Forum Index » Editor's Roundtable » How Safe Is Your Food? Investigating the effectiveness of odor-proof bags


Display Avatars Sort By:
Mitchell Rossman
(bigmitch) - M

Locale: Minneapolis-St. Paul
Re: Food Bags on 04/10/2013 12:47:11 MDT Print View

Very good study!

As a Ph.D. Chemist, I find this problem to be very interesting.

However, if you did develop a truly odor-proof bag, you might get a visit from your local DEA agent.

Walter Carrington
(Snowleopard) - M

Locale: Mass.
Odor proof bags: nylofume, hunter's scent proof bags vs contractor bags. on 04/10/2013 12:50:52 MDT Print View

Many thanks for doing this careful study.

I have asthma and am very sensitive to some chemicals used for cleaning. I've put my clothes in nylofume, hunter's scent proof bags and black plastic garbage and contractor bags to prevent my clothes from picking up these odors when traveling. The nylofume and hunter's scent proof bags are much better than other plastic bags at keeping out chemical odors -- the odor detector was my [human] nose. So odor proof bags reduce the odors passing through. On the other hand, it is impossible for a hiker to be as careful as the experimenters to avoid contaminating the outside of the bag.

But I doubt that this makes much difference for food bags versus bears. I think most of our guesses on how well various tactics work is based on our experience of human abilities. Dogs or bears have abilities that are difficult for humans to really comprehend.

Edited by Snowleopard on 04/10/2013 12:52:37 MDT.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: How Safe Is Your Food? Investigating the effectiveness of odor-proof bags on 04/10/2013 13:15:33 MDT Print View

Many years ago, before we had bear canisters in Yosemite, we had to hang our backpacker food at night. Still, the black bears knew where to look, and they climbed the trees to pursue the Mountain House prey. We were looking for a way to mask the food odor, so we started using moth balls. We would place a moth ball in the top of each food bag that was hung in the tree. For a while, it looked like that was going to work. Then some black bear stumbled onto the food anyway, and it got a good whiff of the moth balls. So then it associated food smell with the smell of moth balls, so the moth balls became more of an odor attractant than a mask. The entire experiment was a failure.

--B.G.--

Kirk Nichols
(kirknichols) - M

Locale: Intermountain West, Alaska
How Safe Is Your Food? Investigating the effectiveness of odor-proof bags on 04/10/2013 13:47:08 MDT Print View

Reynolds Oven baking bags are Mylar. I have human nose tested them and no one (human friends) could detect the freshly ground coffee inside though they could smell the grounds through six layers of zip-lock bags. Are the dogs available for another round of testing?Food bags inside an electric bear fence The food bags in the image are inside an electric bear fence that runs on one "D" cell.

Edited by kirknichols on 04/10/2013 13:49:31 MDT.

Stephen Barber
(grampa) - MLife

Locale: SoCal
non-odor proof bags on 04/10/2013 13:48:59 MDT Print View

Rob and Herbert: You're right, I'm wrong on specific molecules dispersion rates. The test doesn't measure absolute rates.

However, the fact that both bags remain detectable by a critter that has only 1/7th the sensitivity of a bear (according to some reports) strongly suggests to me that the difference in real life is minimal. Smells do seem to penetrate the ziplock more quickly than the OpSak, but both are penetrated and dispersed.

This is the first time I've seen OpSak vs ziplock bags actually tested in a controlled situation. Anecdotes are interesting and suggestive for more(controlled) experiments. This test bears (again the pun!) more weight to me than a ton of anecdotes, to the end that, given the permeability of the OpSak bag, its poor seal and its expense, I will not be buying or using anymore until further testing shows the OpSak or its improved offspring to actually block odors. The OpSak's minimal usefulness in blocking odors is not something I care to rely on.

Neither I nor my dogs have ever noticed any difference between ziplocks and OpSaks re smells.

YMMV.



The anecdote regarding metal covered plastic bags is interesting - there's a good line to follow up with testing and development.

Ike Jutkowitz
(Ike) - M

Locale: Central Michigan
General comments, scent theory, and some specific answers on 04/10/2013 13:57:50 MDT Print View

Lots of great discussion points!

Some general comments: Remember that this study is an experimental model. It is left up to the individual reader to determine how applicable he or she feels the results are to their intended use of the product. Using this model, we were not able to demonstrate any differences between the odor-proof bags and ziplocs. This doesn't mean that there aren't any. As discussed in the article, the dogs work at close range and are trained to signal on even minute amounts of the substances in question.

On the other hand, I have yet to see any strong scientific evidence to suggest that the bags do work any better than ziplocs. Without that proof, and with reasonable evidence to the contrary, why should I blindly believe the theory?

