Is a dry bag odor-proof?

Another sack option is Nylofume bags. This is a dense type of plastic bag used by termite fumigation crews. Its intended purpose is to keep lethal chemical gas out of food, but by the same token it can keep food odor inside the bag.

Some termite companies sell these for $1 each in a size 20×40 inches.

–B.G.–

A great way to test different materials and get meaningful results would be to train a dog to sniff for food, then hide different bags around and have it take a look around. Basically the same way law-enforcement uses canines to search for narcotics.

To the OP: Bears have a sense of smell anywhere from several hundred to several thousand times more powerful than a human (I've also read 5x as sensitive as a blood hound's). I heard the following from an old timer in Montana several years ago, so take it with a grain of salt, although from my even relatively limited outdoors experience I can easily believe it:

A cabin was broken into by a bear, most likely a black bear, which consumed all but three unlabeled and unopened tin cans of food. When opened, each of the three cans contained sourkraut. Guess the bear disliked German cuisine! In all seriousness though, I severely doubt any dry bag is at all odor proof when it comes to a bear's nose.

I've been wondering this for a few days and along comes this thread. How about putting the food in a opsak; the opsak in a drybag and the drybag under water?
(weighted with a rock I suppose)

In a place like SEKI lakes are everywhere. I just can't see how this wouldn't work but certainly have NO experience (with Sierra bears anyway)

Anyone with experience in Scu BBuh ( self contained underwater Bear Bags)

Heard of that being done as well, only with black garbage bags. Well #1, the rangers don't want you doing it, at least in the High Peaks of the Dacks (I inquired after hearing the story as I thought it would solve the bear can problem). The other problem is that bears swim :( So really, the can is the best and only true defense against a hungry bear. Everything else is susceptible if the bear is hungry and creative enough (anyone who has camped in the Marcy Dam area of the ADK knows the elder female nicknamed Yellow Yellow!).