(a) Owners or operators of any iron and/or steel process must not cause or allow emissions from that process to have an opacity, determined by the method of subdivision (b) of this section, which exceed the limits contained in Table 2 of this Part, unless exempted under section 216.10(b) or (c) of this Part.

(b) Compliance with the opacity standards will be determined by observing visible emissions discharged during the operation of the iron and/or steel process. The observer must stand at a distance sufficient to provide a clear view of the visible emissions with the sun oriented in the 140° sector of his back. The opacity of emissions will be computed by averaging the results of 24 consecutive opacity observations made at 15-second intervals. For cyclic processes that generate emissions for less than six minutes per cycle, observations will be made only during the operation of the process when visible emissions are generated. A sufficient number of process cycles must be observed to accumulate the required minimum of 24 consecutive opacity readings.

(c) The fugitive opacity limits in Table 2 of this Part are applicable to emissions emanating from building openings.