Mouseketeers et al:

Ferrets, diesel fuel, popcorn, poetry.  My, my, my.  All of
these seem symptomatic of bleeding threads (Animal drivers,
Diesel, Manifold Destiny, FFFRIDAY, etc.).

As for cats, BTST (been there, still there).  My cat
population is down from 15 to 5, but it's more a problem of
"so many mice, so little time."

I pulled off the front grills, see that there is a plastic
screen in front of the intake duct (maybe 1/2" gap around
it).  I suppose I could tape the gap (I know that 1/2" is
big enough for mice), but wouldn't they just chew through
the tape?

Again, my original question:

>>> Is there another way into the ventilation system  <<<
>>> other than the front grill that I can seal up?    <<<

Is there a connection to this system lower to the ground
(drain maybe?) where mice can get in?  Or do I *have* to
assume that the critters can *only* enter the system through
the front grill?

-Jim (not fond of emoticons,
      but "colon-dash-close-paren") Bryant