The plasma wouldn't have instantly cooled off when the water hit it, so some structural damage should have still incurred; and the gas would still fill the area if left unmolested, so it's probable someone might breathe it prior to it being dealt with. Plus, unless someone had knowledge of that precise reaction, or tools to measure the relative toxicity of the air, they might not even realize that it's poisonous until they ingest it. That's my take.
If you wanted to direct the gas out through the makeshift vent, that'd be cash.