Introduction
Keeping your food safe from wildlife is an important consideration on any camping trip, and assumes even greater importance when traveling through bear country. Historically, options for food protection have included food hangs and bear-resistant canisters or sacks. Food hangs or “bear bagging” can be technically challenging, requiring that the food bag be suspended at least 12-15 feet above the ground and 8 feet from the trunk of nearby trees. Bears frequently foil these hangs by climbing out on the supporting branch to access the food, or by breaking the branch off using their body weight. Bear canisters are highly effective at deterring hungry bears, but do not prevent them from being attracted to the campsite. Additionally, these canisters can add considerable bulk and weight to a backpacker’s load.
Learn about bear canister use, design, and performance in our latest BearVault 500 (BV500) Review.
In recent years, a number of odor-proof bags have been marketed with the backpacker in mind. These are typically made from heavy-duty polyethylene or nylon polymer and are advertised as waterproof, airproof, and odor-proof. Odor-proof claims are apparently derived from anecdotal experiences, testimonials, and tests of oxygen gas transmission rates through the plastic film that the bag is made of. An extensive Internet search did not turn up any unbiased scientific studies evaluating the effectiveness of these bags in preventing odor transmission.
As an emergency and critical care veterinarian at a university hospital, I’ve gotten to know some of the officers in K9 units pretty well over the years. One day, I was talking to one of the officers, and the conversation turned, as it often does, to ways that people have tried to outsmart the dogs using a variety of scent masking strategies. Strong odors like coffee, “scent lock” hunting products, and even concealment in sealed steel containers had proven no match for the dogs. I asked about odor-proof bags. The officer had never heard of them but was more than willing to put them to the test. And so, the idea for a study was born.
Based on manufacturer claims that the bags were 100% odor-proof, we hypothesized that the odor-proof bags would prevent dogs from detecting substances hidden within, or at the very least would greatly delay their identification. To test this hypothesis, we planned to run a series of timed searches for scent pouches hidden within odor-proof bags1. Ordinary supermarket ziplock bags2 would be used for the control group. Because the dogs were not trained to find salami or cheese, the “scent” for the study would consist of eight pouches of illicit substances used for dog training. These would be divided between the study groups such that each of the four odor-proof bags would have a matched ziplock control containing a similar type and quantity of scent. Four police dogs were available to participate in the study, and each would perform searches for all eight of the study bags for a total of 32 searches. For data analysis, we would compare the number of bags found in each group and the average time it would take for the dogs to find the bags, if they could, in fact, find them.
Study Design
We conducted the study in the women’s locker room at the university. This was one of the largest rooms available, and the uniform rows of lockers would allow the bags to be concealed without visual clues for dogs or officers. Because some of the lockers had locks and others did not, we put ‘dummy’ locks on a number of the lockers used in the study to ensure that the officers would not focus their dog’s attention on only unlocked lockers.
Four odor-proof bags and four ziplock bags were prepared as described above. Bags were numbered from 1-8 for identification purposes. To avoid transferring scents to the exterior of any bag, one gloved investigator held open each bag while an officer dropped in the scent packet. The bag was sealed and handed off to a third person to check the seal. The bags were then allowed to sit undisturbed for 30 minutes to allow scents to permeate the bags. During the study, a new pair of gloves was put on before handling any study bag to avoid cross-contamination.
Before beginning, one dog and handler team conducted a locker-room search to rule out the possibility of drugs on site that were not part of the study. This step concerned me during study design, and I was greatly relieved when it was over. No students were implicated in the making of this study.
Study bags were now hidden two at a time, each in their own aisle, and allowed to sit for 5 minutes to establish a scent trail. One dog was then brought in and instructed to search. Dogs were timed from the initiation of the search until they definitively signaled a find. They then moved on to the next aisle to search for the second bag. The officer was permitted to terminate the search if he felt that the dog had adequately searched the aisle and would become frustrated if forced to continue.
