This Hi-Performance Pak is non-toxic, non-hazardous, and re-usable and outperforms standard gel packs. The Engel Cooler Pak makes for a great cooler companion to keep contents cold and dry. Works great in lunch boxes, beach coolers, soft sided coolers and cold shipping. It also works well to extend the life of traditional bagged ice. Enjoy your recreational sports without the mess of melted ice. The Engel Cooler Pak is a non-toxic, non-hazardous, chemical freezer pack capable of maintaining a sub-zero temperature “charge” in a freezer or other insulated environment for an extended period of time. This is accomplished by charging the pack (freezing @ 32° C) to initiate the simple chemical reaction within the pack. The pack immediately begins to absorb energy (heat) and emit sub-zero temperatures once environment temperatures begin to rise. These packs are safe, environmentally friendly and re-usable up to five years! Therefore, the Engel Cooler Pak’s are a great alternative for gas emitting dry ice as our pack do not require special handling, training or costly haz-mat shipping fees.