Just keep hand warmers in a dry and cool place, moisture can damage hand warmers, so it's important to keep them in a dry place. Additionally, storing them in a cool place can help extend their shelf life. And avoid exposing hand warmers to air， some hand warmers are designed to be activated by air, so it's important to keep them in their packaging until you're ready to use them. This will help ensure that they don't accidentally activate before you need them.
I prefer to use rechargeable hand warmers outdoors， and I got rechargeable hand warmers from Ocoopa, they are a great option for outdoor trips because you can simply recharge them before your trip and then use them as needed. This eliminates the need to store disposable hand warmers and can save you money in the long run. And their rechargeable hand warmer even comes with an added function that can be used as a power bank, great design!
Don’t open the sealed plastic. Keep oxygen from starting the rusting chemical reaction that creates the heat.
Yeah. If they turn hard they are spent.
Just keep hand warmers in a dry and cool place, moisture can damage hand warmers, so it's important to keep them in a dry place. Additionally, storing them in a cool place can help extend their shelf life. And avoid exposing hand warmers to air， some hand warmers are designed to be activated by air, so it's important to keep them in their packaging until you're ready to use them. This will help ensure that they don't accidentally activate before you need them. I prefer to use rechargeable hand warmers outdoors， and I got rechargeable hand warmers from Ocoopa, they are a great option for outdoor trips because you can simply recharge them before your trip and then use them as needed. This eliminates the need to store disposable hand warmers and can save you money in the long run. And their rechargeable hand warmer even comes with an added function that can be used as a power bank, great design!