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HomeEducationWhat is a reefer container and how does it work..??

What is a reefer container and how does it work..??

image for reefer container


Simply put, reefer containers are big fridges that are used to transport temperature controlled cargoes such as fruits, meat, fish, seafood, vegetables, dairy and also also non-food products such as flowers, pharmaceuticals and film across many miles and oceans..

Some cargoes may need to be shipped chilled or frozen or in controlled + temperatures. Reefer containers have the ability to maintain the cargo at the required temperatures for the duration of the transit.

How does a reefer container work..??

Image for T bars
Image from CMA-CGM Reefer Brochure

Reefer containers are bottom air delivery units designed to distribute chilled air from the floor, via specific T-shaped decking, with the advantage of producing a consistent and uniform flow of air across the entire shipment, powerful enough to ensure a perfect air exchange with the goods.

Refrigerated units can maintain or lower the temperature of your shipment, even in the most difficult conditions.

Reefer containers also equipped to ‘warm up’ the goods for those shipments where required, with the ability to maintain temperatures up to 30°C when required, regardless of outside temperatures.

Important point to note is that a reefer unit is not designed to reduce the temperature of the cargo but rather to maintain the pre-cooled cargo temperature.

The airflow requirements of each commodity varies and there is no one size fits all in reefer cargo movement..

Example :

  • in the case of chilled cargo, air has to flow through the cargo at all times so that heat and gases are removed, therefore the cartons used should have ventilation
  • in the case of frozen cargo, air has to flow around the cargo so there should be no gaps between the cargo and the walls and the cargo itself, so the cargo has to be block stowed

Cold Treatment

Due to some fruit types carrying potential pathogens, some importing countries like China, Japan, Nigeria, require cold treatment of the fruit (colloquially known as Steri shipments).

For these kind of shipments, the fruit will be pre-cooled to a lower temperature than a commercial market and in order to monitor this, steri probes (about 3 per shipment) are inserted into the pulp of the fruit, within the carton.

There is a minimal tolerance allowed in temperature variance. Should the tolerance be exceeded, then either additional hours or days will be required to bring it to the required temperature.

Should one of the probes drift above the tolerance, the cargo will be rejected at country of destination, due to the potential of the fruit still retaining pathogens.

All in all, cold-treatment cargoes follow the normal pattern of shipping with one or two additional requirements.

Should the units be packed correctly and cargo post harvest process followed, barring the unit failing, cargo can be received by the customer on a ready to eat basis or even for further storage.

Checklist for stowage of reefer cargo

image for checklistSome general tips on stowage of reefer cargo :

  • Cargo should not be stuffed beyond the end of the T-floor
  • Cargo should not be stuffed above the red load line
  • Cargo must be stable on the floor and tightly wedged so it doesn’t shift during passage
  • Unit must always be set at the proper carrying temperature and this set temperature will vary according to the cargo being loaded
  • Dehumidification controls must be checked
  • If pre-cooling is required, it must be the cargo that is pre-cooled and not the container, unless the container is loaded in an airlocked cold tunnel in the cold storage
  • Ventilation setting is of utmost importance and must be set at the correct level
  • As air will follow the path of least resistance, there should not be any restrictions for air flow and any gaps between the pallets and the doors must be closed using cardboard or even wood. This will then force the air to circulate correctly and reduce the potential for heat sinks (warm air continuously circulating) near the doors

Stowage Principles

image for reefer cross section
Image from CMA-CGM Reefer Brochure

Below image shows the cargo stowage principles that needs to be followed when packing a reefer container.

  1. Refrigeration unit
  2. Boxes do not extend beyond pallet
  3. Deck board spacing allows vertical airflow
  4. Boxes vented for vertical airflow
  5. Pallet load is secured
  6. Rear doors
  7. Air space above cargo
  8. Airflow
  9. Box vents aligned

There are various makes of reefers with the most common being Carrier, Thermoking & Daikin.

Have you had any experiences due to not following above stowage principles..?? Do share if you have had any experiences..

This article written in conjunction with Donovan Smith a Reefer expert based in South Africa.

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Hariesh Manaadiar
Hariesh Manaadiar
I am Hariesh Manaadiar, the Founder of Shipping and Freight Resource.. I have been in the dynamic shipping and freight industry for over three decades and have worked in several sectors.. I share my experiences and knowledge of the industry through this blog for those looking for help in the industry.. Stay subscribed for more free useful content about shipping, freight, maritime, logistics, supply chain and trade..


  1. Hello,
    Manufactured with MS corrugated sheets on exterior and plastisol coated sheets for interior, these containers are extremely heavy duty. The corrugated outer sheets make the construction very robust in case of an accident.

