History of Refrigerant Gases in Data Centers

May 28, 2025 6 min read By Noxtel

In Precision Air Conditioners: A journey from R-12 to HFOs

Precision air conditioners are essential for keeping data centers cool and running smoothly.

This equipment, designed to control temperature and humidity with accuracy, depends on direct expansion (DX) systems that use refrigerant gases to absorb and release heat.

But have you ever wondered what gases are used, how they have changed over time, and why?

In this article, we tell you the history of refrigerants in precision DX equipment, from their beginnings to the most modern ones, with a touch of environmental context and the standards that have guided these changes. Join us on this journey!

The pioneers: CFCs and the birth of modern refrigeration

In the 1930s, refrigeration took a giant leap with chlorofluorocarbons (CFCs), a game-changing invention. These gases, like R-12, were stable, non-toxic, and efficient, ideal for early air conditioning systems, including those that would evolve into precision equipment for data centers.

R-12 Chronology: Introduced in 1931 by DuPont under the Freon brand, R-12 dominated for decades. Its ability to absorb heat made it perfect for DX systems, which cool the air directly with a refrigerant. However, in the 1970s, scientists discovered that CFCs destroyed the ozone layer. 😱 The Montreal Protocol (1987) marked its death sentence, phasing out its use gradually. By 1996, R-12 was out of circulation in new equipment in most countries.
Why was it phased out? In addition to damaging the ozone layer, CFCs had a high Ozone Depletion Potential (ODP) and a high Global Warming Potential (GWP), making them unsustainable in the face of new environmental regulations.
What replaced it? Hydrochlorofluorocarbons (HCFCs), such as R-22, took over as a less harmful option for the ozone layer.

The transition: HCFCs and the reign of R-22

With CFCs in retreat, HCFCs became the new star. R-22, in particular, became the standard for precision air conditioners in the 1980s and 1990s. This gas was friendlier to the ozone layer (its ODP was much lower than that of R-12), but it was not without its problems.

R-22 Chronology: Introduced in the 1950s, R-22 quickly became popular. According to ASHRAE Standard 34, which regulates refrigerant nomenclature, R-22 was an HCFC with good energy efficiency and versatility. However, the Montreal Protocol also put it in the crosshairs, and by 2010, its use in new equipment was banned in many countries, with a complete phase-out scheduled for 2030.
Why was it phased out? Although less harmful than CFCs, R-22 still had a significant ODP and a moderate GWP (around 1810). Environmental regulations, such as the European Union’s F-Gas Regulation, drove its replacement to reduce climate impact.
What replaced it? Hydrofluorocarbons (HFCs), such as R-410A and R-134a, arrived as the next generation of refrigerants.

The HFC era: R-410A, R-134a, and the rise of efficiency

With HCFCs in decline, HFCs became the solution for DX systems in the 2000s. These gases did not damage the ozone layer (ODP = 0), making them ideal for complying with the Montreal Protocol. In precision air conditioners, R-410A and R-134a became the favorites.

R-410A Chronology: Launched in the 1990s, R-410A was designed as a direct replacement for R-22. According to Vertiv, this HFC offered greater efficiency in DX systems, allowing for more compact and powerful equipment. However, its high GWP (2088) put it under scrutiny with the arrival of regulations such as the Kigali Amendment (2016), which seeks to reduce high climate impact gases.
R-134a Chronology: Also introduced in the 1990s, R-134a was ideal for medium-temperature applications in data centers. Its GWP (1430) was lower than that of R-410A, but still high. Its use remains common, but it is being replaced in new equipment due to F-Gas Regulation restrictions.
Why are they being phased out? HFCs have a high GWP, which contributes to global warming. The Kigali Amendment and the F-Gas Regulation (updated in 2024) require reducing the use of gases with a GWP greater than 150 in many applications by 2030.
What is replacing them? Hydrofluoroolefins (HFOs) and low-GWP blends, such as R-1234yf and R-1234ze, are taking the stage.

The present and the future: HFOs and the green revolution

Today, HFOs represent the vanguard in refrigerants for precision air conditioners. These gases have an extremely low GWP and do not damage the ozone layer, aligning with global sustainability goals. In addition, manufacturers are exploring HFC and HFO blends to balance efficiency and environmental compliance.

R-1234yf and R-1234ze Chronology: Introduced in the 2010s, these HFOs are low-GWP alternatives to R-134a. According to Caloryfrio, R-1234yf has a GWP of 4, and R-1234ze has a GWP of less than 7, making them ideal for complying with the F-Gas Regulation. Although their efficiency is slightly lower, advances in DX equipment design have compensated for this difference.
Why are they the future? HFOs comply with the strictest environmental standards, such as those of ASHRAE and the F-Gas Regulation. In addition, their low flammability (A2L classification according to ASHRAE Standard 34) makes them safe for critical applications such as data centers.
Challenges: HFOs are more expensive and require adjustments in equipment, such as optimized compressors and valves. However, the pressure to reduce emissions is driving their adoption.

The role of ASHRAE and environmental standards

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has been key in this history. Its Standard 34, created in 1956 and adopted by ANSI, standardized the nomenclature of refrigerants, facilitating their identification and regulation. For example, the prefix “R” followed by a number (such as R-410A) indicates the chemical composition of the gas, helping technicians and manufacturers work with clarity.

ASHRAE has also influenced cooling practices. Since 2004, its thermal guidelines for data centers have expanded the acceptable ranges of temperature and humidity, reducing the need for excessive cooling and encouraging more efficient equipment that uses modern refrigerants. In 2015, ASHRAE recommended operating data centers between 18°C and 27°C with up to 60% relative humidity, which has allowed the use of HFOs in DX systems with greater flexibility.

On the other hand, regulations such as the Montreal Protocol, the Kigali Amendment, and the F-Gas Regulation have set the pace of change. These laws have forced the industry to innovate, moving from CFCs to HCFCs, HFCs, and now to HFOs, with a clear focus on reducing environmental impact.

Summary: Comparison of refrigerants

Refrigerant	Type	Year of introduction	GWP	ODP	Reason for phase-out	Replacement
R-12	CFC	1931	~10,900	High	Damage to the ozone layer	R-22
R-22	HCFC	1950	1,810	Moderate	Damage to the ozone layer	R-410A, R-134a
R-410A	HFC	1990	2,088	0	High GWP	R-1234yf, R-1234ze
R-134a	HFC	1990	1,430	0	High GWP	R-1234yf, R-1234ze
R-1234yf	HFO	2010	4	0	In use	–
R-1234ze	HFO	2010	<7	0	In use	–

Conclusion: A cooler and more sustainable future

The history of refrigerants in precision air conditioners is a reflection of how technology and environmental awareness have evolved together. From CFCs that damaged the ozone layer to HFOs that promise a greener future, every change has been driven by the need to protect our planet. Thanks to standards such as those of ASHRAE and international regulations, data centers can continue to operate without sacrificing the environment. So, the next time you walk into a nice cool data center, remember that there is a whole story behind that cold air! 😎

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