Volcano in Chile erupts for a second time | The New Daily
The link contains some pretty spectacular photos. May be a good idea to skip the visit there for a while.
Besides being a spectacular firework, it does put out a good bit of ash and gases. My guess it just wiped out a few years of clean air efforts.
Volcanic gas composition per USGS:
Volcanic Gases and Their Effects
The most abundant gas typically released into the atmosphere from volcanic systems is water vapor (H2O), followed by carbon dioxide (CO2) and sulfur dioxide (SO2). Volcanoes also release smaller amounts of others gases, including hydrogen sulfide (H2S), hydrogen (H2), carbon monoxide (CO), hydrogen chloride (HCL), hydrogen fluoride (HF), and helium (He).
And for what is volcanic ash Geology describes it.
Volcanic Ash and Volcanic Dust | Photos, Satellite Images, More