(Adopted 7/2/68, Revised and Renumbered 10/22/68, Revised 5/23/72, 2/20/79)

A person shall not discharge into the atmosphere from any single source of emission whatsoever any air contaminants for a period or periods aggregating more than three (3) minutes in any one (1) hour which are:

  1. As dark or darker in shade as that designated as No. 1 on the Ringelmann Chart, as published by the United States Bureau of Mines, or, (Rev. 4/1/73)
  2. Of such opacity as to obscure an observer's view to a degree equal to or greater than does smoke described in subsection (A) of this Rule. (Rev. 5/2/74)

Note 1. Water mist alone is not a "noxious mist" and therefore is not an "air contaminant".
Note 2. The Air Pollution Control District will, from time to time, prepare and distribute statements of practice for administering Rule 50. Such statements are not adopted by the Air Pollution Control Board as part of this Rule. They are guides to staff activity and are intended to be helpful guides to the public.
Note 3. For the purpose of this Rule, "observer" is defined as either a person certified in reading smoke or a certified, calibrated monitoring system. (Added 2/20/79)

(Exceptions to this Rule as noted in Rules 55, 72.1, 72.2, 72.4, 72.6, 72.10, 73.1 and 74.1)