It was anticipated that the longer the drugs sat, the more scent would permeate the bags, potentially making them easier to find. Consequently, bags were presented to each dog in random order to avoid giving an advantage to any particular bag. To minimize the effect of study bag location on search duration, the locker room was divided into two zones, zone 1 (10-30 ft from starting position) and zone 2 (40-60 ft from starting position). Each odor-proof bag and its respective control (the ziplock bag containing the matching type and quantity of scent) were hidden in the same zone.
Officers were blinded to the contents of the lockers to avoid having the dogs look to them for cues. After each successful search, dogs were rewarded with their favorite toy and taken from the room. The study bags were removed from their lockers, and the doors were left ajar to minimize confusion due to lingering scents. The room was then reset for the next search. This strategy of swapping lockers and study bags between searches, as opposed to having the dogs search for each bag in the same location, was implemented at the recommendation of the canine handlers to avoid the possibility of one dog following another’s scent trail to the bags.
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Discussion
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I'm in the food packaging industry, and just saw this timely article touting a new aroma barrier bag by OdorNo. The company website offers no insight concerning the technology used or data to compare with other options, but I thought I would mention it for consideration. However, the more I read about the little that the company actually says it leaves a bad taste in my mouth.
http://www.odorno.com/
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Here are some quotes from a separate article…
http://www.plasticsnews.com/article/20130416/NEWS/130419930/odorno-bag-eliminates-smell-and-distributors-are-buying-it#
"Not even a dog can smell through my bags," said the colorful Fortune, between laughs and smiles as he demonstrated his product's effectiveness."
"Amazon.com has already begun to order them from us,"
…
Daniel, it's an excellent one–the gold standard for the issue. FWIW, I also found the author very easy to interact with. I emailed him about a question I had regarding his research, and he replied back within a day or so.
Daniel, I concur with Clayton's opinion. Steven Herrero is probably the most preeminent expert on the griz. His studies seem very scientific and well designed. Also, his writing is quite readable. For further info about the brown bear, check out the Craighead family. They were pioneering griz studies in Yellowstone (and Glacier) back in the 60s-70s. They were also scholars, being based at the University of Montana. They have been a bit controversial, but they did a good deal of valid research. There are numerous books about the griz, but Herrero and the Craigheads pretty much stick to science, with little anecdotal conjecture thrown in.
I enjoyed your article and I appreciate the time and effort you put in to the project. I don't enjoy bear encounters when I am in camp. Even a cat circling my camp at night can get me a little edgy. I think I have been lucky, but not all have been so lucky and this is in a state with no Grizz. Just because someone did not die in their tent from injuries from a black bear encounter and make Wikipedia does not allow me to take the critters for granted. Congratulations on generating a flurry of comments and I look forward to reading more of your articles.
It may not prevent a bear from getting my food, but wow they do a great job of keeping ME from smelling the hot n spicy cheez its in my entire pack and on all my gear.
Lots of food and other items seem to be supplied in packaging with aluminum foil liner as well. I have always figured that cut down on permeation.
Tuna
Toothpaste
etc.
I made the mistake once, and only once, of putting a bit of toothpaste in a tiny ziplock.
Everything in my pack smelled like toothpaste, like the ziplock wasnt even there. It was horrible. I can say, ziplocks are super duper permeable by comparison.
nice article.
it has been my experience that peanuts will stink directly thru a ziplock, but cashews and almonds will not display anything like that sort of thing.
tide laundry detergent will also go right thru its bag, and into MY food.
the stuff from trader joe's does not do that nearly as much.
story :
once upon a time outside of jasper alberta i chanced to buy a whole large packet of pepperoni, which i soon opened and rebagged. it was Good and Hot pepperoni, and once opened you could smell it not only outside it;s bag, but outside the pack !
omg… so .. i ate it.
ALL of it.
it burned going down. and it burned going out.
yee haw !
cheers,
v.
Here in Oz it used to be traditional – like dead normal, that all gear smelt of sausage. Instant tribal ID.
Cheers
Well, I guess I'll use a bear canister so I don't train the bear but honestly I probably smell like everything that I'm storing. I brush my teeth with smelly toothpaste, I probably wipe my hands on my pants or food smell is transferred to my walking sticks, the wrapper to my Pro-Bar is in my pocket until I stop for dinner and put it in the trashbag in my bearikade, the steam of my cooking meatloaf is probably in my wool shirt.
