The Role of the Air Cycle in the ULT Space Cooler Line: Safety and Environmental Responsibility at Ultra-Low Temperatures

The air cycle used in the ULT Space Cooler line is an important part of making sure that ultra-low-temperature cooling is safe and good for the environment.

The ultra-low temperature (ULT) market is changing because environmental rules are getting stricter and more people are paying attention to safety at work. Pharmaceuticals, biotechnology, research labs, and the storage of sensitive materials all need not only stable temperature control but also high operational reliability, environmental neutrality, and low risks for workers.

In this case, the air-cycle technology used in the ULT Space Cooler line is a different way of doing things in engineering. Air (R729) is the refrigerant in these systems. This is a big difference between them and traditional vapor-compression systems, and it needs to be looked at separately in terms of safety, environmental impact, and following the rules

Air (R729) as a Refrigerant: Legal and Physical Considerations

In traditional vapor-compression refrigeration systems, synthetic or natural refrigerants move around in a closed loop. These substances must follow rules about how to store, charge, monitor leaks, recover, and get rid of them, no matter where they came from. This is especially true for fluorinated gases (F-gases), which are becoming less common in many countries.

Air (R729) is the working medium in an air-cycle system. From an environmental point of view, it has these traits:
-0 GWP (no potential for global warming)
-0 ODP (no potential for ozone depletion)
-0 TFA (no formation of trifluoroacetic acid that lasts)

Even modern synthetic refrigerants with a lower GWP may still help make fluorinated compounds that last a long time. These compounds are getting more and more attention from regulators. When the limits on GWP and the amounts of F-gases that can be used are changed, using air gets rid of the need for regulation because air is not a controlled refrigerant.More rules are being put in place for refrigerants

Regulations in the refrigeration industry are getting stricter, especially when it comes to synthetic refrigerants. This trend can be seen in: lower limits on how much F-gas can be used; stricter rules for reporting leaks; mandatory training for employees; stricter rules for collecting and disposing of refrigerants; and new classifications of substances based on how toxic and flammable they are.

In ULT applications, even natural refrigerants like ammonia, hydrocarbons, and CO₂ need complicated engineering solutions. They might be toxic, catch fire, or work only under high pressure, which makes the design and operational requirements higher.

Systems that use air don't have these problems. They don't have any chemicals that are dangerous, toxic, or flammable, which makes the rules much easier to follow. This is especially important for places where the equipment lasts a long time, like pharmaceutical warehouses, research centers, and factories.

Getting rid of the risk of refrigerant leaks

One of the biggest problems with traditional refrigeration systems is that they can leak refrigerant. Possible effects depend on the type of refrigerant:
Toxic exposure (like ammonia), fire or explosion risks (like hydrocarbons), asphyxiation risks at high concentrations (like CO₂), environmental liability and mandatory reporting (like F-gases). In ULT systems, big differences in temperature and pressure put more stress on parts, which could make leaks more likely.

Air is the working medium in the ULT Space Cooler line. When the pressure drops, regular air from the atmosphere is let out into the environment.

This gets rid of: chemical dangers, the risk of fire or explosion, and the need for emergency plans for dangerous refrigerants.

Because of this, infrastructure needs may go down, such as the need for gas detection systems, explosion-proof zones, and special ventilation.

No Rules for Storing or Getting Rid of Refrigerant

Most of the time, traditional refrigeration systems include:
-getting refrigerant;

-storing cylinders or tanks;

-charging them in a controlled way;

-checking for leaks; recovering and getting rid of them.

Each of these steps makes things more expensive, harder to run, and requires more administrative oversight. Some countries require special permits and compliance with fire safety rules to store certain refrigerants.

Air-cycle systems do not need to buy, store, or get rid of refrigerant. After the system's service life is over, air doesn't need to be moved, stored, or processed in any special way. This makes things easier and lessens the administrative burden, especially at sites with little space or infrastructure that is far away.

Safety for workers and fewer steps in the process

In traditional refrigeration systems, workers do things like charge and recharge the refrigerant, test for leaks, maintain the compressor and refrigeration circuit, and keep an eye on the pressure and condition of the refrigerant.
To work with chemical refrigerants, you need special training and strict safety rules. Depending on the substance, there could be risks like chemical burns, exposure to toxic substances, or fire hazards.
MIRAI systems don't need to be charged with refrigerant. This: keeps people from coming into direct contact with dangerous substances; lowers the number of certifications needed for employees; and lowers the chance of accidents caused by human error.
Because of this, safety is built into the system instead of being the result of complicated compliance procedures.

As part of the process, air thermal treatment and purification

Another technical aspect of MIRAI systems is that the air that goes through the unit (like the MIRAI Cold 10) is heated and cleaned before it enters the cooled chamber.

This means that air circulation does two things at once:
-Making things cooler.
-Bringing clean, conditioned air into the storage space.

In traditional vapor-compression systems, the refrigerant moves in a closed loop and heat exchangers cool the air. The air in the chamber is cooled indirectly and not through the refrigeration cycle itself.

Airflow is a part of the thermodynamic process in an air-cycle system. This makes sure that there is clean, safe air, that there are no risks of contamination from refrigerant leaks, and that sensitive equipment and stored materials are less likely to be affected.
This could make operations more reliable when storing pharmaceutical products, biological samples, or valuable research materials.

Engineering Aspects of Functioning at Temperatures Below –40 °C

To get temperatures below –40 °C, most systems use cascade refrigeration or special refrigerants. This makes the equipment more complicated and puts more stress on the compressors and control systems.
The reverse Brayton cycle is what the air cycle is based on. It doesn't depend on phase changes between liquid and vapor like vapor-compression systems do. The adiabatic expansion of compressed air cools things down.
Some important engineering features are: no condensation or evaporation, stable working-medium properties over a wide range of temperatures, and predictable system behavior at very low temperatures.

In ULT applications, where reliability is very important, making the thermodynamic process simpler helps keep things stable over time.

Long-Term Sustainability and Independence from Rules

Most ULT cooling systems are made to last between 10 and 20 years. The rules may change a lot during this time. The history of F-gas regulation shows that some refrigerants can be limited or even banned completely.

When you use air as a refrigerant, you don't have to worry about: changes in quotas; possible future bans; changes in refrigerant prices; or supply problems.

In this case, being environmentally neutral is not a marketing advantage but a structural factor that lowers legal and regulatory risks for the entire time the equipment is in use.

In conclusion

As environmental and industrial standards get stricter, choosing a refrigerant becomes a strategic choice. This is especially true in the ultra-low-temperature market, where traditional solutions often come with more safety requirements and more complicated systems.

The ULT Space Cooler line uses air (R729) and the reverse Brayton cycle to get temperatures below –40 °C in a different way. The system is designed to be environmentally friendly and safe to use. It has zero GWP, ODP, and TFA values, no toxic or flammable substances, no need to store or dispose of refrigerants, improved safety for workers, and thermally treated air is sent to the storage chamber.

This method lets people see ULT cooling as not just a way to control temperature, but also as part of a larger plan for environmental and industrial responsibility in a time of stricter rules and higher sustainability standards.