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Arrive Prepared

  • Bring a clipboard and pencil. We often have extras, but we can run out depending on the class size.  

  • Arrive early to find a viewing spot in time for the test runs.

  • Dress for the weather - you will be stationary for over an hour, maybe several. Dress to stay comfortable.

  • The field exam may be delayed, postponed, or rescheduled if winds are over 25 mph, though usually we can find a spot out of the wind behind a building.

  • Three-part carbonless forms will be provided. Write neatly and do not erase. You may cross out and re-write. The field exam form includes a diagram where you must include wind direction, sun position, distance to the smoke stack and north arrow in order to pass. A correctly filled out form demonstrates observer understanding of basic Method 9 requirements. Incomplete forms will result in failure.

  • Test runs for opacity observers to initially calibrate their eye to opacity levels will be conducted prior to the field exam.

  • A field exam consists of 25 black and 25 white readings.

  • To pass, an observer must correctly indicate each of the 25 readings within 15 percent for each smoke color, with a total deviation for each color of less than 190 and an average deviation of all 50 readings of less than 7.5 percent.

  • Observers must pass consecutive black and white runs to be certified.

  • An observer can repeat a field exam either onsite the day of the exam (by notifying the instructor of a failed test), or at another field location for the cost difference. Field exams will end when all readers leave the site.

About wearing sunglasses or transition lenses, please see EPA's Guidance below:

EPA-600/4-77-027b Feb. 1984 Section 3.12 Method 9 - Visible Determination of the Opacity of Emissions from Stationary Sources, Page 5, 4.3.1 Opacity Observations 7:


"It is recommended the observer wear the same corrective lenses that were worn for certification. If sunglasses were not worn during certification, the observer should remove them and allow time for the eyes to adjust to the daylight before making VE determinations. It is recommended that the observer not wear photo compensating sunglasses."

90 degree elbow assists opacity reading in the wind

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