Hydrogen sulfide is a toxic gas that smells like ____. At high concentrations of hydrogen sulfide, however, the sense of smell is deadened and no odor is detected.

• A. Rotten eggs
• B. Dead fish
• C. Fuel gas
• D. Rotten cabbage

Answer: (D)

Hydrogen sulfide is known for its rotten eggs odor, which is produced by the sulfur-containing compounds it releases. At low to moderate levels, this smell acts as a warning sign, but as the concentration rises, the gas dulls and can deaden the sense of smell, meaning you may not detect it by odor alone. Because you can lose the ability to smell H2S even when people are still exposed to dangerous levels, rely on proper detection equipment and safety procedures rather than solely on odor. The best fit for the blank is rotten eggs.