"Smoke units" means the number obtained by multiplying the smoke density in Ringelmann numbers by the time of emission in minutes.
For the purpose of this section, Ringelmann density reading is made at least once every minute during the period of observation; each reading is then multiplied by the time in minutes during which it is observed; and the various products are added together to give the total number of smoke units observed during the total period under observation.
(Ord. 10-16-67. Passed 11-20-67.)