ISO shipping containers or refrigerated containers are shipping containers that are used for intermodal freight transport, which require refrigeration of temperature controlled cargo. ISO shipping containers have integrated refrigeration units that runs from an external electric power supplies from land based sites, container ships or from quays. When transportation is over land/road the ISO shipping containers will be powered from diesel powered generators, which are hooked up to the container while they are travelling. Some ISO shipping containers are water cooled, and these systems are used when the container is stored in a vessel without adequate ventilation. Another type of refrigeration uses CO2 for cooling. ISO shipping containers using CO2 cooling systems are able to keep the cargo frozen solid for up to 30 days. There are many types of ISO shipping container available for different purposes. ISO shipping containers that use refrigeration are commonly referred to as reefers or just refrigerated containers. The impact of ISO shipping containers on society is huge, and consumers all over the world enjoy the benefits of fresh produce as a result of them.