VEO Questions and Answers
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Corrective Lenses, Sunglasses and Opacity Readings
Method 9 establishes the requirements for certification to read opacity emissions.
It prescribes only one reason that causes a certification to no longer be valid in Section 3.1: "The certification shall be valid for a period of 6 months, at which time the qualification procedure must be repeated by any observer in order to retain certification."
Therefore, the certification is no longer valid if a candidate fails to certify at the end of the 6 month period from the previous certification.
This issue is legally undetermined, so the safest action would be to recertify, but it is not required by law. Common sense would say if an observer's eyesight has changed enough to merit a significant change in their corrective lense prescription during their six month certification period, they should re-certify before make further observations.
The following is what Method 9 states about corrective lenses. 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."