Hydrogen sulfide:

A flammable, colorless gaseous compound of hydrogen and sulfur (h2s) , which in small amounts has the odor of rotten eggs.

Sometimes found in petroleum, it causes the foul smell of petroleum fractions.

In dangerous concentrations, it is extremely corrosive and poisonous, causing damage to skin, eyes, breathing passages, and lungs and attacking and paralyzing the nervous system, particularly that part controlling the lungs and heart.

In large amounts, it deadens the sense of smell.

Also called hepatic gas of sulfureted hydrogen.