Refrigerated containers (usually -30^oC to 30⁰C) for temperature sensitive cargo; perishables (Vegetables, fruits etc.) Reefer units are not designed to reduce the temperature of cargo, but maintain the existing cooled temperature (chilled/frozen/controlled temperature) of the goods while shipping. Maintain better fresh air circulation, specially need for perishables as they produce gases which can damage cargo. Humidity control equipment remove accumulated water inside the container which can be a potential threat.