  2. Good day,

    May I please ask for urgent information about space available on container ships for 40ft reefer containers please.

    We have stocked containers standing in port in China and cannot find space on container ships. These are items needed in South Africa by the end of October 2021.

    Are you able to assist please?

  3. I am looking to purchase a used reefer that I could maintain 65 degrees. It for experimentation of multi-tier farming. Where do I find used containers.

    • Hi Richard, am not sure which country you are in.. But every country will have container resellers.. But for reefers, I would encourage you to contact some of the shipping lines to see if they have any working but older reefers that they may consider selling.. some of them do offer..

  4. Hello Hariesh, I have two questions that I wanted to ask regarding this article:
    Firstly, how long does it take to repair leakage in a reefer container that causes loss of coolant and secondly, what causes loss of power in a reefer container.

  5. Once the Refrigerated Container is unplugged how long will it take to see a change in temperature. Will it change much in a 24 hour period

  6. Hi,

    I’d like to ship some expensive artwork on canvasses to Paris, but it will have to ship in the summer. what is the recommended temperature if I choose to ship in reefer container?

  7. Dear sir,
    Please I I produce ice cream and I do not have a freezing tunnel. I plan to acquire a ocean type reefer to employ both for deep freezing (-30) and fixed storage unit. Am I making a mistake or it’s ok.
    Ice cream exits the machine at 4 degrees Celsius and should harden up to – 30 while in storage.

  8. Please we need your advise on below during loading Cold Treatment Containers:

    1- If from the technical tasks to accept or reject the loading of cargo depend of the testing result or the technician is forced to load the cargo even if the cargo is not precooled?

    2- The technician can prevent the shipper from stuffing cargo in container if the cargo temp in cold store not reached to the protocol temp?

    3- In case of technician attending the shipper packinghouse and one or more of the 3 cargo random samples temperature is discovered to be not equal or below 2.2c,
    The Technician should to proceed in loading the cargo or to reject the stuffing and to stop the loading till the cargo retuned to the cold store for precooling again and then to stuff the cargo.

    4- Who has the responsibility to ensure that cargo is well precooled? And what happens if the cargo are not pre-cooled to the point of required treatment before loading?

    Finally, please advise what are the main tasks of the technician and responsibility when attending the shipper packinghouse for loading Cold Treatment containers.

    • Hola, quisiera saber que puede pasar con carga congelada a -20ºC si la transporto con generadores por servicio local y tengo que apagar los generadores todos los dias para recargar combustible aprox 2-3 hrs, tiempo de transporte 40 dias temperatura local 38-40ºC

  9. hello.i am from Mongolia. When should demurrage charge expire? i am importing goods from South America.And once container arrived in my country should demurrage expire at my responsibility? And freight company should takes care of it?

    • Hello Ider, as mentioned in my post about the difference between demurrage and detention, demurrage is generally considered for full containers and detention for empty containers.. However, this varies in different countries and I am not sure of what the practice is in Mongolia.. Generally the demurrage should stop once full container has been picked up and detention will then start till return of empty container to the nominated depot.. If it is combined demurrage/detention charge, then it will end once empty container is returned to the nominated depot..

  10. hi,
    we loaded 40 ft container,the cargo loaded below the red line and the door side we left very small gap.
    when release the cargo from loading buy it was future it will affect the temperature of cargo

  11. The storage power for a reefer container is calculated by the hour, how is the treatment of a reefer container plugged out at 1:15 am? Should the 15 minutes fraction be rounded up to 30 mins or one hour?

    Is there an international regulatory body that monitor and calibrate refrigerated containers?

  12. Due to the need to reposition reefer containers, as they mostly have a need one way only, light general cargo is sometimes loaded into a reefer container so that the shipping line can make some income from the repositioning and not have to send it back empty.
    It must also be remembered that a reefer container is not capable of freezing the cargo in the same manner as your freezer at home. The cargo must be at the required carrying temperature when loaded into the container.
    Priya, the T floor is that actual floor of the container where the cold air can circulate below the cargo. This T floor (channels) will end prior to the container door so no cargo must be packed close to the door as is possible with general purpose containers. The air needs to be able to circulate around the end of the cargo in the container. Take a visit to a container depot and have someone there show you the reefer container. It can be very interesting.

    • Transportation of Refrigerated cargo in containers has had significant impact on the supply chain. Discuss (to include international shipping policies, and international conventions and protocols).

  13. Hi ..d article n dis website is amazing ..I’m new to shipping ..Doin business management in shipping. .I find this article very useful …by the way can u tell me wat is T-floor


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