm Chem GMIS 399.9 2.5 0.9 0.22 -0.7 395.5 0.7 0.16 0.4 504 5 ppm UV GMIS 502.94 2.87 0.88 0.17 0.2

3 High 886 5 ppm Chem GMIS (b) --- --- --- --- 899 4 0.48 -1.4 997 10 ppm UV GMIS 992.93 3.81 3.28 0.33 0.4

1 Low 50.1 1% Chem NTRM 51.1 1.3 0.3 0.65 -2.0 50.80 0.00 0.00 -1.4 50.2 1% NDIR NTRM 49.19 2.75 0.18 0.37 2.1

2 Mid 405 1% FTIR NTRM 404.2 2.5 0.8 0.21 0.2 400.8 1.7 0.43 1.0 495 1% NDIR GMIS 493.05 2.83 0.85 0.17 0.4

3 High 923 1% FTIR NTRM (b) --- --- --- --- 934 4 0.39 -1.2 988 1% NDIR GMIS 987.60 3.85 1.15 0.12 0.0

(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 monitor setup performed by the manufacturer was not optimum for the 1000 ppm range.

(c) High-range gas cylinder was returned to Air Liquide for CO2 reanalysis. Vendor reported a new CO2 value (on May 6, 2004) of 17.9%, which differs by less than 2.0% from the EPA-determined value. Reanalyzed value is also within +/- 2.0% of original tag value. No corrective action taken by the vendor.

(d) The high-level CO2 evaluations were based solely on the NDIR results because there was not enough high-level CO2 SRM or NTRM to provide reference spectra for the FTIR.

(e) Gas cylinders were returned to Airgas for NO reanalyses. Vendor reported new NO values on April 26, 2004, which differ by less than 2.0% from the corresponding EPA-determined values. In all but one case, the reanalyzed value was within +/- 2.0% of original tag value. No corrective action taken by the vendor.

(f) Mid- and high-level gas cylinders were returned to BOC Gases for NO reanalyses. Vendor reported new values on June 9, 2004, which differ by less than 2.0% from the corresponding EPA-determined UV or FTIR values. The two reanalyzed NO values also differ by less than 2.0% of original tag value. No corrective action was taken.

(g) Gas cylinders were returned to Matheson for NO and CO2 reanalyses. Vendor reported new values on May 10, 2004, which differ by less than 2.0% from the corresponding EPA-determined values. Two of the three reanalyzed values differed by more than 2.0% of original tag value. The corrected concentrations for NO were done by a shift to a wavenumber within a spectral region where CO2 interference is min

(h) Gas cylinders were returned to National Specialty Gases for NO, SO2, and CO2 reanalyses. Vendor reported new values on May 10, 2004, which differ by less than 2.0% from the corresponding EPA-determined values. Two of the three reanalyzed values differed by more than 2.0% of original tag value. As a result of the audit, National Specialty Gases recalibrated their FTIR and obtained a more experienced, a

(i) High-range gas cylinder was returned to Praxair for CO2 reanalysis based on an initial EPA finding of 18.07% CO2. Vendor reported a new CO2 value (on May 27, 2004) of 17.82%. Vendor had independent 3rd party (Scott Marin) analyze the cylinder, resulting in 17.77% CO2. Vendor had the National Institute of Standards and Technology (NIST) analyze cylinder, resulting in 17.85% CO2. All of the reanalyzed va

of the analytical capabilities of individual producers. EPA presents this information without assigning a rating to the gas vendors, for example, who is the best, who is approved, or who is not approved.

% Change in 

Vendor 

Certified 

Value

Analysis by UV (a)

SO2 Component

Analysis by UV

NO Component

% Change 

in Vendor 

Certified 

Value

Vendor 

Analytical 

Technique

Reference 

Standard

Reanalyzed 

Value 

(ppm)

Vendor 

Analytical 

Technique

Reference 

Standard

Airgas NCN Specialty 

Gases

Airgas South Specialty 

Gases

BOC Gases

AGA (Linde Gas Group)

Messer MG Industries 

(Spec Air Specialty 

Gases)

Matheson Tri-Gas

Messer MG Industries

Gas Vendor

Cyl. 

No.

Analysis by FTIR

Scott-Marrin In.

Air Liquide

Airgas Southwest 

Specialty Gases

Gas 

Conc. 

Range

Re-analyzed 

Value (ppm)

National Specialty 

Gases

Spectra Gases Inc.

