I filled the vents in the Toxic Gas room with water (and had one left), and then there's this

I never thought of that! Great way to save a purity potion (very useful for on diet). Thank you OP

I don't get it. What's wrong? You missed one of the traps because it had gold on it?

Am I missing something?

I filled the vents in the Toxic Gas room with water, and they stopped spewing gas into the room. I left one vent as as proof of that.