The Environmental ProtectionAgency's Acid Rain Program, as defined under Title IV of the 1990 Clean Air ActAmendments, establishes a national cap on sulfur dioxide (SO2) emissions andtargets reductions in both SO2 and oxides of nitrogen (NOx) emissions. To establishcompliance, utilities and other industrial facilities must meet requirementsfor certification, daily calibration and ongoing quality assurance of used in the Acid Rain program.

If your facility is impactedby these regulations, you'll want to take a closer look at the EPA protocolgases you use to calibrate your CEMS. You could be risking non-compliance andthe expense of unnecessary RATA tests.

The EPA's 1997 protocolguidelines allow wide flexibility in how protocols are analyzed. For thisreason, all EPA protocol gases are not created or analyzed equally.

Many gas suppliers promise+/- 1% accuracy, but delivery on this promise depends on critical choices theymake during production.

Differences can be dividedinto three critical areas. Each can significantly impact the final accuracy ofthe EPA protocol gas you use to calibrate your CEMS.

Traceability: The EPA's protocol documents require that EPAprotocol gases be traceable to: Standard Reference Materials (SRMs) andNIST-Traceable Reference Materials (NTRMs) provided by the National Instituteof Standards and Technology (NIST); or Primary Reference Materials (PRMs)provided by the Netherlands Measurement Institute (NMi). Direct traceability tothese materials ensures accuracy. Use of Gas Manufacturer IntermediateStandards (MGIS) can result in an unacceptable accuracy of beyond +/- 2%. Checkyour Certificates of Accuracy to see to which reference materials yourprotocols are anchored.

Analyzer InterferenceResolution: To save time and money incalibration, auditing and cylinder handling without jeopardizing compliance,Acid Rain utilities often purchase multi-component EPA protocol gases. Theseare protocols with more than one pollutant component in a cylinder (e.g.,sulfur dioxide, nitric oxide and carbon dioxide in nitrogen). Use ofinstrumentation that is interference-free during analysis of multi-componentprotocols is superior to mathematical corrections. Check your Certificates ofAccuracy to see which method was used to prepare your multi-componentprotocols.

Choice of ProtocolProcedures - Dilution vs. Nondilution:The EPA specifies two different procedures for preparing protocol gases.Procedure G1 requires direct comparison with a reference standard (SRM, NTRM,PRM or GMIS) without the use of a dilution device. Procedure G2 allows gasmanufacturers to use dilution devices for comparison between the protocol gasbeing prepared and a reference standard. Diluting a standard (G2 analysis) addsuncertainty and is not as accurate as using a direct SRM, PRM or NTRM (G1analysis). Check your Certificates of Accuracy to see which procedure was usedto prepare your protocols.

The use of GMIS traceability,mathematical analyzer interference corrections and use of Procedure G2 caneasily degrade accuracy when preparing EPA protocol gases. When used incombination, they can yield a total error in excess of 3% or more, which leadsto regulatory non-compliance.

To avoid costly downtime,noncompliance fines, negative publicity and unnecessary RATA testing expenses,ask your supplier these important questions before you purchase another EPAprotocol gas for your environmental measures:

• What kind of reference standards do you typically analyze against? NTRMs, SRMs or PRMs to achieve direct NIST traceability, or against GMISs which may have too much uncertainty to create a truly accurate mixture?
• How does your laboratory resolve interference effects in multi-component protocols? (Ask your supplier to show you how multi-component analysis interferences are avoided.)
• Which "no interference" technology do you use when preparing multi-component protocol mixtures? (Ask your supplier to supply backup analytical data.)
• Which protocol procedure does your laboratory use to certify protocol gases? Procedure G1, without dilution is ideal. Procedure G2 should be used only when a NIST SRM, NTRM or PRM is not available.
• Do you participate in NIST NTRM programs? Suppliers who don't may not always be able to provide directly traceable EPA protocol gases.
• What is your lead time for manufacturing a protocol gas? Lead times longer than 12 to 18 calendar days may suggest inefficient production processes or inadequate reference standard inventories.
• What information do you provide on your Certificates of Accuracy and labels? (Examine examples of documentation and compare them with EPA requirements to ensure accuracy and completeness.)
• Do you provide other critical services that can help ensure regulatory compliance? Inventory management, on-site evaluations and needs assessment services can help eliminate all primary reasons why utilities fail environmental audits.

By applying these standardsin your selection of EPA protocol gases, you can maximize the efficiency andaccuracy of your CEMS and potentially push your performance far beyond the 10%requirement of the EPA's Acid Rain Program.

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