Is a dry bag odor-proof?

[Eric Fredricksen]

Wishful thinking, probably, but might a dry bag be odor-proof, for improved bear bagging?

(I don't really understand how most any old unpunctured ziplock bag isn't odor-proof, frankly.)

[Bob Gross]

Take a ziploc bag and inflate it with air until it is tight. Seal it. Leave it on a table and check on it periodically.

A few will hold the air. Some will slowly leak. Some will quickly leak. It seems like some of the air gets out through the plastic pores and some gets out past the seal. So, I think they are halfway good, but not perfect. Other types of bags seem much better.

–B.G.–

[Eric Fredricksen]

Hm. I guess the difference between an ALOKSAK and an OPSAK is that the former has an impermeable seal, but the latter is sealed in terms of pores on the sides… And ziplocks are permeable everywhere.

I suppose dry bags aren't impermeable at the seal.

[Travis Leanna]

Ziplocs are most definitely NOT odor proof. Whether its the pores or leaky bags or whatever, just stick any food in them and even you can smell it.

OPSAKs work really well, IMO. They could be more durable, but if you're careful you can get some long use out of them. Just check them for holes before each trip.

[Gary Dunckel]

Interesting that this question just came up. Today I'm testing one of Lawson's roll top cuben bags for leakage during prolonged total immersion. I put a cotton T-shirt in the bag, rolled the bag closed, and submerged it for an hour in a bucket of water. Results: with 3 rolls of the closure, the T-shirt was a bit damp. Not soaked, but damp. With 5 rolls, the T-shirt was totally dry. Pretty waterproof, if you do enough rolls.

OK, so they're waterproof, but what about food odors? When I first received my order from Lawson last spring, I had the same question as the OP. So I took the bag that I figured would get the least use, and I put an open can of cat food inside a quart sized freezer bag (to keep the cuben bag cleaner in the event that a critter totally had its way with the food). I tied it to a pole a good distance from the patio and let the locals have at it. After 3 nights, it was evident that critters of various sizes and inclinations had messed with my bag. It had been moved all around, flipped over, and it had 3-4 2 mm size bite holes in it. However, security of the bag itself, and the food inside, was never breached. So, it looks like cuben bags (roll top type) might be water proof, but they are NOT odor proof. But they're darned tough and hard for a rodent to chew through.

[Eric Fredricksen]

Thanks, Gary. That pretty much answers my question then. Ah well.

(How many rolls did you do on the cat food dry bag?)

[Bob Gross]

Was the cat food still good to eat after three days?

–B.G.–

[Travis Leanna]

Dehydrated cat food is my staple backpacking food. Lasts for months.

[Bob Gross]

Sure, it lasts for months, because you can never force yourself to eat it!

–B.G.–

[j lan]

Aloksaks are not odor proof. opsacks are supposedly.

[Gary Dunckel]

Eric, I did the usual 3 rolls of the roll top. By the way, I did not close up the zip lock bag, as I wanted the odors to freely escape. I mainly wanted to try to keep the cat food off the cuben if I could (didn't work, as the raccoon–the likely culprit–really played soccer with the setup to try to get his dinner.

By the way, before I did my food test, I filled the bag with water and hung it for 3-4 hours. No dripping at all. Lawson makes great gear! I think that his bonding technique is the secret here. Stitched and taped bags probably would eventually leak, in time.

My next food odor test will be placing vacuum sealed goodies out. But not until I learn from the state wildlife folks what animal left me a scat souvenir a few days ago. It looks a lot like that of a garbage-fed black bear. If that's the case, I'll do no more testing at all.

[Bob Gross]

Get one of those trail cams set up. Then, when the raccoon or bear walks up, they will smile for the birdie.

By the way, in some states, if you get caught intentionally feeding wildlife, you can be cited.

–B.G.–

[Keith Selbo]

I don't know of any plastic that isn't gas permeable to some extent and it doesn't take much to alert a bear-sized olfactory organ. You need a metalized film bag to prevent oxygen from getting in and odors from escaping (available at some survivalist websites) and that's not the end of your problems. It's difficult to get the food in without imparting a tiny fraction to the outside of the bag. I suppose you could carefully wash the outside of the bag with a water soluble solvent followed by a water rinse. Seems like a lot of trouble though.

