| Text of Test Method 9 - Visual Opacity |
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| Visible Emissions Field Manual |
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| Visible Emissions Evaluation Procedures Course |
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| Collaborative Study |
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| Optical Properties and Visual Effects of Smoke Stack Plumes |
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| Section 3.12 of the QA Handbook, Volume III |
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FREQUENTLY ASKED QUESTIONS (FAQS) for Method 9
When performing a Method 9 observation, what is the correct procedure if a 15–second reading is missed for any
reason (plume rolling, distraction, etc.)?
If for any reason a 15-second reading is not made, a dash should be placed on the data sheet (with an explanation provided in the comments section).
Running averages (e.g., 6-minute average) should not include a time lapse when a valid reading could have been made,
but should include those lapses where a reading could not be made for reasons beyond the observer's control (plume rolling,
fugitive emissions in the way, etc.). In calculating running averages, you would use 23 (or fewer readings
that cover that 6 minute period). For a more detailed description of the procedure, see Sections 6.1 and 4.3.2, I and J
of the QA Handbook here.
Still have questions on this method? Contact the EMC
expert Jason DeWees at
dewees.jason@epa.gov .
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