I'd heard that the buffered eyewash agents had fallen into disfavor, as they are hard to keep clean and fresh until they're needed. And when they're needed, they're really needed. Generally, the whole purpose of the buffer is to treat your eyes gently and neutralize anything they come in contact with, while at the same time, flushing a contaminant away. You see? Any possible reaction should be happening for an instant in your eyes, and then be flushed away, to happen for a few more instances in the sink, then down the drain. I don't know the composition of every buffered eyewash, you will have to call the respective manufacturer and ask them specifically. As for gaseous H2S, in the lab, wafting out of the hood to react with a plastic sealed bottle of buffered eyewash and causing future blinding, well, there's a few layers of Whiskey Tango Foxtrot there, but you should probably not worry about that.