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How Safe Is Your Food? Investigating the effectiveness of odor-proof bags
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scent on 04/10/2013 21:54:00 MDT Print View


But, it doesnt prove or disprove any advantage of odor resistant bags in real situations.

As others said, what is wanted is to reduce the chance of a bear smelling your food 100 yds away, not 5 ft from it.

What you proved, was that there was enough odor from all the bags for the dogs to detect it within the small distance used.

I dont understand odors totally, but I do know this, you dont have to touch something, to leave an odor on it. Odors actually "fall" off objects, this is why a person leaves a scent trail, the person didnt touch the ground, just the bottom of their shoe, but their scent is there.

Following this reasoning, the bags could have easily been contaminated during loading, you just have no way to tell. Just because you didnt touch it, doesnt mean you didnt leave scent on the outside of it at all.

Edited by livingontheroad on 04/10/2013 21:56:05 MDT.

Sam Farrington
(scfhome) - M

Locale: Chocorua NH, USA
odor proof bag tests on 04/10/2013 22:39:58 MDT Print View

A couple years ago, I posted on GEAR a comparison test of Opsac and Ziploc bags in real woodlands with real wild critters, over several weeks time. The difference was stark.

The results were confirmed by use of Opsacs for unmolested trekking caches, and info about that was later posted also.

So now we have this article that purports to have some modicum of scientific reliability, and finds there is little difference. As Joe Biden said, "Malarky."

These were trained, domesticated dogs, not real wild critters.
Heaven knows what kinds of odor training they had already been exposed to.
Who knows what kinds of food might have been stored by students previously in the lockers.
The dogs were not given an opportunity go after the 'protected' food to see what else might have attracted them.
As already noted, no empty bags were used as controls.

Something done in the outdoors away from civilization, in areas populated by bears and other wild animals, for subsantial periods of time, and with the animals having an opportunity to get into the 'protected' food, would be useful.

Long story short, a good test for our purposes would simulate real life conditions and events as much as possible.

What really got me is that my scientific training is nil, yet despite the expressed reservations of a few, there is the oohing and aahing from members, many of whom have plenty of scientific training and should know better. (No names, you know who you are.) It raises the cosmic question: Can you rely on a dam* thing you read on the internet.

Good. Now I feel much better. Don't respond with angry posts, as I'll waste no more time on this thread; but should you really want to unload on me, feel free to PM, and I promise to read, maybe even respond after I cool off. Good hiking to you.

Edited by scfhome on 04/10/2013 22:50:43 MDT.

steven franchuk
Re: scent on 04/10/2013 23:05:59 MDT Print View


But, it doesnt prove or disprove any advantage of odor resistant bags in real situations.

As others said, what is wanted is to reduce the chance of a bear smelling your food 100 yds away, not 5 ft from it.

What you proved, was that there was enough odor from all the bags for the dogs to detect it within the small distance used."

Keep in mind that a bear doesn't need to use his sense of smell to find your camp. Many people follow established trials and campsites. Over time the bears will learn where those sites are. If they learn that people carry food then they will frequently visit esablished camp sites in the hope of finding food.

Once a bear is in your campsite the odds of him finding your food go up simply because he is closer to it. Furthermore the more you handle your food the greater the chance you will move the smell from inside the OP sack to the outside of your bear canister. Even if OP sacks attenuate the smell it won't help if the bear is in your campsite and the outside of the canister smells like food.

Even if you avoid heavily used campsites and somehow found a way to keep the smells in the OP bag bears can still find your campsite. How? They followed your smell. Bears know what humans smell like and none of us are taking any steps to eliminate our own smells.

So overall no mater how effective or ineffective OP sacks are bears will still be able to find your food. So if there is no way for you to prevent bears from finding your food, the only option left is to make it impossible for bears to eat it. And the only way we have of doing that now is toe use a bear resistant canisters.

so in my opinion the central conclusion of this study:

"The bags tested in this study are not 100% odor-proof as advertised and should not be relied upon as a stand-alone food protective strategy when travelling in bear country."

