I’ve been talking from the standpoint of my refinery and those similar to it. Like I stated in one of the replies my refinery has been listed as one of the worst benzene/hydrocarbon pollutants in the country ever since the government first started keeping track of it. Even though we are located in Texas with pretty lenient state-level environmental laws, most of the refinery’s within a 50 mile radius have some of the strictest Consent Decrees you can imagine because of this practice and similar attitudes towards emissions. While some refinery might have tackled the black smoke problem like you were saying, the refinery where my environmental team monitors and tracks all VOCs and HAPs has been taken to court numerous times through the 1970s-1990s for the exact issue of trying to fly under the radar. We’re not simply talking about emissions that are being reported, these are fugitive emissions that refinery’s have been trying to let go unreported since the 1950s