In the end, I believe that our conclusion was appropriate and not overstated. The bags are not 100% odor-proof as advertised. Not only did the dogs find them, but even long after the bags had been removed, dogs would repeatedly signal on the open lockers that had previously held study bags. Scent had been transmitted to the immediate environment.

Specific responses:
@Kyle- thank you for the kind words. I agree that proximity is a limitation of the study. However, the dogs' range is much longer than you think. The handlers like to talk about scent cones. Picture a 3 dimensional structure, heaviest at the source, and radiating outward in a cone-like pattern. The dogs are not actually searching for the object locker by locker as we would do, but instead run laps until they intersect the scent cone. It is very obvious when this happens as their behavior suddenly changes and they practically fall over themselves in their hurry to reverse direction and follow the cone. Study bags contained as little as 5 grams of scent, and as described earlier, this was vacuum sealed in freezer (foodsaver) bags, then wrapped in heavy canvas, then sealed in the study bag. So we are already talking about a trace quantity of scent that is doubly wrapped. Despite this, we saw the dogs hit scent cones from 10-15 feet away. Then they'd run straight to the appropriate locker. How big would the scent cone be when we are talking about 3-5 pounds of food, a stinky odor source approximately 320x larger than what we used and carried by the wind? I'm guessing it would be a pretty large cone.

@Luke and Jay- see my first post in this thread and the details above. Vacuum sealed freezer bags did not prevent odor transmission.

@John- we did not assess the nylafume bags, but may yet do so in an upcoming larger scale study. However, after this pilot study, my enthusiasm for doing so is low. I went into this first study not knowing what we would find (to the officers' credit, they never doubted the dogs for a second). Now that I've seen the dogs at work, I have little hope that a pack liner with a giant hole in the top would have any chance. We are hoping to look at some heat sealable mylar bags, but I will include a couple other odor-proof options if we can do so without making the project too cumbersome for the dogs and handlers.

@Rob, Bill, Stephen, and Herbert- Interesting discussion. We used the timed trials in our model to hopefully pick up on subtle differences between ziplocks and odor-proof bags, and were unable to detect a difference. To definitively answer your question, I think a large scale in situ study is probably needed.

@Redmonk- No false positives. When they knew, they knew, and they would bark and hit the lockers until acknowledged.

@Kirk- heat sealed mylar will be evaluated hopefully next month.

I appreciate all the comments and feedback even if, in the interest of space, I have not responded personally. Thanks again.

J P
(jpovs) - F - M
Re: General comments, scent theory, and some specific answers on 04/10/2013 14:45:36 MDT Print View

I had some stinky spoiled food that was very evident when I placed it inside a ziplock. I then placed it inside a Opsack and the smell was significantly reduced.
Opsacks are not 100% oder proof, but they do reduce the scent significantly versus Ziplock. With my experience using Opsacks, I would still buy and recomend them.

Edited by jpovs on 04/18/2013 14:55:14 MDT.

Richard Colfack
(richfax) - MLife

Locale: ARIZONA
OPSAK on 04/10/2013 15:01:22 MDT Print View

Excellent article. No longer will I waste good money on OPSAKs. I've always been unimpressed with their durability and despise the crappy closure (not too mention their ridiculously high cost for a Ziploc bag) but I always put up with this thinking it helped keep bears from slaughtering me in the tent.

Roleigh Martin
(marti124) - MLife

Locale: Moderator-JohnMuirTrail Yahoo Group
Bruce, thanks for the posting about anti-static bags on 04/10/2013 15:06:15 MDT Print View

Bruce, thanks for the posting about anti-static bags.

I looked at UsPlastic.com web site for choices. The anti-static bag choices are here:

http://www.usplastic.com/catalog/item.aspx?itemid=24643&catid=883

Postscript: I see there are two types of anti-static bags, those that are poly-based and those that are aluminum based. Uline has the aluminum based ones here:
http://www.uline.com/BL_57/No-Print-Static-Shielding-Bags-Reclosable

I wonder how these anti-static bags compare with biohazard specimen bags.

http://www.usplastic.com/catalog/item.aspx?itemid=75825&catid=883

The Nyloflume bags look interesting but I see (a) that you should always use two of them, per recommendation, and secondly, they do not have a ziplock. A good ordering place is here though:

http://www.quantumtermite.com/termite-products-and-paperwork/nylofume-bags-20
http://www.carnivalfumes.com/nylofume_bags.pdf

In all 3 alternative bag choices. It would be nice to know which of the 4 (the 4th being OP bags) work best. 4 and 5 if you distinguish between the two types of anti-static bags.