Praxair

Scott Specialty Gases

If the difference between EPA’s value and a gas vendor’s value differs by ±2.0% or less, then (because of the uncertainties in the total measurement system) statistically there is no difference between the two values. Thus, 

a difference of 2.0% would be interpreted as being equal to one of, for example, 0.4%. Any accuracy assessment is an instantaneous snapshot of the process being measured. These results should not be regarded as a final statement

concerning the accuracy of EPA Protocol Gases. They can be used as an indicator of the current status of the accuracy of EPA Protocol Gases as a whole. However, individual results should not be taken as definitive indicators
Tag Reported

Re-analysis SO2 95% CI Relative CI Orig Tag Re-analysis Value Uncert. CO2 Uncert. 95% CI Relative CI Orig Tag Re-analysis CO2 95% CI Relative CI Orig Tag Re-analysis

(% diff) (ppm) (ppm) (%) (% diff) (% diff) (% CO2) (+/-) (%) (+/- % CO2) (% CO2) (%) (% diff) (% diff) (%) (% CO2) (%) (% diff) (% diff)

47.93 0.09 0.19 -0.9 4.97 0.06% CO2 FTIR GMIS 5.02 0.07 0.01 0.12 -1.0 4.991 0.027 0.54 -0.4 Yes

498.5 2.3 0.45 0.1 12.1 0.1% CO2 FTIR GMIS 12.09 0.11 0.02 0.18 0.1 11.98 0.08 0.63 1.0 Yes

1004.5 1.5 0.15 -2.3 17.7 0.2% CO2 17.9 (c) 1.1 FTIR NTRM 18.15 0.17 0.01 0.08 -2.5 -1.4 (d) --- --- --- --- Yes

1.3 47.52 0.40 0.84 0.4 0.2 5.011 1% 5.045 0.7 NDIR NTRM 4.97 0.07 0.01 0.26 0.8 1.5 4.984 0.039 0.78 0.5 1.2 Yes

1.8 501.3 0.5 0.09 -0.9 -0.1 12.0 1% 11.95 -0.4 NDIR NTRM 12.07 0.11 0.01 0.11 -0.6 -1.0 12.06 0.07 0.56 -0.5 -0.9 Yes

0.9 1008.2 2.0 0.20 -1.3 -0.5 17.99 1% 17.97 -0.1 NDIR NTRM 18.09 0.17 0.01 0.04 -0.6 -0.7 (d) --- --- --- --- Yes

0.3 49.79 0.08 0.16 1.2 0.5 5.01 1% 5.064 1.1 NDIR NTRM 5.00 0.07 0.01 0.10 0.2 1.3 4.970 0.020 0.40 0.8 1.9 Yes

0.9 504.2 0.3 0.05 -0.8 0.0 12.0 1% 11.94 -0.5 NDIR NTRM 12.07 0.11 0.01 0.09 -0.6 -1.1 12.04 0.10 0.84 -0.3 -0.8 Yes

0.2 1006.8 2.3 0.23 -0.7 -0.5 18.0 1% 18.06 0.3 NDIR NTRM 18.15 0.17 0.00 0.01 -0.8 -0.5 (d) --- --- --- --- Yes

1.6 50.58 0.08 0.16 -0.7 0.9 5.041 1% 5.057 0.3 NDIR NTRM 5.01 0.07 0.01 0.22 0.7 1.0 4.998 0.008 0.16 0.9 1.2 Yes

0.7 507.9 0.8 0.16 -1.0 0.3 12.0 1% 11.88 -1.0 NDIR NTRM 12.05 0.11 0.01 0.09 -0.4 -1.4 12.17 0.04 0.30 -1.4 -2.4 Yes

0.8 1016.1 2.7 0.27 -1.7 -0.4 18.07 1% 18.15 0.4 NDIR NTRM 18.18 0.17 0.02 0.11 -0.6 -0.2 (d) --- --- --- --- Yes

50.83 0.32 0.63 0.1 5.0 1% FTIR NTRM 4.98 0.07 0.01 0.22 0.5 4.973 0.031 0.62 0.5 Yes

499.8 2.6 0.51 0.1 11.98 1% FTIR NTRM 12.05 0.11 0.01 0.06 -0.6 11.94 0.05 0.44 0.3 Yes

1015.6 1.9 0.18 -1.5 18.02 1% FTIR NTRM 18.14 0.17 0.01 0.06 -0.7 (d) --- --- --- Yes

49.54 0.12 0.24 -1.7 5.2 0.5% CO2 NDIR NTRM/GMIS 5.22 0.07 0.01 0.17 -0.5 5.146 0.004 0.08 1.0 Yes

464.2 2.0 0.43 0.4 12.5 0.1% CO2 NDIR NTRM/GMIS 12.68 0.12 0.01 0.04 -1.4 12.45 0.05 0.38 0.4 Yes

967.3 0.7 0.07 -1.2 18.3 0.2% CO2 NDIR NTRM/GMIS 18.53 0.17 0.02 0.08 -1.2 (d) --- --- --- Yes

48.95 0.12 0.25 1.1 5.23 0.05% CO2 4.94 (g) -5.5 FTIR SRM 4.99 0.07 0.01 0.28 4.8 -1.0 4.979 0.006 0.12 5.0 -0.8 Yes

