This article is from the Food Preserving FAQ, by Eric Decker firstname.lastname@example.org with numerous contributions by others.
from an unknown poster, the chile-heads mailing list...
Keeping outside fermenting items a secret from the neighbors
I learned to love and make kim chee while attending college in Hawaii.
I encountered the same odor problem and was forced to come up with a
solution or get into a shooting war with the neighbors. Obviously, tightly
closing the fermentation container is a recipe for disaster. I actually
just cover my crocks with an unbleached muslin stretched over the top.
(Five gallon churns are the best "crocks" I have found.) However, I deal
with the odor problem by putting six inches of charcoal in the bottom of
a plastic trash can and setting the crocks on it. The charcoal I use is
provided by a friend at the Jack Daniels distillery, but any "raw" or
activated charcoal will work. Bagged charcoal briquettes, even when crushed,
are not really a good option, though. I use a large trash can and can
actually get three crocks in at once without crowding. I then put several
layers of burlap on top of the covered crocks. (I used laundered peanut
bags, but feed sacks would work as well.) Finally, I put the lid on the
trash can. The lids for these cans fit fairly tight, but will allow for
the equalization of pressure. You can still smell the kim chee working,
but you must get very close to the trash can and sniff hard.