Hydrogen sulfide is a toxic gas that is often emitted during fossil fuel extraction and transport, and some other industrial processes like the kraft process at paper and pulp mills. Are there emissions limits for hydrogen sulfide emissions?
In the United States, hydrogen sulfide is not considered a "criteria pollutant" or a hazardous air pollutant. Thus, there are no federal ambient air quality standards set for it. However, hydrogen sulfide emissions are somewhat regulated for major sources, in that industrial operations must apply for permits to emit more than 10 tons per year of hydrogen sulfide. States have a variety of regulations regarding hydrogen sulfide, including some states that do have ambient air quality standards for it. For more information, please see this wiki: https://publiclab.org/wiki/hydrogen-sulfide-regulations.