Review on WiseDry 100 Packs of 1-Gallon Mylar Bags (4 Mil, 15''x10'') with 300cc Oxygen Absorbers - Ideal for Storing Dehydrated Vegetables, Grains, Legumes, and Emergency Long-Term Food Supplies - Food Grade by Tiffany Love

Oxygen scavengers work properly. Make sure you put them in an airtight container (such as a rock jar) as soon as you open the package. When you're ready to seal your packs, open the mason jar, take out the required absorbers and seal the rest as quickly as possible. You have approximately 2 minutes to heat seal the Mylar bag before the absorbers begin to take effect. If you want to know what a bad oxygen scavenger is like, leave him alone. You will find that like a hand warmer it will start to heat up and harden. If the oxygen scavengers are malleable, they're still good. Just keep them sealed in an airtight container. The packages themselves are fine, just secure them with an iron or hair straightener.