Is valid.

Dale Wambaugh
(dwambaugh) - MLife

Locale: Pacific Northwest
Re: Re: scent on 04/11/2013 00:02:58 MDT Print View

I've assumed that doubled freezer bags would help to slow down the discovery of my food. There are so many other factors in the field, with handling and associated odors leading my list. Animals learn to associate humans with food and we are walking odor factories, with soaps, deodorants, smelly feet, plastics, leather and a thousand other things we might have with us.

Bob's moth ball story is interesting. I have wondered why a repellent hasn't been developed, but it would probably be nasty for humans if it would deter a hungry bear.

The electric fence idea makes a lot of sense to me as it adds negative reinforcement to the mix. I think an electric version of an Ursack would be great and adding some electric charge to a bear can would add to creating negative associations with food and people. I would love to watch a raccoon grab an electrified food sack. It begs to have an indicator LED and remote control. A wire mesh electric bag for a backpack could be handy too.

Rob Lee
(roblee) - MLife

Locale: Southern High Plains
Re: Re: Re: scent on 04/11/2013 02:37:36 MDT Print View

Ari developed an interesting question, designed a simple pilot study to test under controlled conditions, all within constraints of time, money, and availability of subjects, handlers, researchers,and facilities. The results are simply presented to the intended audience with scientific vigor, and the experiment could be easily repeated to test its validity. Oh, and he did it on his own dime and the officers (both canine and human) received some free training. A few assumptions by me, but likely a high probability it was close to this scenario. His conclusion was not overreaching: "The bags tested in this study are not 100% odor-proof as advertised and should not be relied upon as a stand-alone food protective strategy when travelling in bear country."
Very practical study and practical/useful advice. Surf and Dale provided a good start on several variables that can lead Smokey to your stash well before he smells it. I'd add an additional small list: hearing you, seeing you, seeing your camp, his hunger level, good health status allowing him to forage far and wide and fast, breeding status, his level of aggressiveness,presence of cohorts that might exacerbate the situation, and how importance that particular spot of his territory is to him. A tip of the Sunday Morning Hat to you sir! And to those who responded with a sense of gratitude for the service you provided us and to those for whom this piqued a spark of wonder and curiosity. I'm looking forward to the foil bag test and any other of the fine challenges that a well crafted study always generates.

James Marco
(jamesdmarco) - MLife

Locale: Finger Lakes
Re: Re: Re: scent on 04/11/2013 04:19:26 MDT Print View

I think that our good experimenter made the articles point. That is, OP sacks don't work as a primary defense for food. Reason dictates that you should NOT sleep with them, ever. Secondarily, was that dogs, could smell scents through them, though dogs were only a means, not the actual target of the study. Like heating a flask in lab, using a bunsen burner was not the point of the experiment, though it also proved the burner worked.

Scent, like vision to you and I, appears to be a primary input to bears, dogs and cats. I suspect this also means there is specific qualities that we cannot detect. Like the amount of food available, overall shape of the scent source, direction, and other things we are unaware of. We can debate this to some degree. Dealing with our lack of fundamental knowledge in this area is perhaps another science in it's own right, and, while mentionable here, should not be debated, here, though.

Since the real life target was bears, I would quibble that the experiment should have used bears for better relavency, but, dogs work as well given the testing parameters: easily mobilized, easy to handle, not dangerous and usable within the constrained budget & time. No doubt, there would be quibles about individual animals if it had been done with bears: caged/wild/jaded/etc. Generally, a well done experiment with provable goals. Personally, I tentativle accept the results with the caveate that repeated testing would include a blind target, ie, one with nothing in it to remove all sources of possible contamination.

As far as techniques to maximize food safety and personal safety (albeit indirectly,) these debates do not effect the experimental results. We can debate the merits of various techniques freely. Ryan Jordan, et al wrote of electrical bear bags a few years ago, I think. Canisters are pretty well established, though often derided. I hate to carry the d@mn things, myself. Hangs and techniques are a normal part of camping. Electric fences are well known, but, usually avoided due to weight and complexity concerns. Metalic skinned films have been known for many years, since the latter 60's when they discovered dissappearing water in fallout shelters *through* plastics. I am sure there are others...

