ANALYSIS OF PROTOCOL GASES

An On-Going Quality Assurance Audit
(Results Through March 1995)

Avis P. Hines
Quality Assurance Support Branch
Quality Assurance and Technical Support Division
Atmospheric Research and Exposure Assessment Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
 1.0  INTRODUCTION

     The Atmospheric Research and Exposure Assessment Laboratory
(AREAL) of the U.S. Environmental Protection Agency (EPA)
operates a nationwide audit on the vendors of Protocol Gas
Standards.  The intent of this program is as follows:
     1.   Increase the acceptance and use of Protocol Gases as
          secondary standards by the air monitoring community.
     2.   Provide a quality assurance check for the vendors of 
          these gases. 
     3.   Assist users of Protocol Gases to identify vendors who
          can consistently provide accurately certified Protocol
          Gases.
     For the first audits of nitric oxide, carbon monoxide, and
sulfur dioxide, gas cylinders obtained through third parties were
analyzed in triplicate by EPA and by a non-EPA laboratory.  Each
laboratory used its own SRMs and followed the Protocol Gas
certification procedure.  Because a statistical analysis showed
that the results from EPA and the independent laboratory were
indistinguishable, EPA is now the primary auditing laboratory.
The other laboratory serves as the referee laboratory to resolve
differences between EPA and the vendors.

2.0  PROCEDURE
     Either directly or through third parties, EPA procures
Protocol Gases from commercial sources, checks the accuracy of
the vendors' certification of concentration, and examines the
accompanying documentation for completeness and accuracy. The
vendors are not aware that EPA is obtaining the gases for a check
on the completeness of the documentation and accuracy of the
certification of concentration.
     Protocol Gases have a maximum allowable deviation of 
2% from the certified value.  Accuracy of the certification is
checked using Standard Reference Materials (SRMs).  If the
difference between the EPA-determined and the vendor-determined
concentration is more than 2%, or if the documentation is
incomplete, EPA notifies the vendor immediately to resolve and
correct the problem.
     Results of EPA certification checks are placed on two
bulletin boards, EMTIC (Emission Measurement Technology
Information Center) and AMTIC (Ambient Monitoring Technology
Information Center), of the Technology Transfer Network of the
EPA Office of Air Quality Planning and Standards.     
     Bulletin board entries are organized in tables by gas
mixture type and by vendor. Numerical data are supplemented by
narrative footnotes explaining the results of any corrective
action taken by the vendor.  Thus the entries provide a
continuous record of all audit activities.
     Users who believe that their Protocol Gas has been certified
incorrectly are encouraged to contact Ms. Avis Hines of AREAL
(919-541-4001) to request an EPA certification check.  If EPA
accepts the gas cylinder for testing, the results of these tests
will also be posted on the bulletin boards.

3.0  REQUIRED DOCUMENTATION
     The Protocol Gas procedure specifies two types of
documentation that must accompany the gas cylinder:  a
Certificate of Analysis, which may be mailed separately or
attached to the cylinder; and a cylinder tag which must be
attached to the valve under the valve cap.  Documentation is
incomplete until the vendor provides every item shown in Tables A
and B for the certificate and the tag, respectively. These tables
reflect the requirements specified in the revised Protocol Gas
guidance issued by this Laboratory in September 1993 (U.S. EPA
Traceability Protocol for Assay and Certification of Gaseous
Calibration Standards (Revised September 1993), EPA 600/R03/224).

