Hydrogen sulfide is particularly dangerous because:

Hydrogen sulfide is particularly dangerous primarily due to its ability to cause immediate unconsciousness. This gas is not only toxic but also can be lethal even at relatively low concentrations. When inhaled, it can rapidly affect the nervous system, leading to a loss of consciousness in seconds to minutes depending on the concentration in the environment. This characteristic makes it exceptionally hazardous in situations where workers may encounter it without immediate warning, as they may not have time to evacuate or take protective measures.

Other aspects of hydrogen sulfide contribute to its risk, but they don't define its immediate danger as sharply. For instance, while it has a distinct rotten egg odor at low concentrations, this smell diminishes at higher concentrations due to olfactory fatigue, meaning that individuals may not realize they are still exposed to dangerous levels. Additionally, although hydrogen sulfide is corrosive, this property is more associated with its potential to damage materials and equipment rather than directly impacting human health in an acute manner. Lastly, while hydrogen sulfide is a concern in relation to long-term exposure and has some associations with cancer, it is not classified primarily as a carcinogen, making its acute impacts far more pressing in terms of immediate risk to life.