

Keep in mind this is the absolute funniest he has ever been. A pun with a punchline and no setup.
The best he has ever done is get 50% of the way to a mildly funny joke. With his trademark inability to read the room on top !
(and don’t tell me that’s because he’s autistic. I’m autistic, we’re disadvantaged in this domain but we can learn to do it all the same. He either doesn’t know or doesn’t care, most likely the latter.)
It’s carbon dust, which your body is pretty good at dealing with, and in quantities so trivial you probably already inhale more currently than you would using a pencil in an otherwise mostly sterile spaceship (at least sterile compared to earth)