Bought a dehydrator for the first time had no clue how to use these packets. I opened the package, not knowing that you have to put it immediately back into an airtight container again. Went to google how to store dry foods on the internet - when I came back, the whole bag was warm! I panicked and thought I was going to burn the house down - or, that it might explode! I am not a chemist and have long forgotten anything I've ever learned from high school. Had to go back and google how to use these things! I wish the package had large warning labels, or IMPORTANT PLEASE READ instructions in the box - if it did, I didn't see it. I need bifocals and couldn't read whatever little prints are on the package. Now, am not too certain if they're still good or not. I used a few with some dry cereal and i heard the jars pop and seal. Am glad to learn about these handy little packs though, will find them most useful. Since my sweetie died I've had more time to think about things that I've taken for granted all our life. I guess we were out enjoying out lives too much and didn't realize this as an option. I'm looking forward to dehydrating oranges, bananas, fruits, vegetable chips, jerky, herbs and teas; of course for storing my sugar, flour, rice beans. Over all my 30+ married life, have thrown away so much food because never stored anything properly. Flour would sit on my shelf that I would use once or twice - then, it would taste horrible after several months of non-use, I end up throwing it all away. This should preserve the life of my dry foods much longer. A much appreciated product that I wish I'd of used years ago! Looking forward to canning and preserving more foods throughout the rest of my life.