71. For the purposes of sections 68 to 70, the concentration of the contaminants emitted is determined using average concentration measured in the emissions over a period of 3 hours, expressed on a dry basis corrected to 15% oxygen according to the following formula:
E = Ea x 5.9
________
20.9 - A
where
“E” is the corrected concentration;
“Ea” is the concentration on a dry basis, uncorrected; and
“A” is the percentage of oxygen on a dry basis in the combustion gases at the sampling site.