yes. hydrogen sulfide is a deadly poison even in small amounts and the more oxidized species are highly corrosive (acids). The good news is that they smell like heck even at very low concentrations so usually you back off from the source before it can do much damage.
-
Any gas inhaled in high quantities or concentrations is bad, even oxygen in high concentrations is not good for you. Anything other than oxygen and nitrogen is bad because our lungs aren't made for breathing them, this includes sulfur gases.
-
Yes, sulfuric gases are poisonous