Refrigerated containers are available as both 20ft or 40ft units as well as High Cube options and are used primarily to ship foodstuffs and pharmaceuticals. When activated and plugged into a diesel genererator or genset they can keep cargo at a constant temperature from door to door, this is described as operational. They can be used at temperatures from plus 25 to minus 25 degrees centigrade.
Remote monitoring is now offered by some shipping lines. The recorders can monitor vital information such as temperature and transmit it to the line during the journey. The remote systems can even change the settings if required.
The containers can also be used as non-operational refrigerated containers as they are insulated and will stop cargo temperatures fluctuating in extreme heat or cold.
They will keep cargo at a constant temperature.
They have less capacity due to the insulation.
They are expensive to operate.
They are not always available as they are considered specialist equipment.