Shipping warmers are an optional add on for anyone living in a freezing area. Air plants can quickly die when exposed to freezing temperatures and these heat packs are designed to help keep the contents of your package warm for 72 hours. There is no guarantee that your plants will not freeze in very extreme temperatures, however, heat packs significantly increase the likelihood that your plants will arrive in good shape. If your order will be shipped through an area experiencing cold weather, it is advised to add on at least one heat pack. Multiple heat packs are recommended for larger orders. Anytime you are shipping air plants to an extremely cold destination, please arrange to receive your package right away rather than having it left outside, in a lock box, etc. Leaving your air plants out in freezing weather can kill them, even if it is only for 20 minutes. Heat packs are environmentally safe with non-toxic ingredients. They can be disposed of with normal trash.