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: scent on 04/11/2013 09:14:19 MDT Print View

After the fact, you can always come up with differences in an experiment that might make it better. You have to decide on something, do the experiment, publish results, repeat if you want.

The fact that the dogs found some and didn't find others, with about the same number for regular bags and "odor proof" bags, puts a huge question mark on whether odor proof bags are effective.

And the fact that no experiments were found that showed effectiveness.

Ron Bell
(mountainlaureldesigns) - F - M

Locale: USA
OP Saks Work OK in the Field on 04/11/2013 09:38:04 MDT Print View

While many things in the article are inferred - but not proven - from this one non outdoor test as it relates to backpacking in the field - remember that there there exits a fairly large body of practical user experience and reports OP Saks working very well in the field in backpacking settings.

I find this broad and direct backpacking user information a FAR more compelling a reason to continue to use them as one important part of a safe food carry and protection system. I know I feel safer with my food in an OP Sak and then rolled inside a thick cuben dry bag vs anything else short of a full bear canister, and like most all lightweight backpackers I'm not planning to carry one of those except where required or in special cases.

Disclosure - we do sell OP saks at MLD, but it is a fairly low profit item - in fact we hardly make any money on them as many orders are for only one set of the bags- not much profit after all the order processing and shipping handling, stocking , etc for a fairly low cost item.

The following quote is from Ryan Jordan, backpacking light owner from the BPL product page from when they were sold in the BPL Store a few years ago.


" Are O.P. Saks Really Odor-proof?
Well, yes, quite so. We slathered a bunch of honey, peanut butter, and olive oil in one and left it out for four days in the corner of a forest service cabin while we were out tramping around on a hike. We knew the cabin to be infested with both mice and pack rats, and when we came back, the O.P. Sak was intact with no sign whatsoever of animal intrusion, despite the fact that there were fresh droppings and sawdust scattered throughout the cabin.

Ursack liners are actually O.P. Saks. And, we've been using O.P. Saks for food storage while backpacking in both grizzly and black bear country in Glacier NP, Yellowstone NP, the Bob Marshall Wilderness, Tetons, Wind Rivers, and Uintas. Below the treeline, we simply add a mesh sack with a drawcord and hang our food with AirCore Plus. Above the treeline, we store the O.P. Sak under a pile of rocks, or sometimes, just sleep with it next to our shelter. Even in the most rodent-and-bear-infested areas, we've not had a single curious critter attempt to get into the O.P. Sak. "

Edited by mountainlaureldesigns on 12/16/2013 16:16:23 MST.

Michael Tauben
(mtauben) - MLife

Locale: My heart is in the hills
No surprise on 04/11/2013 09:51:46 MDT Print View

These types of studies on subjects many people people would never even think about is why I have alway loved BPL.

Anyway this came as no surprise to me as I have been backpacking with dogs for years and have used OP sacks for both my own and my dogs food and believe me the dogs know exactly what is in the bags and know when meal or snack time has arrived. I still do use OP sacks, however, I have come up with a system where I put all food in ziplock bags first, so all food residue stays in there, and then put multiple zip bags in one OP sack. This does not really cut down on my dogs ability to smell the contents but means everything is more secure against moisture, bugs, rodents and other issues. It also extends the life of the OP bags so I can use them over and over again. I also always use the PCT hang method.

I think another interesting issue here, however, is the subject of keeping bears away altogether. We are in their territory when we are out in the wild and should never forget that. We either except the inherent difficulties of that or we don't. By the way, ironically enough, the most effective way at keeping bears away is to have a dog with you in the backcountry. You guys at BPL should ask Justine/Trauma, about his experiences with his dog Yoni. There is more than enough anecdotal evidence to support this idea, and could make a good study topic for BPL. But to me it is a fact and just another great reason that all land in this country should be opened up for responsible dog owners to enjoy with their best four legged friends.

