ventilator

noun4

1. •
   A device that circulates fresh air and expels stale or noxious air.
2. •
   A machine that moves breathable air into and out of the lungs of a patient who is unable to breathe sufficiently.
3. •
   (figurative) Some behaviour or happening that relieves a tense atmosphere or situation.
4. •
   (slang, no longer used) A play or an actor so bad as to empty the theater.