[Joseph Reeves]

I was asked to test drive the OPSAKS a few years ago after they had been reworked to make them more durable. They are certainly waterproof when closed correctly, and I believe them to be odor proof as well. We used them to store smoked salmon and a soup mix I make that easily permeates any zip-lock bag I’ve every used. One test was an always hungry Cairn Terrier up against the smoked salmon, which is her favorite, and which she considers to be her birthright. She never gave it a glance when it was covered with a light piece of cloth. When I followed up with the person who sent me the OPSAKS, she said that they did have bit of a dilemma about marketing the odor proof qualities of the OPSAK because of the inability of dogs to smell what was inside them. Let your imagination wander on that for a while.

We use them here without an Ursack after the bears have settled in for the winter just to cut down on weight. Never have had a problem with marmots, birds or squirrels.

But the original question here was regarding dry bags. They are not odor proof, but do offer some protection when using the OPSAK.

[Dan @ Durston Gear]

"it looks like cuben bags (roll top type) might be water proof, but they are NOT odor proof. But they're darned tough and hard for a rodent to chew through."

FWIW, I had an alpine rodent of some sort (packrat? marmot? pika?) put a dollar coin sized hole in my 1.5oz cuben Zpacks blast food bag last week.

[Steven Adeff]

big fan, I use them to store food, toiletries, food trash, etc. I use one as my dog's food bag. definitely odor proof to him, and definitely water tight. I believe they advertise watertight up to 60m? I know you can dunk it in water without worries when sealed properly.

[Jeff K]

Are there any smaller versions of the Opsak? I would like to keep my first aid kid in one as it does contain some things that are scented, but it appears the smallest one they make is 9×10.

[Gary Dunckel]

Jeff, BPL sells 3 smaller sizes than the 9" x 10". Check the gear shop, go to the available stock link.

[Jeff K]

Thanks Gary.

I see that they see some Loksaks in 4×7 and 5×4 dimensions. However, these aren't odor proof correct?

[Gary Dunckel]

"However, these aren't odor proof correct?"

They should be somewhat odor proof (better than a ZipLok), but they're not OPSaks.

[Jeff K]

Thanks. Odor resistant is good enough for me. That is until a bear spoons with me under my tarp trying to eat my Leukotape.

[David Heath]

I was wondering whether a bear could smell through food cans (tuna ,soup etc ) My research online says that they and probably other animals can detect food inside any container . If they can smell food in a hermeticaly sealed metal can they can certainly smell food in an opsack or other supposedly odor proof sack. Hence the need for a bear proof canister. The critters know there is food inside but cant get it out eventually they move on.

[Bob Gross]

A hermetically sealed food can has no odor coming through the metal can. However, there can be food odor on the outside, in the label, etc.

Bears don't always smell the food odor around the can, but they can sure recognize the shape of a food can, or the weight of a food can. They don't always know what is in it, but they know that it is their sworn duty to investigate it. That means they will test it with teeth or claws.

–B.G.–

[David Heath]

Along the lines of a home made food canister, an unlined 1.5 or 2 gal paint would work for some animals (mainly small) . Although not as tight as a factory sealed can, a paint can has a very tight lid that can be submerged. Its large size would be unfamiliar to a bear (assuming they recognize promising cans by their size) In actual field use however the can would have food smells on it and would probably attract a bear anyway. Still, a 1.5 gal paint can weighs less than a pound and might work in some situations.

[Kyle Meyer]

I use the hell out of the largest Opsaks, and they non-scientifically seem to work really well for keeping the odors in. I used them with great success hanging food in Olympic National Park when the bear wire was full, and we met 13 bears in three days on that trip.

One trick I use to figure out if it's still in usable shape is to pack my food prior to the trip and suck all of the air out of it as I seal it. If the bag has re-inflated after an hour, which has happened to one of them after about 25 nights of use, it's time to get thrown away or be repurposed.

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