The eeriness of this line might have something to do with the fact that we don't know who the "someone" stumbling about in the night actually is.
Notice how the verbs here have changed: our speaker's no longer describing universal conditions that could apply to anyone.
He's in the moment, watching as a man is "stumbling" and "yelling" and "floundering."
Those "–ing" conjugations of verbs create a sense of immediacy.
The man's out there right now. His actions occur as we speak.
As we say in our "Quotes" section, lime, or quicklime, is a chemical compound that can burn through the human body (sort of like fire).
In other words, whatever the gas is doing to that man out there, it's awful.
It's so awful that our speaker can't face it head-on: he has to describe it through similes, (like those similes we talked about in the first lines).