I am aware of the toxicity of H2S, I have, however, worked with it before.
If I recall correctly, it has a similar degree of toxicity with HCN, and the problem is, low concentrations make themselves known by the eggy stench, but quickly overwhelm the sense of smell, leading the not-so-careful or inexperienced experimenter to believe that the H2S has gone away.
I will of course make sure that I have a brand new canister on my gas mask, to protect against H2S, phosphine and diphosphine, I am not so worried about the higher phosphorus hydrides, although probably highly toxic they are both brightly colored, and solid.
I think, if working with phosphine, H2S is the least of one's worries, as I will certainly be taking the utmost care, using a scrubbing system to bubble the residual PH3 and H2S through absorbent chemicals and eliminate entirely, any possibility of venting into the atmosphere.