When Hydrogen Sulfide H2S is present in the air in low concentrations, you can smell it, and yes, it smells like rotten eggs.
But, if Hydrogen Sulfide is present in the air in high concentrations, you can not smell it anymore. That is when it is deadly, and many people died by inhaling the gas when it leaks from chemical factories. It has no smell highly concentrated, and it is heavier than air, staying closer to the ground, where we humans walk.
Once person losses consciousness, and falls down, he usually falls in the place with even higher concentration of Hydrogen Sulfide.
I used to live in a city close to a chemical factory, and at one occasion, the whole city had to be evacuated, as the wind was blowing Hydrogen Sulfide leaking from the factory.
That day several people working in the factory died.