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Everything You've Ever Wanted to Know About Refrigerant

If you have an air conditioning unit, then you're likely familiar with refrigerant. This chemical is responsible for cooling your home down during the height of summer, keeping your fruits and vegetables fresh in your fridge, and even maintaining a comfortable temperature in your car.

Without coolant, our lives would look very different. Ice boxes were a wonder of their time, but they're certainly not a convenient way to keep milk from spoiling.

At Aire Serv, we know everything there is to know about refrigerant. Whether you're wondering about where coolant comes from, how it actually works, or how to check its levels in your AC unit, we have the answers.

What is Refrigerant?

What exactly is refrigerant? In a nutshell, refrigerant is a chemical that can efficiently transform from a liquid to a gas, and back again. These unique properties make it an ideal substance to use in air conditioners, fridges and freezers. The chemical reaction that takes place to transform refrigerant carries heat and expels cool air (and vice versa). Refrigerant is also sometimes colloquially called Freon. While Freon is a type of coolant, it's actually a brand name. This is similar to calling tissues Kleenex, or calling cola, Coke.

What is Refrigerant Made Of?

This cooling chemical can be made out of a variety of different substances. They can be synthetic and natural. Common coolants include;


Chlorofluorocarbons are man-made substances that contain carbon, chlorine and fluorine. CFCs are highly destructive to the environment, and are largely responsible for depleting the ozone layer of Antarctica. CFCs have a very high GWP, or Global Warming Potential. Subsequently, most developed countries phased-out CFC production by 1996. Developing countries also phased-out CFC production by 2010.


Hydrochlorofluorocarbons are also man-made and consist of hydrogen, chlorine, fluorine and carbon. Essentially, HCFCs replaced CFCs once the latter was being phased-out because they are less harmful to the atmosphere. HCFCs are less stable in the lower atmosphere, enabling them to break down before reaching the ozone layer. That said, HCFCs are still considered a greenhouse gas and have a very high Global Warming Potential.


Hydrofluorocarbons are also a replacement for CFCs, and consist of hydrogen, fluorine and carbon. Since HFCs don't include chlorine or bromine, it doesn't deplete the ozone layer. Yet, HFCs are a greenhouse gas and have a high Global Warming Potential.


Hydrocarbons are a simple chemical compound, consisting of hydrogen and carbon. Examples of hydrocarbons include methane, ethane, propane, butane and cyclopentane. HCs properties make them ideal refrigerants. However, HCs are highly flammable and must be carefully handled by manufacturers, installers and consumers. Inexpensive to produce, HCs do not deplete the ozone layer, have a low Global Warming Potential and have a low toxicity rating. The most commonly used HC for refrigerants is propane (usually found in commercial and industrial freezers, air conditioners and heat pumps) and isobutane (typically found in domestic refrigerators and freezers).

How Does It Work?

Coolant works by undergoing a chemical reaction as it passes through an air conditioner's three main parts: a condenser, a compressor and an evaporator. It starts in the compressor as a gas, where it is highly pressurized (or compressed). This process turns refrigerant into a liquid. As it transforms, the chemical absorbs heat from your home. Then, it transitions to the condenser in your outdoor unit. Here, it expels the heat it has gathered with help from a blower motor. This is why AC units are hot on one side.

Once the heat has been expelled, coolant moves into the evaporator. Here, it "evaporates," and is returned to a gas. This process creates a drop in temperature and cools the coils within your indoor unit. A fan blows air over the coils, creating cold air for your home. After this step, coolant returns to the condenser and turns into a liquid. The process begins once more.

What Are the Different Types?

We've established the different chemical compounds that comprise coolant, but there are actually specific types of refrigerant that have different uses.

What is R12?

The original CFC refrigerant, R12 was once used in everything from home air conditioning units and fridges to automobiles. It was invented in the 1920s and was used in homes until the 1950s, after which R22 became the most popular compound. However, R12 continued to be used in cars until 1994. At this time, the Environmental Protection Agency mandated that all new vehicles use R134A instead. Since it's a CFC compound, R12 refrigerant significantly depletes the ozone layer. It has since been phased out of use.

What is R22?

In the 1950s, R22 took over from R12 as the leading refrigerant of choice for residential AC units and fridges. It didn't cause as much wear on compressors, and didn't need as large of pipes to flow through. While R22 is still widely used in America, it's an HCFC compound. While it doesn't deplete the ozone layer, there are still environmental concerns regarding its use. R22 is a greenhouse gas, and has a very high Global Warming Potential. In fact, in 2020 the United States Environmental Protection Agency mandated that only recycled or stockpiled R22 coolants be used.

What is R410A?

R410A is a chlorine-free coolant that meets the United States Environmental Protection Agency's strict environmental guidelines. It was developed in 1991 and does not deplete the ozone layer. As an HFC, it's better for the environment than R22 or R12, but is still considered a greenhouse gas. Additionally, R410A is more energy efficient than R22 as it allows for higher heat transfer. For residences with air conditioners that use R410A, homeowners are also able to save a bit on their energy bills while doing better by the environment. It's important to note that R401A cannot be used in machines designed to use R22.

What is R134A?

Created to replace R12, R134A does not deplete the ozone layer, but is a greenhouse gas. Is used in automobiles as well as in commercial and domestic fridges and freezers. As an HFC refrigerant, it doesn't deplete the ozone layer and meets the United States Environmental Protection Agency's stringent guidelines.

What is R410A?

A non-ozone depleting HFC refrigerant, R410A is more energy efficient than R22. Most importantly, it does not emit greenhouse gases into the environment. It's commonly used in air conditioners and commercial refrigeration and chilling units. Like R401A, this compound also can't be used in machines that were designed for R22 coolant. However, if you buy a new AC unit, it's likely it will use R410A.

