How dangerous is sulfur to humans?

Sulfur burns with a nice blue flame under normal atmospheric conditions, but in pure oxygen.The products of the fire are sulfur dioxide and sulfur trioxide.

quenching the burning sulfur with a small amount of distilled water can be used to demonstrate this.

In the following demonstration, a small amount of sulfur is heated in a Bunsen burner until it begins to burn, and then lowered into a jar of pure oxygen.After the sulfur flares up into a bright blue flame, it begins to release fumes of sulfur dioxide and trioxide.

Exposure to the fumes of sulfur dioxide and sulfur trioxide will cause them to hydrolyze to sulfurous and sulfuric acid.