Edited by marti124 on 04/10/2013 15:18:28 MDT.

James Marco
(jamesdmarco) - MLife

Locale: Finger Lakes
How Safe Is Your Food? Investigating the effectiveness of odor-proof bags on 04/10/2013 15:25:49 MDT Print View

Dr. Jutkowitz, just to close any potential avenues of debate, I would have expected a set of empty bags be included in the same search tests, to eliminate the possibility that the dogs were keying on the plastic smell, latex smell, perhaps the powder on the latex of the bags themselves or something else the experimenters were doing to the bags unintentionally...a mere quibble.

Regardless of the dispersive effect of gases, I think it is safe to say that reliance on OP sacks as the first line of defense against bears is probably not a good thing. Even if a perfect seal, with no scents of edibles on the outside of the bag, could be managed at home or during packing, it would be impossible to maintain in the field. Coupled with the far better sense of smell, usually rated between 2 and 20 times better than a dogs, depending on who you are listening to, and, the rather lengthy time in which foods are normally hung, about 7 hours or about the average sleeping time for a person and usually at night when vision is usually not the primary sense, I do not believe dispersion to be much of a consideration. If the OP sack leaks, it likely leaks enough to be smelled by proximal bears, black or brown. If the dispersive area drops from (an example only) from say 50' to 25' it would reduce the area in which a bear would detect it by about 2/3, but NOT prevent him from breaking into and eating your food. This is more absolute or boolean, he has it or he doesn't. Hey, ha, I prefer NOT to play statistical games with my stomach..."I have food or I don't" doesn't really make sense, only "I have food." I completely agree with your conclusion.

Ike Jutkowitz
(Ike) - M

Locale: Central Michigan
Re: latex on 04/10/2013 15:38:17 MDT Print View

James- I agree that a no-drug control would have been a great addition. As far as the dogs cuing in on latex scent, this is a vet school student locker room. Lockers and lockers full of latex gloves, plastic bags, dog smells, medicinal smells, etc

Edited by Ike on 04/10/2013 16:02:34 MDT.

Randall Raziano
(rrazian) - MLife

Locale: SW Colorado
Excellent Review. on 04/10/2013 15:54:06 MDT Print View

I was surprised by the result, and this will directly impact the steps I take to avoid bear encounters. Thank you!

rogerio brito
(kafer4life) - MLife

Locale: North Country
Man you guys Rock!! on 04/10/2013 16:05:41 MDT Print View

Wow, I seem to have fallen to the victim of good marketing. Good thing I am cheap and bought them at a discount away from big box stores and with a discount. Well at least they will keep everything dry until I finally get around to making my Cuben food bag. Thanks guys a great read either way. Since I already own them I might as well continue to use them for the slightest bit of extra help they may give.

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: How Safe Is Your Food? Investigating the effectiveness of odor-proof bags on 04/10/2013 16:24:10 MDT Print View

Great article!

Another thought about bears -- hike were they ain't. In other words avoid popular areas where bears know how to find an easy meal.

Bruce Warren
(Aimee) - F - MLife
Re: Bruce, thanks for the posting about anti-static bags on 04/10/2013 16:45:43 MDT Print View

Roleigh,

I just remembered I also had Oscar test military MREs. They are packaged in thick aluminum foil/plastic bags. Oscar the Raccoon just walked all over them... oblivious to the delicacies inside. You can burn up the empty MRE bags with a little bit of aluminum foil remaining that you can carry out. If you carry only MREs no animals will bother your camp site... all they will smell is your stinky human body. Bear canisters are only a physical barrier... I do not like putting my food far away from my tent... kinda risky if far from home. My son recently did 1,300 miles on the PCT and used a Bear Vault where required... but he kept all smellables in anti-static bags inside the Bear Vault near his bivy.

Years ago I made some food cans out of metal paint cans and did lots of testing. I watched two bears walk by my tent up in the mountains at Philmont Scout Ranch. They ignored the two full food cans sitting there.... I painted them camo so they looked like tree stumps. Nothing leaks out of a good old fashioned metal paint can unless the lid seal gets dented or rusty. Last year I opened a virgin 35 year DuPont Lucite paint can left over from when I first painted my house. The paint was totally fine. The design of the classic metal pry-off paint can lid is amazing... so simple but delivers a totally hermetic seal. Same with food tin cans. Keep them dry and the beans inside will last a hundred years or more. Because nothing goes in or out thru steel.

Keeping food residue off the outside of your camping food container is very important. I wipe them down with hand sanitizer or stove fuel (alcohol).