This local story reminded me of your testing. I wonder if it’s really smell they use for phones or (ultrasonic) sound? To smell it while inside a ziploc under water is quite a feat.
I know I'm playing necromancer in reviving an old thread, but this was some might good research work!!
I've used OP sacks for the last 10 years (at least) in the Sierra Nevada backcountry on annual trips. They were used in conjunction with an Ursack as final protection. On at least 4 occasions when bears were IN OUR Group's CAMPSITE the bears failed to detect the food I had; my food was taken by me as a supplement to the group's food. The latter was stored in aluminum panniers ("bear boxes" if you will) used now by all mulepackers in the Sierras. So it might have distracted the bears from detecting my food, since there was no attempt to conceal the contained food's odors, as I did with the OP Sacks. On many other occasions there was no evidence or knowledge of a bear's presence during the night, but we were in areas notorious for bears along the John Muir Trail, such as at or near Thousand Island Lake, Lake Ediza, Glen Aulin, (and ALL other sites on the Yosemite High Sierra Camp Loop), Rock Creek (Cottonwood Pass region), Cottonwood Lakes, Rae Lakes, Paradise Valley and other sites on the Rae Lakes Loop (this included one of the episodes of a bear in camp attacking the aluminum bear boxes but ignoring my stash) or East Lake. Indeed, I've not had my stash moved at all suggesting a bear had tried to get the food but gave up. I might add that my food was always some distance away from the aluminum boxes containing the group's food, which I would think would lessen the "distraction" factor sited above.
So the bears ain't got my food yet.
David E.
I definitely felt like my Opsack did a better job of containing food odor then regular ziplocks. It made me feel a lot better in grizzly country.
I've read that bears actually have pretty good eye sight so I work under the assumption that if the bear is close enough to see my bear bag he'll probably investigate whether he can small it or not. I try to rig my bear bag in a place that is not super visible. In the feature I'll probably take a stuff sack for my bear bag that is either camo or a low visibility color like brown or gray. I don't want an orange sack that sticks out like a sore thumb.
My theory is that an Opsack is better then nothing especially if a bear is a couple hundred yards away and he hasn't seen my food bag or my shelter.
As a follow-up to my posting above: I just spent 4 consequtive weeks in the Sierra Nevada backcountry with my OP sacks concealing my food against bears and other wildlife. Nary a nibble; on the other hand, there was no evidence of bears being in the vicinity, or at least no obvious bear attempts on our camp food which was stored in aluminum bear boxes carried by mules. Also, the frequent presence of mules may well have kept ursines away.
David E.
Anyone know if the second study that Ike mentioned ever occurred?
Sorry Trace. Dealing with some personal stuff at the moment. It's on the back burner for now, but I'll keep you posted.
I would think that masking the odors would be more effective than trying to contain them. You could try something like powdered sulphur or spray a Ursack with OdoBan Bitter Barrier. I know our cat takes one lick of the Bitter Barrier and never returns.
Plastics are actually porous to scent particles so they can escape by being absorbed into the plastic and then released on the other side the longer the scent is in the plastic container the more scent diffuses though.
However metal containers are not porous so scent particles cannot diffuse through it can only excape at the joins/ openings.
Thickness of material comes into the equation. The thicker the material and/ or the more layers there are then the longer it takes for the scent to diffuse into the outside air.
It may be possible to mask the scent of the food by including a very strong smelling, potentially displeasing substance in one of the outer layers.
I’d love to see a test that includes Nylofume/Nylobarrier bags, or even the BaseCamp bags that you can get at Amazon or WalMart. These bags are made to be closed with the twist, fold, and twist-tie method, and that seems a lot more secure and odorproof than the zip on the OPSack.
I mean, if there truly were a plastic ziploc bag that masked odors from dogs (which are way less blessed in the olfactory department) why in the world wouldn't they be the hit of the drug smuggling community?
That's all I have to say.
How do you know they aren't?
Because turkey bags are cheaper. Local favorites method.
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