Table A.  REQUIRED DOCUMENTATION FOR A CERTIFICATE OF ANALYSIS    
                              
     Cylinder ID number            Reference standard data 

     Certified concentration       Protocol statement
     of analyte

     Balance gas                   Analytical method used in
                                   assay  

     Cylinder pressure             All analyzer readings

     Certificate date              Calculations to three 
                                   significant figures
  
     Expiration date               Name and signature of     
                                   analyst and laboratory name

     Certification period 
     (months)  

TABLE B.  REQUIRED DOCUMENTATION FOR A CYLINDER TAG  
 
     Cylinder ID number              Certification date

     Expiration date                 Protocol statement 

     Laboratory ID                   Balance gas

     Cylinder pressure               Analyte Concentration 

4.0  RESULTS  
     This section of the audit report, organized by gas mixtyre
type and by vendor, is updated whenever EPA conducts a new audit
or receives corrective action reports from a vendor.  It allows
users of Protocol Gases to easily review the comparative
performances of the vendors.
     The standard of comparison used in reporting the
certification of concentration check results is the relative
percent difference between the vendor and the EPA values. Prior
to this latest update only single component gases had been
checked.  With the inclusion of multi-component gases the
reporting format used previously became unwieldy.  Therefore, the
tables were simplified to ensure they still provided information
in a user-friendly form. This was accomplished by: (1) removing
the vendor and the EPA concentration values from the tables and
reporting the nominal value to the nearest 10 ppm; and (2)
removing the cost information. (Since the prices of Protocol
Gases are subject to change and differ markedly between vendors,
users of these gases should obtain them through a competitive
procurement procedure whenever possible.) 
     The tables summarize audit results for each gas mixture type
and include footnotes which describe corrective actions taken by
the vendors.  In each table each vendor has been assigned an
acronym and a footnote letter.  If a vendor has more than one
plant, each plant is assigned its own acronym and footnote. 
Notes may not be necessary for every vendor on every audit.  The
following acronyms have been assigned to each vendor:

     ACRONYM                  VENDOR

     AGA, OH             AGA Gas, Inc.
                         Maumee, OH     

     APC-NC              Air Prod. and Chem
                         Durham, NC

     APC-IL              Air Prod. and Chem
                         Chicago, IL
 
     AIG-MI              Airco Industrial Gases
                         Royal Oak, MI
     
     AIG-NC              Airco Industrial Gases
                         Research Triangle Park, NC

     AIG-NJ              Airco Industrial Gases
                         Riverton, NJ

     ASG-PA              Alphagaz Spec. Gas Div.
                         Morrisville, PA

     ASG-CA              Alphagaz Spec. Gas Div.
                         Long Beach, CA

     
     MGP-OH              Matheson Gas Products
                         Twinsburg, OH

     LCC                 Liquid Carbonic Cylinder Gas Products
                         Bethlehem, PA

     MGP-NJ              Matheson Gas Products
                         East Rutherford, NJ

     MGI-PA              MG Industries Gas Prod.
                         Valley Forge, PA

     NSG-NC              National Specialty Gases
                         Durham, NC

     SMG-CA              Scott Marrin Gases
                         Riverside, CA

     SSG-NC              Scott Specialty Gases
                         Durham, NC

     SSG-NJ              Scott Specialty Gases
                         Plainille, NJ

     SSG-PA              Scott Specialty Gases
                         Plumsteadville, PA

     When using the data in the following tables for procuring
Protocol Gases readers should bear in mind the following points. 
First, the information in the footnotes may be important and
should not be ignored.  Second, if the difference between EPA's
value and a manufacturer's value differs by 2% 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% is the same as one of 0.57%.  Third,
EPA has not assigned a rating to the vendors concerning who is
the best, who is approved, who is not approved, etc.  The
information is presented without making such judgments.

                     TABLE I.  NO Protocol Gas Results

            Nominal
            ppm      Date        Date     % Difference   Complete
Vendor      NO       Certified   Checked  (Vendor-EPA)   Doc.     Notes

APC-NC      40       4-92        7-92        2.0         Yes       

AIG-MI      40       5-92        7-92       -0.5         No        a

ASG-PA      40       4-92        7-92       -0.7         No        b

MGP-NJ      40       4-92        7-92        0.7         No        c

MGI-PA      40       4-92        7-92        0.2         No        d

NSG-NC      40       4-92        7-92       -1.7         Yes

SMG-CA      40       4-92        7-92        0.0         Yes

SSG-NC      40       4-92        7-92       -0.7         No        e

a.  Documentation problems corrected.
b.  Documentation problems corrected.
c.  Documentation problems corrected.
d.  Documentation problems corrected.
e.  Documentation problems corrected.

