*BURBLE*
Lucian heard the distant sound of some kind of liquid flowing; it was quite low and hard to hear, but it was definitely there, and it was coming from the pipe.
Standing close to it, he listened to the sound carefully. Within a few seconds, the sound got a little louder and seemed to be getting closer.
Just as the sound got close enough, a strong scent of the liquid came out of the pipe.
Lucian inhaled it unconsciously, and all his sleep disappeared from his eyes as he smelled the scent that made him feel as if his windpipe had started to burn.
He jumped back immediately and covered his nose with a handkerchief, asking in his mind:
'What was that? That strong smell almost felt like... acid? But the scent was just too strong.'
[You are right on the mark.]