Environmental Protection Agency (EPA)  [ Return to  FAQ  ]

1. What are the Federal Guidelines for the preparation and analysis of EPA Protocol gas mixtures?
Current guidelines are contained in EPA-600/R-97/121; “EPA Traceability Protocol for Assay and Certification of Gaseous Calibration Standards” published in September, 1997.

2. How were these guidelines developed? 
The original guidelines were first issued in 1987 and published in the Federal Register in 1993. Also, in 1993 the original guidelines were revised by the EPA in conjunction with the various gas producers. In 1997 the present guidelines were modified to allow EPA Protocol gases to also be used by the EPA Acid Rain Division. Air Liquide again participated actively in the development of these new guidelines.

3. What happened to the two types of EPA Protocols?
In 1993 EPA Protocol 1 and EPA Protocol 2 were consolidated into a single group for all measurement applications. Previously Protocol 1 gases were used for continuous emission monitoring and Protocol 2 gases were used for ambient air monitoring.

4. What are the Federal Regulations, which require monitoring of continuous emission sources and ambient air quality? 
The Federal regulations are published in section 40 of the US Code of Federal Regulations parts 50, 58, 60, and 75.

5. What is the analytical accuracy to which EPA Protocols are manufactured and guaranteed?

Most EPA Protocols are manufactured and analyzed to an accuracy of <± 2%, called “EPA CEM GRADE” For many of the non-reactive minor component gas mixtures, our labs can often produce Protocols with <±1-% accuracy. We offer these mixtures as “EPA PRIMARY GRADE”. For certain reactive gases the accuracy may exceed ±2% particularly for lower concentrations, (Typically < 5 ppm). Note: Protocols with multiple minor components are available. Please contact either lab for more information on these mixtures.

6. What governs the range at which EPA Protocols can be made? 
The EPA guidelines specify that primary reference standards traceable to NIST standards must be used for comparison in all analyses. These standards include SRMs, PRMs (from the Netherlands), NTRMs, as well as Gas Manufacturer’s Intermediate Standards (GMIS) compared directly to one of the other standards listed. The 95% confidence level of the Protocol being analyzed must fall within ±1% of the reference standard concentration.

7. Why does it take so long for some EPA Protocol mixtures to be prepared?
Statistical techniques are employed to determine the stability of Protocols. For mixtures with reactive minor components including hydrogen sulfide, nitric oxide, oxides of nitrogen, sulfur dioxide and carbon monoxide, the stability of the mixture must be confirmed. After the first assay is made, the mixture must sit for seven days before a second assay is performed. If the 95% confidence levels of the two assays do not overlap, the mixture must sit an additional seven days before a third assay can be run. The 95% confidence limits for two of the three assays must overlap or the sample is rejected.

8. Can a Protocol, where the certification period has expired, be recertified?
Yes, the lab preparing the original mixture can recertify the Protocol. The residual pressure must be greater than 500 psig.