Vacuum sealers have a myriad of uses. They work well in reducing the volume of the things you carry in your pack....but be careful when you use them to pack food. They are great for excluding oxygen from those bacteria that require it to live but there are a large number of bacteria that do not require oxygen, live quite well in an oxygen free environment, and are even harmed by the presence of small amounts of oxygen. These are generally spore formers, a truly nasty one being botulism! (Clostridium botulinum, sorry taxonomists, I don't know how to underline or apply italics to this genus/species!). This spore former is bug whose toxin is lethal at even small amounts. Vacuum packing is great when used in conjunction with the temperature range the food inside normally requires, i.e. refrigeration, freezing, etc. or for packing dry foods like flour, pasta, other low moisture, shelf stable items. Never use vacuum packing in lieu of refrigeration -- you'll be sorry!
Bruce Woodbury