Herbert Sitz
(hes)

Locale: Pacific NW
Re: How Safe Is Your Food? Investigating the effectiveness of odor-proof bags on 04/10/2013 16:54:40 MDT Print View

I think James raises a couple interesting points.

James M. said, " I think it is safe to say that reliance on OP sacks as the first line of defense against bears is probably not a good thing."

Although I'm skeptical of conclusions people seem to be drawing regarding complete inefficacy of OPSAKs, I wouldn't think of (and I don't think many others do think of) OPSAKs as "first line of defense". The _first_ line of defense is the food hang, which if done properly can thwart even bears that know there's food in it. Preventing bears from smelling the food hang is definitely secondary, though I'd like to do it if I can.

James M. said, "If the OP sack leaks, it likely leaks enough to be smelled by proximal bears, black or brown. If the dispersive area drops from (an example only) from say 50' to 25' it would reduce the area in which a bear would detect it by about 2/3, but NOT prevent him from breaking into and eating your food."

James throws out 25' and 50', but I'm curious what we should take to be "proximal" bears. I've questioned conclusions people are drawing because I think by "proximal" we should maybe be thinking several hundred yards, or a quarter- or half-mile. Granted, the BPL test may provide evidence that we might expect bears to smell both OPSAK and ziploc at 25'. But what if bears can smell ziploc contents at half-mile and the comparable OPSAK only at 50 yards? Pretty big difference, and I don't see that the BPL test tells us much at all about that.

A quick check indicates that bear density in Sierras is on order of 0.5 to 1.0 bears per square mile. (California Bear Population) Densest area I've been is Quinault River area on southwest side of Olympic National Park, where density may be around 4 bears per square mile. (Black bears in Quinault Indian Reservation)

What are the odds a bear is going to randomly wander within, say, 100 yards of your food hang? (Perhaps high in some cases, low in others.) Are properly used OPSAKs with food smellable by bears 100 yards away? Is a ziploc with your food smellable 100 yards away? I don't know, but BPL close range test results notwithstanding I would place my bets on the OPSAK being harder for the bear to detect than ziploc at a distance of 100 yards or more. Maybe the distance is more, maybe it's less, would be good to know. (But again since OPSAK is a secondary defense I don't see it as critical to food safety. It's just something that's helpful to a food hang, increases odds that bear won't identify and try to get to your food.)

John Nausieda
(Meander) - MLife

Locale: PNW
Re: Re: Bruce, thanks for the posting about anti-static bags on 04/10/2013 17:23:10 MDT Print View

The steel paint can sounds very promising.Super cheap and a great seal. A question remains about how it is lined?I too have old latex which looks good but there is O2 in there when half full. Is it BPA free? Do the plastic cans that hold wallboard compound work as well? Has anyone cooked in a steel paint can ?

Edited by Meander on 04/10/2013 17:25:23 MDT.

James Marco
(jamesdmarco) - MLife

Locale: Finger Lakes
Re: Re: How Safe Is Your Food? Investigating the effectiveness of odor-proof bags on 04/10/2013 18:20:58 MDT Print View

"It's just something that's helpful to a food hang, increases odds that bear won't identify and try to get to your food."

Herbert,
Yes, I think we can both agree that smell based deterance is probably not necessary and at best will reduce the "foot print" a food bag or canister will impart to the environment. The first statement was a bit of an understatement laced sparingly with sarcasim indicating reverse logic. Sorry, it was a bust and was not meant to be taken quite so literally.

Well "proximal" can mean many things. To some, it can mean the tent walls. To others a half mile. In this context it is fairly specific. Any distance the bear can detect the odor through the OP sack. It really does not matter what that distance is.

Kevin Flynn
(kmflynn_01) - MLife
Great Study! on 04/10/2013 21:14:16 MDT Print View

Excellent!
I bought a few OPsaks a couple of years ago and after they tore apart while opening them I went back to double bagging ziplocks. I've never regretted it, not had a problem.
I have both bear canisters and ursacks in which I place my zippies - glad to know what I've always suspected - that the opsak/loksaks were mostly hype.

Rick Burtt
(rburtt) - MLife
Nylofume or anti-static on 04/10/2013 21:31:49 MDT Print View

Really interesting article. Beyond the obvious results, my experience with OPSAKs has been negative just based on built quality. I've had seams blow out too often to trust these bags. I bought some nylofume bags that I haven't tried yet and am now considering anti-static bags, but so far I lack any true scientific data. I may do my own experiment with my dog who behaves like a bear - I dare not leave my food bin out unattended or she treats it as her own personal smorgasbord!