CO2 backup system will be rest when the refrigeration system normally works, and when there is a power failure, CO2 backup system will work by rechargeable batteries, and jets liquid phrase CO2 for refrigeration system at intervals tobackup system will work by rechargeable batteries, and jets liquid phrase CO2 for refrigeration system at intervals to reach the preset temperature. When there is a refrigeration system failure, press the Mandatory button, and backup system will work.