Reference: Royal Society of Chemistry
Sulfur dioxide is a colorless gas with a suffocating, choking odor. It is toxic to humans and concentrations as low as 8 ppm will produce coughing. Incredibly, in the Odyssey, Homer describes the burning of sulfur (formation of SO2) as a way that homes were 'fumigated'.
Hydrogen is the most abundant element in the universe, making up about 75% of all normal matter by mass.
Prairie dogs, those little pups popping in and out of holes on vacant lots and rural rangeland, are talking up a storm. They have different "words" for tall human in yellow shirt, short human in green shirt, coyote, deer, red-tailed hawk and many other creatures.