Nu-Ice 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 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 Nu-Ice packs are a great alternative for gas emitting dry ice as our pack do not require special handling, training or costly haz-mat shipping fees. 2 lb.