What is R404A?

Also a safe alternative to R22, this HFC compound is usually found in refrigeration systems that have a temperature range of -49° F and 59° F. This range makes it an ideal compound for industrial and commercial transport industries. Be mindful if ever using R404A Coolant, as touching it can cause frostbite.

What is R407C?

This HFC compound has thermodynamic properties and is commonly used to replace coolant in equipment that used R22. It can work in ductless split systems, packaged air conditioners, water chillers and refrigeration systems with a medium temperature range. It is also commonly found in new refrigeration systems and appliances.

How Was Coolant Invented?

Initially, refrigerant was created to help preserve food. But it has since been adapted as a cooling agent found in air conditioners—which is where our expert HVAC technicians deal with it the most. That said, there were various scientific pursuits that led to the creation of refrigerant. Discover its fascinating history by reading the following.

In Ancient Times...

Humans have sought to preserve food since as early as 500 B.C. At this time, ancient man used ice houses to keep food cool. These "houses" stored ice harvested from nearby frozen lakes and rivers. They. kept ice cool as long as possible. Ice houses were kept cool by being built deep into the earth.


Basic means of refrigeration, such as ice houses, remained the norm for thousands of years. It wasn't until the 1740s when Scottish scientist William Cullen invented the first form of artificial refrigeration. Cullen illustrated—in theory—how rapidly heating a liquid to a gas can create a cooling effect—which is still the premise for modern cooling appliances. While Cullen never put his idea into practice, he laid the foundation for other scientists to build off his idea.


This year marked an important stepping stone for refrigeration development. Thomas Moore, an American businessman, invented an icebox used to cool dairy products in transport. He initially called this invention a "refrigeratory," until he patented "refrigerator' in 1803.

Industrialization also rose during the 1800s, and subsequently, so did urbanization. With more and more Americans living in cities, expanding the distance between food source and consumer, there came a growing need for refrigeration.


Another momentous year for refrigeration, at this time American inventor Jacob Perkins built the world's first working vapor-compression cooling system. His prototype worked by using ether in a closed cycle; it wasn't successful commercially. However, his design was a concrete step toward modern fridges.


The first residential ice boxes were made by carpenters, and designed to take advantage of regular ice deliveries to American homes. Essentially, ice boxes were insulated wooden boxes lined with tin or zinc. Below was a drip pan that collected melted water.

However, using ice sourced from a lake or river was beginning to cause a wide range of health problems because of increased pollution due to the industrial age. Instead, manufacturers looked to mechanically making ice—which also led the way for electric fridges and freezers.


In this year, German engineering professor Carl von Linde patented the process of liquefying gas. His findings led to inventing the first compressed-ammonia fridge. This invention was momentous, as refrigeration was quick to replace ice as a means to preserve food commercially.


American Engineer Willis Carrier borrowed from the concepts of mechanical refrigeration to develop the first modern air conditioner. His system sent air through coils filled with cold water, cooling air while removing moisture to help control room humidity.


American Fred W. Wolf invented the first residential electric refrigerator in 1913. It was called the Domelre, or the DOMestic ELectric REfrigerator. Unfortunately, his design was not a success—but another of his inventions, the ice cube tray, became very popular.

1915 to 1918

Scarcely five years later, things in the refrigeration realm were really starting to take off. American Alfred Mellowes invented a self-contained refrigerator in 1915, with a built-in compressor. To mass produce fridges based on Mellowes' design, William C. Durant started the Frigidaire Company. Meanwhile, the Kelvinator Company introduced a fridge that used automatic control.


While electric fridges were not mass-produced in a modern sense, they were available to wealthy families. In 1926, roughly 200,000 fridges had been sold. By the mid 1930s, this number would jump to around 6 million. Also during the '20s, General Electric introduced the "Motor-Top," which became the first fridge to see widespread use. However, these fridges used sulfur dioxide or methyl formate as refrigerant. These highly toxic substances would eventually lead to Freon's invention in 1929.


Carrier, who was credited with inventing the first modern air conditioner 20 years earlier, improved his system and wound up also inventing the centrifugal chiller. This machine added a central compressor and replaced ammonia with a more effective and less dangerous fluid, dichloroethylene, which enabled air conditioning systems to become more widespread and appear in department stores, hotels and movie theaters.


Freon was invented in 1929, and the following decade saw a subsequent major expansion in cooling systems and appliances.


The 1940 Packard was the first car to offer factory-installed air conditioning. By 1969, more than half of all new cars sold were equipped with built-in AC. In this decade, home freezers sold as separate compartments were introduced as frozen foods became a commonplace commodity.


WWII saw a slow in both the development of refrigeration appliances and AC systems. However, full mass production of modern fridges began as the war ended.


By the early 1950s, air conditioning became usual in private homes and businesses. As the decades passed, refrigeration appliances and systems continued to be found in residential and commercial properties, until becoming the essential services we expect in homes and businesses today.

How to Check the Refrigerant Level of an AC Unit

The only sure way to check your AC unit's refrigerant levels is with help from a professional HVAC technician, as it involves dissembling the machine and taking its temperature. This can be very difficult if you don't have the right tools or experience. However, there are a few signs that your system may be low on refrigerant. If you notice any of these red flags, call one of our professional technicians right away.

  • Your air conditioner is blowing out hot air.

  • The coolant line has ice on it.

  • You hear a hissing or bubbling noise.

Need Help With Your AC Unit? Call the Experts at Aire Serv!

Now you're equipped with everything you need to know about refrigerant, you're almost as educated as our technicians! Except, that is, when it comes to air conditioner repair and installation. Should you need help with an AC unit that's not working properly, or you want to install a more updated model to reduce use of R22 coolant, book an appointment with your local technician. We're here to help!