Greg Mihalik
(greg23) - M

Locale: Colorado
Re: OP Saks Work OK in the Field on 04/11/2013 09:56:34 MDT Print View

"While many things may be correctly or incorrectly inferred - but not proven - from this test as it may apply in the field - there exits a fairly large body of practical user experience of with OP Saks in the field. "

Sort of like the anecdotal experiences and folk lore about water treatment and giradia.
Stories are nice, but I like science.

Mary D
(hikinggranny) - MLife
Similar test, opposite results! on 04/11/2013 10:02:15 MDT Print View

While this article is interesting, it completely contradicts the test I did several years ago with my own dog, as reported in detail on page 2 of this thread. (I'm surprised nobody has commented.) My dog easily smelled his kibble from several feet away through two layers of freezer bags and started to tear into them. With the food in an OP sack, he either walked by or took a quick sniff and walked away. That's quite a difference!

I never have and never will rely on OP sacks to be effective against bears (OK, that's the same conclusion as the article), but at least with the OP sacks, I could turn my back on my food without worrying about my dog's getting into it! My dog clearly demonstrated that OP sacks are definitely more odor-resistant than two layers of freezer bag.

Basically, the article only demonstrates that OP sacks will not keep specially trained dogs out of "controlled substances." How about testing with food? If you have a dog of a hunting breed (retriever or scent hound), freezer bags, an OP sack or two and some odoriferous dog kibble, try your own experiment!

As a dog owner, I would caution against relying 100% on the dog handlers' statements about their dogs' abilities. We all think our dogs are perfect--dogs do inspire that kind of love!

Edited by hikinggranny on 04/11/2013 10:09:29 MDT.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Similar test, opposite results! on 04/11/2013 10:22:50 MDT Print View

You could do an experiment with bears - leave out a number of OP sacks and regular bags, spread around in a wild bear area and see which ones get broken into - but then you would be teaching bears to eat human food so you would never do this.

I agree, controlled substance trained dogs is a difference from reality that makee the results questionable.

Richard Nisley
(richard295) - M

Locale: San Francisco Bay Area
Re: Similar test, opposite results! on 04/11/2013 10:31:24 MDT Print View

In 2006 I asked a dog trainer to test OP Saks for me and he came to a similar conclusion to Mary's. His forum post was as follows:

paul johnson
(pj - M) SUBJECT Re: OP Sac Test Request - Please ON 06/08/2006 00:27:20 MDT POST REPLY


I've tested it with my sole remaining dog. Well, actually, my wife's new puppy. Like all growing pups, he's a real "chow hound".

I've tried both cheese and peanut butter, and his favorite bacon scented chew (the bacon scent is so strong, i can smell it faintly just entering the kitchen.

First, the pup is placed upstairs out of "earshot". The pup, just 5mos old, already associates the sound of all types of noise related to plastic bags with food.

Then, a two person assembly job. I never touch the foodstuffs or chew. She doesn't contact the zips. My wife places each of them in a Glad zip-lock bag. Then, each of the two zips are placed in an O.P. Sak purchased on the BPL website some many months ago.

O.P. Saks are placed in dining room. Pup eventually finds them as he wanders about (plastic odor??? or serendipity???). The pup is curious, sniffs, and ignores the O.P. Saks.

Now the Glad zips are removed from the O.P. Saks and placed in a freezer sized zip-lock bags. The test is repeated. Bags are placed in dining room.
Pup finds the bags and bites at the bags.

Need to do the test in this order since a dog (and most animals), when it comes to food, can learn to associate (probably not a memory in the human sense of memories, hence the term association) from a single exposure/experience. That is, to be a little clearer, if the test is done the other way around, a dog, the pup in my case, would be attracted to the O.P. Sak simply because it had already learned or associated food with plastic bags.

Richard, i've had dogs for years and though an amateur have much experience training dogs - both mine and friends. I would also kennel friend's dogs at my home, where they all would receive some obedience training even if that wasn't the purpose for the stay.

