What Is a Reefer Container? How Does It Work for Cold Storage?

Shipping fresh and frozen food, milk and wine, Seafood and processed food, vegetables and flowers, or Pharmaceutical and medical products across the world needs more than just a box container. It needs an insulated container that can keep products cold, fresh, and safe. That’s where a reefer container or insulated container comes in.

These containers are used daily across the world. They transport perishable goods at the right temperature setting in an unbroken cold chain distribution. Whether it’s meat from Argentina, bananas from Ecuador, or vaccines from Europe, reefers are vital.

In this guide, we’ll break down what a reefer container is, how it works, and why it’s important for cold storage.

What Exactly Is a Reefer Container?

A reefer container is a large shipping insulated container with a built-in cooling system. It is also known as “refrigerated container” for sea freight. These insulated containers are made to carry goods that need temperature control to stay cold or frozen during transportation. You’ll see them in ports, on ships, trains, and lorries globally.

Reefers come in standard sizes. Most are 20-foot or 40-foot long. High cube reefers are also common. These are a bit taller and can carry more goods. The outlooks like a regular steel container, but inside, it’s insulated and fitted with a refrigeration cooling system.

These containers don’t lower the temperature of goods from warm to cold. Instead, they keep ready-chilled items at a constant temperature. This means products must be cooled before loading, making them a dependable cold storage container.

Reefer Container Wide Variety of Applications.

Reefer containers are widely used in many industries. This is because reefer container is versatile in Sea, train and land transport. It can be transported by trailer with built-in genset and plug in supply in rail transportation as well. Their main job is to distribute perishable goods keeping them in an unbroken cold chain distribution. These include:

• Fresh fruit and vegetables
• Dairy like cheese, milk, and yoghurt
• Poultry and Seafood
• Frozen products and ice cream
• Flowers and processed food
• Medical and Pharmaceutical products such as vaccines, drugs and medical accessories
• Chemicals and other heat-sensitive components in the aerospace industry.

Besides shipping, reefers are also used for temporary temperature-controlled container setups. Businesses often rent them for events, festivals, construction sites, or emergency storage.

How Does a Reefer Container Work?

Let us examine the key features that distinguish a reefer container from a standard container.

Built-In Cooling Refrigeration System

A reefer container is equipped with a refrigeration unit mounted at one end, designed to maintain the internal temperature at the desired setting. The system distributes cold air through a T-floor, which features narrow gaps that allow airflow to circulate evenly from the bottom, ensuring uniform cooling of the cargo.

The refrigeration system is typically powered by shore electricity, operating on 3-phase, 415V, 50Hz supply. When the container is in transit, a generator set (genset) mounted on the trailer provides the necessary power to keep the unit running.

Temperature Control

Standard reefers operational temperatures range between +25°C and -40°C. That covers a wide range of products from chill to frozen goods. Thermo King also have special reefer containers, called the Super freezers, where temperature performance can reach as low as -70°C. These are used for a wide range of products such as perishable foods, poultry, seafood, medical and pharmaceutical products, fruits and vegetables, bakery and dough, and so on.

The Thermo King Temperature Controller provides advanced temperature monitoring system and error code feedback for easy maintenance and usage. The pretrip function provides quick checking before usage and regular service support. This ensures quality control on temperature performance for reliability and durability.

Ventilation and Airflow

Airflow inside the container must be smooth and consistent to maintain a uniform temperature throughout the cargo. For fresh produce such as fruits and vegetables, proper circulation also helps remove gases like ethylene, which can accelerate ripening.

To ensure effective cooling, the container should be packed in a way that allows air to circulate freely. Cargo must not be packed too tightly, but large empty gaps should also be avoided. Correct loading practices help prevent hot spots in the center of the load, keeping all products evenly cooled, fresh, and in good condition.

Humidity Control

Some reefers come with humidity settings. This feature is important for products like flowers, chocolate, or seeds. Too much moisture can cause mould or damage. Too little can dry out delicate goods.

Standard humidity levels in a reefer range from 60% to 85%, though some units can go as low as 50%.

Read More about Cold Chain Logistics

 

Drains

To stop water from building up, reefers have drains in the floor. These drains let out any moisture that collects from condensation. They’re built to keep water and insects from getting in from the outside.

How Is a Reefer Container Powered?

Reefer units need a constant power supply. They don’t use fuel or batteries but run on electricity. There are three main ways to power a reefer:

1. Port or Depot Power – At shipping terminals or warehouses, reefers are plugged into mains electricity using 3 phase, 415V 4 pins or 5 pins sockets.
2. Ship Power – On cargo ships, reefers are connected to onboard power sources.
3. Gensets – On the road, reefers rely on generator sets. These are fuel-powered devices fixed either to the trailer or the container. There are two kinds:
   • Clip-on genset – Mounted on the front or side of the container
   • Underslung genset – Attached below the trailer, mostly used for lorry transport

These keep the reefer powered when no plug-in power is available.

Other Cooling Methods

Most reefers work by air cooling. But there are other options such as blast freezer, dry ice, cool packs, Eutectic Plates and so on.

Water Cooling

Some reefers use water to remove heat. This is done when the container is in a place where air can’t circulate well, like below the deck on a ship. Pipes carry heat away using water. This system is less common today because it costs more and needs extra parts.

Cryogenic Cooling

In special cases, reefers may use dry ice or liquid nitrogen to stay cold. These gases cool the container as they evaporate. It’s often used for short trips or in air freight. These containers don’t need electric power, so they’re flexible. But they only stay cold for a limited time.

Monitoring the Goods

Today’s reefers come with smart tracking systems. They have built-in sensors and microprocessors that record:

• Supply and return air temperature
• Defrost cycles
• Set point changes
• Power on/off times
• GPS, Location and door sensor.

Some containers are equipped with cargo probes, which are placed directly inside the goods to measure the core temperature in real time.

The data from these probes can be accessed online through tracking tools, allowing companies to monitor both the container’s location and its operating condition. This visibility enables quick response if any issue arises, helping to protect the quality of the cargo.

What Is a Non-Operating Reefer (NOR)?

Sometimes reefers are used even when cooling isn’t needed. These are called non-operating reefers or NOR containers.

This happens when the container needs to return empty to its origin. Instead of sending it back without goods, it carries general cargo with the cooling turned off. It’s a good way to save costs and keep containers moving.

Can You Customize a Reefer Container?

Yes, reefers can be modified for many uses. Companies often ask for custom features like:

• Extra doors or side access
• Lights or racks inside
• Insulated floors
• Windows or vents
• Painted exteriors or company branding
• Temporary working office with window and air-conditioning

These custom reefers are useful for pop-up shops, mobile labs, event kitchens, or cold rooms on construction sites. You can also add alarms or remote monitoring tools for better control.

Some businesses even convert a container with freezer capability into a long-term storage unit on-site.

Final Thoughts

A reefer container is one of the most essential tools in the global cold chain distribution trade. It allows us to enjoy fresh strawberries in winter, deliver life-saving vaccines to hospitals, and transport seafood safely across oceans.

Built to be smart, durable, and reliable, reefer containers can be used on land, at sea, or even on-site for storage. Whether moving goods across continents or keeping them locally stored, they ensure perishable products remain safe, cool, fresh, and ready for use.

Monzone Group is a trusted name in supplying and customizing reefer containers. With 28 years of experience and a strong commitment to quality, Monzone supports businesses across industries to keep their cold chain operations running smoothly.

So the next time you see a shipping container with vents and a refrigeration unit (Thermo King system) at one end, you’ll know it’s a reefer—working quietly in the background to keep the world’s goods fresh.