(a) Darkness of a visible emission of an air contaminant shall be graded by using the Ringelmann Chart or by means of a device or technique which results in measurements of equal or better accuracy.
(b) Opacity of a visible emission of an air contaminant shall be graded by observers trained by and certified by the Michigan Air Pollution Control Division, Department of Natural Resources using a device or technique approved by and on file with the Michigan Air Pollution Control Commission.
(Ord. 2494, passed 5-12-1975)