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Method 3A - CO2, O2 - Instrumental

Text of Test Method 3A - CO2, O2 - Instrumental PDF file
Evaluation of EPA Methods 3A, 6C, 7E Word Perfect file
Alternative for Methods 3A and 6C (ALT-004) PDF file



FREQUENTLY ASKED QUESTIONS (FAQS) for Method 3A



Do I really have to calibrate my Methods 3A and 6C instruments with upper level calibration gases between every test run? That uses up a lot of expensive calibration gas and cuts into my profit?

You could save on the cost of some of the Protocol 1 calibration gases and the shipping of same by following Test Method 205 (linked here). This helpful procedure describes the use of calibration gas dilution devices to produce numerous calibration gases for just such instrument checks without lugging all those cylinders to the test site.

Historically, ambient air or hydrocarbon-free air cylinders have been used as high-level calibration gas for Method 3A oxygen monitors. The update specifies Protocol 1 gases for all calibrations. This will be more costly than the older method. Are there any provisions for using ambient air or hydrocarbon-free air for O2 calibration gases?

Purified ambient air is still allowed for Method 3A. Mention of it was an inadvertent omission in the final revisions. This provision will be added back in the correction notice. The purified air should be free of any interfering components.

Is Equation 7E-9 correct? It seems to give unusual results.

Equation 7E-9 in the final rule appears to be correct; at least, it's essentially the same equation taken from old Method 20.


Do you have questions about a Test Method, Performance Specification or Source Category? Find the EMC contact for your question by clicking on the "EMC Contacts" link at the menu on the left of your screen, or use the direct link here.

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