                     TABLE II.  SO2 Protocol Gas Results

            Nominal
            ppm      Date        Date     % Difference   Complete
Vendor      SO2      Certified   Checked  (Vendor-EPA)   Doc.     Notes

APC-NC      50        9-92       12-92       -3.8        No          a

AIG-NJ      50        9-92       12-92       -0.7        No          b

AIG-NC      50        6-93        7-93        1.3        Yes

AGA-OH      20        7-92        7-93        0.8        Yes

ASG-PA      50        8-92       12-92        1.1        No          c

MGP-OH      50        9-92       12-92       -3.9        No          d

MGP-NJ      50        5-93        5-93        3.1        Yes         i

MGI-PA      50       12-92        2-93       -5.5        No          e
MGI-PA      99        8-94        2-95       -0.8        Yes

NSG-NC      50        8-92       12-92       -3.6        Yes         f

SMG-CA      50        8-92       12-92       -0.2        No          g
SMG-CA     100       10-92        9-93        1.1        Yes

SSG-NC      50        7-92       12-92        0.6        Yes

SSG-NJ      50        7-93        5-94        0.4        No          h
   
a.  Vendor replaced calibration standard and reported (3/93) new value of  
    50.2 ppm (-1% difference).  Documentation problems corrected.
b.  Prior to receiving EPA results, vendor notified all recent purchasers   
    that Airco's calibration standard was defective and requested gas be    
    returned for re-analysis at no cost.
c.  Documentation problems corrected.
d.  Vendor replaced calibration standard and reported (2/93) new value of  
    56.8 ppm (0.7% difference).  Documentation problems corrected.
e.  Vendor found error on part of analyst (3/93).  Analyst given additional 
    training.  Documentation problems corrected.
f.  Vendor replaced calibration standard.  No re-analysis done             
    Documentation problems corrected.
g.  Documentation problems corrected.
h.  Documentation problems corrected.
i.  Vendor replaced pulsed fluorescence detector with a NDIR detector and 
       reported a new value of 52.6 ppm (1.3% difference).

                     TABLE III.  CO Protocol Gas Results

            Nominal
            ppm      Date        Date     % Difference   Complete
Vendor      CO    Certified   Checked  (Vendor-EPA)   Doc.     Notes

APC-NC      40        1-93       4-93            0.3      No         a

AIG-NJ      40        1-93       4-93           -0.3      No         

APC-IL       9       12-94       2-95           -0.8      Yes

ASG-PA      40        1-93       4-93           -0.7      Yes

MGP-OH      40        1-93       4-93            0.3      No         b

MGP-NJ      40        5-93       6-93           -0.6      Yes

MGI-PA      40        1-93       4-93           -1.2      No         c

NSG-NC      40       12-92       4-93            1.0      No         d

SMG-CA      40        1-93       4-93           -0.5      Yes

SSG-NC      40        1-93       4-93            0.0      Yes

a. Certificate missing; sent when EPA requested but did not agree with
   cylinder tag; second certificate matched cylinder tag but calibration
   standard identified as having gone out of calibration in January 1992;
   sent third certificate with corrected calibration date.
b. Certificate sent only after EPA requested it.
c. Documentation problems corrected.
d. Certified only for six months rather than the 24 months allowed.

               TABLE IV.  Mixture NO/SO2 Protocol Gas Results

   Note:  The first group of multi-blend Protocol Gases was checked
November 1993 through May 1994.  The results are listed in Table IV. 
Initially, the results for five of these mixtures were disappointing, but
in four of these five cases incorrectly certified SRM's caused the
inaccurate certifications.  Once the vendors had obtained the correct
certified value for their SRM's, their revised SO2 concentrations differed
by less than 1% from the EPA-determined value. All vendors supplied
complete documentation.

