Air Conditioners And Ozone Emission – Get The Facts

Conventional air conditioners do not generate ozone. However, air conditioner units with integrated ionizers do create and emit small amounts of ozone.  The ions produced by the ionizer component can split oxygen molecules, releasing them to bond with other oxygen molecules and form ozone.

While air conditioners help make a room comfortable on hot summer days, they can also release greenhouse gases due to the refrigerant. So let’s find out if using HCFCs, Freons, and other chemicals in air conditioners create ozone.  

Since more than 80% of all Americans use air conditioners, it’s crucial to know if they create toxic byproducts like ozone. At the same time, it is also essential to understand their role in the emission of greenhouse gases and ozone depletion. Read this article to find out all of this and more.  

  • Standard air conditioners do not produce ozone, however air conditioners with ionizer components do produce small amounts of ozone.
  • Ozone is produced when water or oxygen molecules are split. The oxygen is released, and is free to create ozone.
  • Air conditioners with in-built ionizers can split oxygen molecules causing ozone to be produced.

What Is Ozone?

Before we jump into air conditioner (AC) units and how some of them emit ozone, let’s first get into what ozone is and how it is normally formed.

Ozone (O3) is a gas that naturally occurs and forms a sort of protective sheath in the upper atmosphere (stratosphere).

This ozone layer absorbs harmful ultraviolet radiations, and protects us from the various side effects of UV rays and sun damage, like, skin cancer, cornea inflammation, aging, liver spots, actinic keratosis (dry, scaly skin patches), and solar elastosis (loss of skin elasticity and development of yellow, thick skin with deep wrinkles).  

Oxygen makes up 21% of Earth’s atmosphere and normally exists as two stable oxygen atoms (O2). However, ozone is made up of three oxygen atoms. The third atom in ozone (also known as nascent oxygen) makes it highly unstable, and it reacts with surrounding substances by donating one oxygen atom to them.

This reactive nature is why ozone is artificially produced for disinfection, air and water purification, pulp bleaching, and medicinal therapies.  

Artificial Production

Ozone is artificially produced by using high voltage or UV light exposure to split water molecules. As a result, the water releases an oxygen atom that goes on to bind with other oxygen molecules to form ozone. This is how ozone generators create the gas to disinfect water and air.  

Some other methods split oxygen atoms by exposing them to high-energy particles (like negative ions from ionizers) or UV-V rays (185 nm) and can also generate ozone.  

Ozone is also created as a product of various chemical reactions. For example, when nitrogen dioxide (NO2) reacts with other nitrogen oxides (NO) or poisonous chemicals, it can create ozone as a byproduct.  Nitrogen dioxide is a common product of burning fuel.

Side Effects

When produced artificially, ozone reacts with the biological molecules in our body and changes their chemical makeup, which can lead to various health complications. As an irritant, it can also cause many other side effects, such as: 

  • General symptoms: Nausea, vomiting, headache, skin and eye irritation 
  • Respiratory Distress: Ozone irritates the lungs and damages the epithelial lining. This results in difficulty breathing, wheezing, coughing, and sneezing.  
  • Asthma Attacks: Ozone makes lungs more susceptible to environmental triggers, so asthma and emphysema attacks might become more frequent after ozone exposure.  
  • Neurological Damage: Due to dyspnea (shortness of breath), the body’s oxygen levels drastically drop. This immediately affects the brain, manifesting confusion, hallucinations, and even irreversible loss of memory and cognitive functions. Prompt medical intervention is necessary to prevent permanent neurological damage. 
  • Heart Diseases: The lack of oxygen can induce necrotizing damage to vital organs like the heart. This may lead to myocardial infarction (MI) and pulmonary heart disease. Right-sided heart failure due to respiratory distress (cor pulmonale) is particularly common.  

Ozone can have a strong chemical-like odor, if your air conditioner is smelling like rotten eggs or sulfur then Plentiful Air has the cause and solution available here.

EPA Limits

As per the Environmental Protection Agency, 8 hours of exposure to 0.1 ppm of ozone is considered safe. However, beyond that level, the debilitating effects of ozone start showing, as the early signs of nausea, headache, wheezing, and chest pain progress to more severe symptoms.  

While the intensity of complications depends on the concentration and length of exposure, the signs may be more imminent in high-risk individuals. For example, pregnant women, children, the elderly, immunocompromised people, and patients with heart and respiratory disorders are more prone to ozone damage.  

Remember that ozone is a lethal gas, and an hour-long exposure to 50 ppm or more of ozone can prove fatal. 

Air Conditioners And Ozone Emission

Now that we know how ozone is produced, let’s talk about the general working of air conditioners to understand how they relate to ozone generation.  

How Air Conditioners Work

Here’s how an air conditioner typically works: 

  • A thermostat detects when the temperature falls below the preset level and starts the cooling process. 
  • First, a fan rotates to draw hot room air inside the unit (via return air ducts).  
  • Most modern air conditioners have filters that remove contaminants from the incoming air. While a generic dust filter (with large pores) is always used, advanced filtration systems may also include True HEPA filters (for microscopic particles and germs measuring up to 0.3 microns), activated charcoal filters (for gases and VOCs), electrostatic fiberglass (for particulate pollutants) or pleated media filters (sediment particles).  
  • Once inside the system, air encounters a cold evaporator coil. The refrigerant sealed inside the coil extracts heat from the air. 
  • While the blower fan emits cool air into the room, the refrigerant passes into the compressor, which is a part of the external AC unit. The compressor pressurizes the refrigerant, forcing it to release the heat energy outside through the vent. 
  • Lastly, the refrigerant returns to the evaporator coil to continue the cycle.  

