Read a bit further, the very next sentence???

> “All you could smell was sulfur hydrogen, and you cannot breathe,” Dr. Vrenozi said, recalling that most of the researchers were wearing masks. But as they descended deeper into the cave, she said that “you get used to the smell of spoiled eggs.”

Also, you use "" but you are not quoting, the text inside your quotes does not exist in the article. The actual quote would be

> The cave is hard to reach and is filled with foul-smelling hydrogen sulfide gas, in concentrations too great for most animals to live there.