25 Pa. Code § 123.44
(a) A person may not permit the operation of a coke oven battery in a manner that visible fugitive air contaminants are emitted in excess of the emissions allowed by the following limitations:
(1) The following open charging limitation applies to existing batteries listed in § 121.1 (relating to definitions). The following closed charging limitation applies to any existing battery on which a closed charging system is installed:
(b) The following techniques shall be used for measuring and recording visible fugitive air contaminants from a coke oven battery:
(3) Observations of door area emissions for determining compliance with subsection (a)(3) shall be made from a minimum distance of 25 feet from each door. Each door area shall be observed in sequence for only that period necessary to determine whether or not, at the time, there are visible emissions from any point on the door area while the observer walks along the side of the battery. If the observer’s view of a door area is more than momentarily obstructed, for example, by door machinery, pushing machinery, coke guide, luter truck or opaque steam plumes, he shall record the door area obstructed and the nature of the obstruction and continue the observations with the next door area in sequence which is not obstructed. The observer shall continue this procedure along the entire length of the battery for both sides and shall record the battery identification, battery side and oven door identification number of each door area exhibiting visible emissions. Before completing the observation of door area emissions, the observer shall attempt to reobserve the obstructed doors. Compliance with subsection (a)(3) shall be calculated by application of the following formula, which excludes two door areas representing the last oven charged from the numerator and obstructed door areas from the denominator:

(4) Observations of visible emissions from a coke oven topside, other than emissions from the topside defined as open or closed charging emissions or pushing emissions, shall be made and recorded during the time an observer walks the topside of a battery from one end to the other, positioning himself near the center line. During the traverse, the observer may stray from near the center line of the battery and walk as close to the offtake piping as is necessary to determine whether an observed emission is emanating from the offtake piping. Each oven shall be observed in sequence. The observer shall record the battery identification, the points of topside emission from each oven, the oven number and whether an oven was dampered off. Compliance with subsection (a)(4) shall be determined by application of the following formula:

The provisions of this § 123.44 issued under section 1920-A of The Administrative Code of 1929 (71 P. S. § 510-20); and section 5 of the Air Pollution Control Act (35 P. S. § 4005).
The provisions of this § 123.44 adopted August 12, 1977, effective December 31, 1977, 7 Pa.B. 2251; corrected November 4, 1977, effective December 31, 1977, 7 Pa.B. 3260; amended August 12, 1983, effective August 13, 1983, 13 Pa.B. 2478; amended December 26, 1997, effective December 27, 1997, 27 Pa.B. 6804. Immediately preceding text appears at serial pages (215785) to (215788).
This section cited in 25 Pa. Code § 123.1 (relating to prohibition of certain fugitive emissions); and 25 Pa. Code § 129.16 (relating to door maintenance, adjustment and replacement practices).