It’s the VENTILATION nozzle.
Money Heist Season 1, Episode 5
or, if it went wrong, two dead bodies
inside the VENTILATION ducts."
Money Heist Season 1, Episode 6
{\i1}The toilet's VENTILATION pipes{\i0}
Money Heist Season 3, Episode 6
even in the underground VENTILATION ducts.
Money Heist Season 1, Episode 11
They're putting tubes through
the VENTILATION pipes.
Money Heist Season 3, Episode 6