What is name of gas that kills lichens and comes from factories?

The gas that is known to harm lichens and is emitted from factories is sulfur dioxide (SO2). This pollutant is a byproduct of burning fossil fuels and industrial processes. Sulfur dioxide can lead to acid rain, which negatively affects ecosystems, including the delicate balance of lichen populations. Lichens are particularly sensitive to air pollution, making them important indicators of environmental health.