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 (freezing @ -18C) 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. Additionally, our Phase Change Technology provides superior performance to traditional gel-packs that are water based and have a much sharper temperature discharge rate.