Training for my dogs consisted of on and off lead obedience, out-of-sight whisper commands like used with sentry dogs in Viet Nam, protection, tracking, and now therapy-dog with my wife's new puppy which she's already using with her oncology patients to keep their spirits up while they are getting chemo.

In the field, co-worker didn't use O.P. sack. He hung his food. I didn't hang my food (no bears, but a lot of rodents). My food in plastic bags inside of O.P. Sacks - actually tripled bagged - yeah...i know...perhaps overkill. His tent, pack, and plastic storage bags were all bitten through by a bold nocturnal rodent raider to get to a candy bar - still in wrapper - that he forgot was inside of his pack. My gear and food untouched.

As far as i'm concerned O.P. Saks work.

Note: A friend of mine an ex-USAF and long-time professional dog trainer (IMHO, the best i've ever encountered) has many Shutzhund competition dogs and a large clientelle. He has stated that next to him, i was ("was", not "am" - it was about 20yrs ago he said this) the best dog trainer he knew in the State at that time - he was probably being kind and was exaggerating. I use something akin to the Koehler method which is staunchly based upon an understanding of canine psychology as the proper foundation and basis for all canine training. Just "Google" Bill Koehler is interested - amazing credentials. Most public libraries have one or more of his four books.
Edited by pj at 06/08/2006 01:12:30 MDT.

Ike Jutkowitz
(Ike) - M

Locale: Central Michigan
Time for diffusion on 04/11/2013 10:42:24 MDT Print View

Richard and Mary,
Thanks for the feedback. It was be interesting to see those tests repeated (ideally with more than an n of 1) , allowing 24 hours for the food to sit in contact with the bags.

Mary D
(hikinggranny) - MLife
Dog testers on 04/11/2013 12:08:55 MDT Print View

Does anyone have a pack of beagles or foxhounds or bloodhounds to replicate this experiment with food using several scent hounds? Of course, each dog needs to be tested separately so the pack mentality doesn't affect the results.

Richard, I ran my trials using the doubled freezer bags first. It didn't make any difference. After the first trial, my dog did investigate the OP sack, but walked away after a single sniff. In all trials the dog was in another room while I got things ready.

Ike, the kibble had already been in the single freezer bags for 2-3 weeks. It was because I could clearly smell it myself when walking into the room that I became concerned. I was afraid that if I could smell it that clearly, my dog would attack his pack! I ran the trials two days in a row, so the second day the second freezer bag and the OP sack had been in use for about 24 hours. A week or two would have been better. However, in the field three weeks later, my dog showed no interest until the kibble packages came out of the OP sack at feeding time. Nor did he sniff around his pack during the trip, or during subsequent trips.

Ben Pearre
(fugue137) - MLife
Science! on 04/11/2013 13:51:51 MDT Print View

Wonderful work!

This test shows that the bags are permeable to the "illicit" molecules to the point that there's easily enough scent for a trained dog to detect at close range, because the search times are similar. Right? Or does the fact that there were DNFs suggest that the dogs are close to their perception threshold?

Are the times taken by the dogs similar to times taken to find un-bagged goods? That would suggest that (a) the bags do nothing or (b) the times taken are not a great measure of effectiveness.

I'd be curious to see whether bags decrease detection range or probability or etc, and this study doesn't do much to convince me that that won't happen--it defies common sense (but then, so do the data on bike helmets; I'm willing to be told that my common sense is wrong). But then, I haven't encountered many bears--do they just come to where the humans are and then nose around? Or do they smell food from far away? If the former, then perhaps this experiment is more valuable than if the latter?

And how about non-bears? It can be useful to avoid attracting other critters. Does this experiment show that bags won't help there either?

Scott Toraason
OPSA:K on 04/11/2013 14:11:53 MDT Print View

Where were the OPSAKs obtained for the study?

Bill S
Re: Opsaks on 04/11/2013 16:36:09 MDT Print View

In bear avoidance, I would distinguish between avoiding *detection* due to scent, and minimizing attraction due to the same. What this study shows is it's almost impossible to avoid detection.

