Poler makes the only heat bags that are air activated and come in their own resealable pouch. You can turn them on and off by simply putting them back in the pouch and sealing them. Use them as often as you like for a total of 10 hours, then keep the bag and use it for something else. They are non toxic. Properly sealed, these heat bags have a shelf life of about 2 weeks once opened. They take about 10-15 minutes to heat up and cool down each time you use them. Heat bags are designed to be used in gloves or pockets, which is where they get hot.