The Last Ice Pack You Will Ever Need! 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. -The-Phase Change Technology provides superior performance to traditional gel-packs that are water based and have a much sharper temperature discharge rate. They are-capable of maintaining a sub-zero temperature -charge- in a freezer or other insulated environment for an extended period of times, that well exceeds that of blue ice, ice packs, bagged ice or any other ice substitute. Nu-Ice recommends turning freezer to coldest position or use of a chest freezer to obtain a full charge.