Even if you want to quibble with the details of the study, it should remind us just how *extremely* sensitive a bear's nose is. When you're dealing with an animal that can smell food--or even the tiniest food residue-- from miles and miles and miles away, isn't that kind of daunting and humbling to any effort you might make to conceal your food's scent? Once you really start to think about everything we touch during a typical day--even a day of hiking--you pretty quickly come to the conclusion that you're covered with food residue.

No matter how careful you are, you've gotten something food-like or smellable on you, surely, at some point during the day. All it takes is a speck. Just touching food and then brushing your hand against your bag or yourself an hour later would be enough to register a scent at this level of sensitivity. So it's just not realistic to expect that you'll defeat the bear's nose. It's just not. In my sleeping bag in the woods at night, when I think that I am really just making myself feel better.

Most bear avoidance strategies take two approaches:

1) Reduce the scent you're giving off to make yourself less attractive to the bear.


2) Physically prevent the bear from getting to your food in some way. e.g.,, bear bag it, put it in a canister.

If you're being realistic, you don't spend too much time worrying about 1.

Almost all of us smell like food when we go to sleep in the woods, but only a few of us have bear encounters at night or otherwise because of it. We don't know if that's because there's a certain threshhold we crossed--because we smelled *too much* or because of some other opportunistic factor. A lot of the objections to the study argue that there's a threshhold level of smell, and that OP sacks help you avoid that threshhold. To me the jury is still out on that after this study. We still don't know for certain if the OP sacks help you *smell less*, and if that makes any difference. The dogs may have smelled the OP sacks as quickly as the ziploc bags because they were both giving off enough of an odor to make them easily and straightforwardly detectable by a dog's super-nose. But that doesn't mean the OP sack isn't less odorous at a very granular level--and it doesn't tell us if that level of difference might make the bear less inclined to wander into camp.

All I know from my own experience at this point is that why we have bear encounters at night is always somewhat mysterious, because I know that I always smell, but only once in a while do bears wander in to check me out. So ultimately I have to rely on (2), creating a physical barrier to my food, in order to assure it is safe. If what I am really worried about is getting killed by the bear once it wanders in to camp for my food, (2) won't help me with that, but assuming I survive the encounter and the bear doesn't defeat the protection system, I'll still have my food in the morning. In part, the intense interest in the topic is probably because we're afraid of bears, period, and avoiding detection is so important because it assures us we won't have an encounter in the first place.

Edited by pnchike on 04/11/2013 16:47:40 MDT.

Stephen Barber
(grampa) - MLife

Locale: SoCal
Dogs, bears and mice on 04/11/2013 16:42:06 MDT Print View

What this study shows, bottom line, is O[dor]p[roof] Saks . . .


bags on 04/11/2013 20:58:12 MDT Print View

Im not sure the study shows anything conclusive. It suggests something, for sure. But further work would be warranted.

Personally, I am quite sure none of the bags are 100% odorproof, I would call any claim to such as false anyway. All plastics are permeable, to some molecules, to some small extent. It is only a matter of time and concentration.

That said, it is very unexpected that simple ziplocks would be statistically no better than more impervious plastics. This does suggest some problem with the testing protocol.

Not to mention that illicit drugs, are not the same as food. Different chemical species involved. Entirely likely that some chemicals are more able to permeate the plastics than others. Perhaps the drug of choice contained a particularly aggressive permeant for the bag material.

There was no control that proved that the loading process did not contaminate the outside of the bags.

The assumption seemed to be made that the only way to contaminate the bags with the odors of the illicit substances, would be to actually touch them with something contaminated.

Not true at all. Odors are vapors, humans can smell ppm quantities of certain things. Dogs can smell quantities so small, we cannot fathom it. The finest scientific instrument cannot even begin to approach a dogs nose.

Simply having odor resistant bags in the vicinity of the samples, even while loading, could have contaminated the outside of them all to the point the dogs could detect them all.