Which gas is associated with a rotten egg odor and tends to accumulate in low-lying areas due to being heavier than air?

Which gas is associated with a rotten egg odor and tends to accumulate in low-lying areas due to being heavier than air?

• A. H2S
• B. SO2
• C. HCl
• D. CO2

Answer: (A)

Hydrogen sulfide is the gas that produces the rotten-egg smell, and it’s notably heavier than air, so it tends to collect in low-lying areas and confined spaces. This combination—rotten-egg odor plus density causing pooling in depressions—makes it the best answer. It’s also a highly toxic gas, which is why detection and ventilation are critical in any environment where it could accumulate. Other gases might have sulfur-related odors or be heavier than air, but they don’t match the distinctive rotten-egg smell and the same pooling behavior as hydrogen sulfide. CO2, for example, is heavier than air but odorless, and HCl has a sharp, irritating odor rather than rotten eggs.

Hydrogen sulfide is the gas that produces the rotten-egg smell, and it’s notably heavier than air, so it tends to collect in low-lying areas and confined spaces. This combination—rotten-egg odor plus density causing pooling in depressions—makes it the best answer. It’s also a highly toxic gas, which is why detection and ventilation are critical in any environment where it could accumulate. Other gases might have sulfur-related odors or be heavier than air, but they don’t match the distinctive rotten-egg smell and the same pooling behavior as hydrogen sulfide. CO2, for example, is heavier than air but odorless, and HCl has a sharp, irritating odor rather than rotten eggs.