Question

What is the smell of hydrogen sulphide?

Answer 1

Hydrogen sulfide may be a colorless, flammable, extremely hazardous gas with a “rotten egg” smell. Some common names for gas include gas, stink damp, swamp gas, and manure gas. It occurs naturally in crude petroleum, gas, and hot springs. In addition, sulfide is produced by bacterial breakdown of organic materials and human and animal wastes.

Complete answer:
Hydrogen sulfide is both an irritant and a chemical asphyxiant with effects on both oxygen utilization and therefore the central systema nervosum. Its health effects can vary counting on the extent and duration of exposure. Repeated exposure may result in health effects occurring at levels that were previously tolerated with no effect. Low concentrations irritate the eyes, nose, throat, and systema respiratorium (e.g., burning/ tearing of eyes, cough, shortness of breath).
Asthmatics may experience breathing difficulties. The consequences are often delayed for several hours, or sometimes several days when working in low-level concentrations. Moderate concentrations can cause more severe eye and respiratory irritation (including coughing, difficulty breathing, accumulation of fluid within the lungs), headache, dizziness, nausea, vomiting, staggering, and excitability.
The primary route of exposure is inhalation and therefore the gas is rapidly absorbed by the lungs. Absorption through the skin is minimal. People can smell the “rotten egg” odor of sulfide at low concentrations in air. However, with continuous low-level exposure, or at high concentrations, an individual loses his/her ability to smell the gas albeit it's still present.

Note:
Hydrogen sulfide is heavier than air and should follow the bottom. It collects in low-lying and enclosed, poorly-ventilated areas like basements, manholes, sewer lines, underground telephone vaults, and manure pits.