LOKSAK OPSAK bags are made of heavy-duty plastic and have a hermetic seal. When closed, the bag is airtight, waterproof, and odor-proof (the “OP” in OPSAK).
On some trips, I use the 12″ x 20″ size ($6, 1.5 oz) as a lone food sack or as a liner inside a wildlife-resistant Ursack. I also like the 9″ x 10″ size, which holds my daytime snacks and which I keep near the top of my pack.
Review: LOKSAK OPSAK
LOKSAK OPSAK bags are tough, lightweight, and reasonably priced. Inside the 12” x 20” size, I can fit about five days of food. Less ravenous hikers can probably fit six.
The rectangular shape packs efficiently inside my pack, and its width fits perfectly a snack/sandwich bag, candy bar, and most energy bars. Because it is made of transparent film, the contents can be easily seen. The seal seems to blow out after 4-6 weeks, but I continue to use them for many months afterwards.
On its own, an OPSAK is an inadequate method of overnight food protection. It’s best considered an enhancement to a more reliable method, by reducing food odors.
Most specifically, an OPSAK can be used to line an Ursack Major or Ursack Minor to make it less detectable or less interesting to a bear or rodent. Maybe that black bear two miles away won’t smell it, or maybe it’ll decide to visit a different campsite that is giving off stronger food odors.
If I’m using a hard-sided canister, I do not use an OPSAK as well. Canisters are not entirely bear- or idiot-proof, but I’m very confident in them as a standalone food storage method.
I never hang my food from bears, because I think other methods are more effective (e.g. canisters), or at least equally effective and easier (e.g. the Ursack Major). If you do hang your food, an OPSAK could add value to the system.
I will use an OPSAK on its own only if there is low risk (or, ideally, no risk) of bear or rodent activity at my campsites. And I will sleep with it — on it or immediately next to it, or keep it inside my shelter. I wouldn’t leave an OPSAK unattended even at “safe” campsites.
Is an OPSAK really odorproof?
Fresh out of its packaging, an OPSAK is both odor-proof and odor-free. After a few days of use, the OPSAK is probably still odor-proof (i.e. food smells do not permeate outside the bag), but I suspect its exterior becomes contaminated with food smells due to normal handling.
Bears have an extraordinary sense of smell — seven times better than that of a bloodhound, according to Yosemite — and I would imagine that this contamination puts the OPSAK on a bear’s radar. However, the food smell is probably no stronger than the food smell on your clothes or your shelter, and that level of food smell is generally not considered to reach the threshold for action. (Philmont would be a notable exception.)
To reduce food odor contamination, an OPSAK could be washed between uses with soap and water.
The transparent body material is heavy-duty and will withstand months of use. On my 6-month Alaska-Yukon Expedition, on which I used the OPSAK exclusively for food storage, I replaced them only twice (so two months per bag) and got several more months out of each bag on subsequent trips. Rips or tears in the body can be easily fixed with duct tape or Tenacious Tape.
The airtight seal has proven less durable, with an average lifespan of four to six weeks. After the seal blows out, I just close it up like a potato chip bag. I think this is “good enough” — if I thought that leaking food odors could make the difference, I should be using a more guaranteed food storage method anyway, e.g. hard-sided canister.
Do you have questions about or an experience with OPSAK bags? Leave a comment.
Disclosure. I strive to offer field-tested and trustworthy information, insights, and advice. I have no financial affiliations with or interests in any brands or products, and I do not publish sponsored content
This website is supported by affiliate marketing, whereby for referral traffic I receive a small commission from select vendors like Amazon or REI, at no cost to the reader.