                                                % Difference   
            Nominal ppm    Date      Date    (Vendor-EPA) Complete
Vendor      NO    SO2    Certified  Checked  NO     SO2     Doc.  Notes

AGA-OH      400    300     11-93    12-93     1.5  -1.7     Yes
            900   1500     11-93    12-93     2.0   0.7     Yes

AIG-NJ      400    300      9-93    11-93     1.6   0.3     Yes
            900   1500      9-93    11-93     0.5   2.4     Yes      a

ASG-CA      400    300      9-93    11-93     3.2  -2.7     Yes
            900   1500      9-93    11-93    -0.6   1.4     Yes      b

LCC-PA      400    300      8-93    11-93     0.5   2.5     Yes
            900   1500      8-93    11-93    -0.1  -0.5     Yes      c

MGP-OH      400    300     10-93    12-93    -1.7   1.7     Yes
            900   1500     10-93    12-93     0.4  -1.4     Yes

MGI-PA      400    300      9-93    11-93     0.5  -0.6     Yes
            900   1500     10-93    11-93     0.7  -0.8     Yes

NSG-NC      400    300      9-93    11-93     0.0  -4.3     Yes
            900   1500      9-93    11-93     0.3  -1.9     Yes      d

SMG-CA      400    300     11-93    12-93     1.5  -1.4     Yes
            900   1500     11-93    12-93     0.6  -0.7     Yes

SSG-NC      400    300      9-93    11-93    -1.2  -3.2     Yes
            900   1500      9-93    11-93    -0.1  -0.7     Yes      e

a. Manufacturer used corrected value for NIST SRM, and reported (1-94) a
   new value of 1468 ppm SO2 (0.1% difference).
b. Manufacturer reported a new NO value (4-94) of 401 ppm NO (-2.4%
   difference), and no change for the SO2 value.
c. Manufacturer used corrected value for NIST SRM, reanalyzed the gas and   
   reported (2-94) a new value of 311.4 ppm SO2 (-1.3% difference).  
d. Manufacturer purchased new analyzer and reanalyzed cylinder, reported a
   new value (5-94) 302 ppm SO2 (0.7% difference).
e. Manufacturer used corrected value for NIST SRM, reanalyzed the gas and
   reported (1-94) a new value of 302.9 ppm SO2 (-1.7% difference).

                TABLE V.  Mixture NO/CO2 Protocol Gas Results

                                                % Difference   
            Nominal ppm    Date      Date    (Vendor-EPA) Complete
Vendor      NO    CO2    Certified  Checked  NO     CO2     Doc.  Notes

AIG-NJ      910   18%    7-93       5-94     -2.9   ---     Yes      a
AIG-NJ      540   18%    8-93       5-94     -2.2   ---     Yes      b

MGI-PA      880   18%    ? ?        5-94      1.4   ---     No       c
MGI-PA      900   18%    ? ?        5-94      1.8   ---     No       d

a. Client owned cylinder, has not been returned to vendor for 
   recertification. CO2 concentration well within 2%; exact value not
   determined.
b. Client owned cylinder, has not been returned to vendor for
   recertification. CO2 concentration well within 2%; exact value not
   determined.
c. CO2 concentration well within 2%; exact value not determined.
d. CO2 concentration well within 2%; exact value not determined.

             TABLE VI.  Mixture NO/SO2/CO2 Protocol Gas Results

                                             % Difference
            Nominal ppm    Date   Date    (Vendor-EPA)   Comp.
Vendor      NO   SO2  CO2  Cert. Checked  NO   SO2   CO2  Doc.   Notes

APC-IL      550  500  18%  4-94   5-94   -0.9  -0.2  ---   Yes     a

SSG-PA      570  530  18%  4-94   5-94    0.4  -0.2  ---   Yes     b

a. CO2 concentration well within 2%; exact value not determined.            
b. CO2 concentration well within 2%; exact value not determined.