Do Air Conditioners Create Ozone?

We know that ozone is produced by electrically splitting water molecules or producing free oxygen atoms by ionizing oxygen molecules. Since a typical air conditioner does not involve either of these processes, we can say that air conditioners do not generally produce ozone.  

However, air conditioners that come with built-in ionizers are an exception. Some ACs have integrated ionizers (such as LG 1.5 Ton Dual Inverter Premium AC, Haier HSU 19TCS3CN, etc.) that generate negative and positive ions.

These high-energy particles produce static electricity that charges the airborne particulate contaminants. This is a filtration mechanism as the charged particles fall on the ionizer and other surfaces and are thus, removed from the air stream.  

While the ionizers efficiently purify the air and reduce the energy consumption of the AC, the high-energy ions that they produce split oxygen molecules, producing free atoms, which then react with available oxygen to form ozone.  

Are Air Conditioners Bad For The Ozone Layer?

Air conditioners manufactured before 2010 contain hydrochlorofluorocarbon (HCFCs) and Freon and can severely damage the ozone. They have chlorine, which has a high ozone depletion potential (a single chlorine atom destroys over 100,000 ozone molecules).  

While air conditioning seems a harmless process, the truth is that the refrigerant they contain can deplete ozone.  

Ozone Depleting AC Refrigerants

The common ozone-depleting refrigerants used in air conditioners are: 

  • Freon: Also known as chlorofluorocarbons or HFCs, freon is one of the most effective refrigerants with a high affinity for heat. However, it has a high global warming and ozone depletion potential (GWP and ODP).  

They have a lifetime of about 50 to 500 years and, therefore, linger in the atmosphere. When sunlight interacts with a CFC molecule, it splits and releases chlorine.  

Chlorine breaks down ozone and acts as a catalyst to combine freed atoms to form oxygen molecules. The same chlorine molecule continues the destructive cycle with other ozone molecules as well.  

According to the Environment Protection Agency (EPA), a single chlorine atom can destroy over 100,000 ozone molecules.  

  • HCFC: Hydrochlorofluorocarbons or HCFCs are unstable and break down easily in the atmosphere. Therefore, they have low ODP (0.01 to 0.1) compared to CFCs. However, even in the brief lifetime of the compound, the destructive effects of chlorine on ozone are significant. 

Effects Of Ozone Depletion

We know that ozone protects against UV rays, especially UV-B rays (280-315 nm). Unfortunately, the use of Freon and HCFCs in air conditioners, dehumidifiers, refrigerators, and other domestic appliances has severely damaged ozone over the years.  

As a result, an alarming rise in eye cataracts, immune deficiency disorders, and non-melanoma skin cancers has been reported. 

Clean Air Act (CAA) and Ban On Freon and HCFCs

The Clean Air Act (CAA) is a Federal Law that regulates air emissions. In 1970, it authorized the US EPA to establish standards for protecting public health and the environment. These standards set by the EPA are called National Air Quality Standards (NAAQS). 

After ozone depletion and consequent health effects came to light, EPA has made laws to protect the sheath. Under the act, the ban on Freon and HCFC gradually came into effect. Starting from 1992 (for Freon) and 2001 (for HCFC), the two refrigerants started phasing out from the market, whereas their production was entirely banned in 2015 (for HCFC) and 2020 (for Freon). 

This explains why ACs manufactured before 2010 can potentially harm the ozone.  


R410A, also called Puron or hydrofluorocarbon (HFC), is a chlorine-free refrigerant with extremely zero ozone depletion potential (ODP). Since the ban on HCFCs and Freon, R410A has been used as their replacement in new air conditioners and other refrigerant-based appliances. 

Do Air Conditioners Pollute The Atmosphere?

Air conditioners use refrigerants with high global warming potential (GWP), emit greenhouse gases like CO2 and methane, and consume energy. Air conditioners, especially those manufactured prior to 2010, contribute to atmospheric pollution.  

Air conditioners contribute to global warming and are an environmental hazard: 

Global warming is a phenomenon in which carbon dioxide, methane, and other toxic airborne gases (usually created by combustion or burning of fossil fuels) reflect the heat emitted from the Earth’s surface back to the Earth, rather than letting it pass into the outer atmosphere and space.  

As a result, we notice an alarming increase in the planet’s temperature and other dangerous climate effects. 


The refrigerants used in air conditioners have extremely high global warming potential (GWP). For example, the greenhouse effect of a molecule of CFC is equivalent to 10,000 carbon dioxide molecules. Even the now-used HFC with zero ODP has 1000 times more GWP than carbon dioxide.   

Energy Waste

Air conditioners need high power to operate. This power is generated by burning fossil fuels and gases, and therefore, energy consumption is one of the largest sources of emission of greenhouse gases like CO2 and methane.  

Air conditioners have a “chimney effect,” i.e., they vent out heat but at the same time draw air inside the house for a cooling effect. This naturally increases the atmospheric temperature.  

How To Reduce Carbon Footprint Of ACs?

As of yet, we don’t have absolute solutions to make air conditioners environment friendly. However, considering the rising global warming, discussions on the subject are underway.  

After the phaseout of Freon and HCFC, the United Nations (UN) proposed a complete ban on hydrofluorocarbons (HFCs). It is suggested that the HFC ban can reduce global warming by 0.4 C

As per a 2016 report, around 150 countries have agreed to ban HFC. However, practical enforcement of the law is still due.  

Russell Singleton

Russell holds a Bachelor of Science (Environmental and Marine Geoscience) with Class I Honors. He is currently completing his doctorate in science and is passionate about all earth processes, especially isotope geochemistry and paleohydrology.

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