Although I appreciate the Scuba Scuba Doo episode, but my vote goes for Conway the Contaminationist. That episode is more of a tribute to Dr. Thrax from the C&C Generals : Zero Hour game, the health of that episode seems true if you leave your room unclean until it may affect your health.
But in this case, like Dr. Thrax, you breathe in the polluted air and then you breathe out, so how does it feels. The doctor says good, but to us is very bad.
Overall, the 2 episode together I voted for is 7.5, it can't be necessary to be more than that.