503.6 1.0 0.20 0.1 12.2 0.1% CO2 FTIR SRM 12.06 0.11 0.01 0.11 1.2 11.93 0.04 0.30 2.3 Yes

1006.5 1.7 0.17 -1.8 17.9 0.1% CO2 FTIR SRM 18.07 0.17 0.00 0.02 -0.9 (d) --- --- --- Yes

49.26 0.36 0.73 1.7 5.05 0.0444% CO2 NDIR GMIS 5.08 0.07 0.01 0.23 -0.5 5.023 0.007 0.14 0.5 Yes

508.5 0.6 0.11 -1.5 12.1 0.0501% CO2 NDIR GMIS 12.22 0.11 0.02 0.13 -1.0 12.18 0.06 0.49 -0.7 Yes

1029.3 1.5 0.14 -2.5 18.2 0.0501% CO2 NDIR GMIS 18.27 0.17 0.00 0.02 -0.4 (d) --- --- --- Yes

49.12 0.27 0.55 0.4 5.07 0.04444% CO2 NDIR GMIS 5.09 0.07 0.01 0.12 -0.5 5.053 0.010 0.20 0.3 Yes

504.0 1.7 0.34 -1.6 12.1 0.0501% CO2 NDIR GMIS 12.22 0.11 0.01 0.10 -1.0 12.18 0.04 0.30 -0.7 Yes

1029.8 3.3 0.32 -2.5 18.3 0.0501% CO2 NDIR GMIS 18.31 0.17 0.00 0.01 -0.1 (d) --- --- --- Yes

2.0 50.64 0.19 0.38 2.3 1.7 4.9 1% 4.9 0.0 FTIR GMIS 4.87 0.06 0.01 0.11 0.5 4.885 0.032 0.66 0.3 Yes

502.2 3.2 0.64 -0.4 12.0 1% FTIR GMIS 11.97 0.11 0.01 0.08 0.3 12.09 0.06 0.48 -0.7 Yes

1011.0 3.8 0.37 -2.0 17.8 1% 18.23 (h) 2.4 FTIR GMIS 18.30 0.17 0.01 0.04 -2.8 -0.4 (d) --- --- --- --- Yes

50.36 0.34 0.68 -0.7 5.00 1% NDIR GMIS 5.03 0.06 0.00 0.05 -0.6 4.986 0.014 0.28 0.3 Yes

511.6 0.9 0.17 -0.5 12.18 1% NDIR GMIS 12.17 0.11 0.02 0.16 0.1 12.23 0.02 0.12 -0.4 Yes

1008.7 1.6 0.16 -1.0 17.59 1% 17.82 (i) 1.3 NDIR GMIS 17.85 0.13 0.01 0.06 -1.5 -0.2 (d) --- --- --- --- Yes

50.38 0.08 0.16 0.0 5.04 1% FTIR NTRM 5.01 0.06 0.00 0.03 0.6 4.987 0.020 0.40 1.1 Yes

503.0 1.9 0.37 0.0 12.10 1% FTIR NTRM 12.04 0.11 0.01 0.07 0.5 12.18 0.03 0.25 -0.7 Yes

1021.3 0.8 0.08 -1.0 17.97 1% FTIR NTRM 18.03 0.17 0.01 0.07 -0.3 (d) --- --- --- Yes

51.17 0.13 0.26 -0.5 5.11 0.05% CO2 GC GMIS 5.09 0.06 0.00 0.03 0.4 5.046 0.032 0.63 1.3 Yes

507.9 0.4 0.08 -0.8 12.02 0.02% CO2 GC GMIS 12.11 0.11 0.01 0.07 -0.7 12.07 0.07 0.55 -0.4 Yes

995.9 1.2 0.12 0.1 17.92 0.05% CO2 GC GMIS 18.13 0.17 0.02 0.12 -1.2 (d) --- --- --- Yes

49.82 0.18 0.36 0.8 5.02 1% NDIR GMIS 5.01 0.06 0.01 0.13 0.1 5.003 0.015 0.30 0.3 Yes

493.1 1.0 0.21 0.4 12.03 1% NDIR NTRM 12.10 0.11 0.01 0.07 -0.5 12.24 0.01 0.10 -1.7 Yes

998.5 5.7 0.57 -1.1 18.07 1% NDIR NTRM 18.08 0.17 0.01 0.05 0.0 (d) --- --- --- Yes

erference 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.

e experienced, analyst.

he reanalyzed values differ by less than 2.0% from the EPA-determined value. The original tag value is within +/- 2.0% of each of the reanalyzed values. The original tag value and the vendor reanalyzed value are within +/- 2.0% of the NIST-generated "true" value. Therefore no corrective action is required.

CO2 Component

Analysis by FTIR

Re-analyzed 

Value (%)

% Change in 

Vendor 

Certified 

Value

Supplied Complete 

Documentation

Vendor 

Analytical 

Technique

Reference 

Standard

Analysis by FTIR Analysis by NDIR