What is Ozone?

Ozone is a pale blue and highly reactive gas, present both naturally and through man-made activities in the earth’s atmosphere. It has a sharp smell like chlorine bleach. It’s also known as trioxygen, as it is an inorganic chemical compound composed of three oxygen atoms. Three oxygen atoms make one molecule of ozone and its chemical symbol is O3. Ozone is either harmful or useful based on where we can find it. Ozone has various uses as well as hidden dangers that we will get to know in this blog.

We can find ozone or O3 in the two layers of the atmosphere. The first is the Stratosphere level (upper atmosphere), and the second is the Troposphere level (lower atmosphere). The troposphere is the lowest level of the atmosphere in which humans live. The troposphere is present just below the stratosphere. We can ambient air ozone and indoor ozone at the ground level. We’ll get to know the causes, effects, uses, and hidden dangers of ozone down below.

The Greenhouse Effect

According to UCAR ( University Corporation for Atmospheric Research), about 3-7% of the Greenhouse Effect on Earth is due to ozone. It is also a greenhouse gas. Several gasses are responsible for the greenhouse effect including O3. Other gasses include carbon dioxide, water vapor, methane, and nitrous oxide. These molecules of these gasses have the property of trapping the heat very easily.  

This results in trapping the heat inside the earth’s lower atmosphere. According to NASA, the greenhouse effect is how heat is captured close to Earth’s surface by ‘greenhouse gasses.’ Nitrogen and oxygen comprise a large number of gases present in the atmosphere. They can not absorb heat and add to the greenhouse effect.

Types of Ozone and its Hidden Dangers

Depending upon the sources and where it is found, it can be classified into three categories,:-

1. Earth’s Upper Atmosphere: The “good” ozone

On the Stratospheric level, ozone exists in the form of a layer. This layer is formed due to the natural reaction between oxygen molecules and UV radiation from the sun. This is known as the “Ozone Layer.” Its thickness is about 300 Dobson units (3 millimeters). It is found approximately 30 miles above ground level. This layer helps save the living organisms on earth from harmful UV radiation. 

This layer acts like an umbrella that protects humans and other living things from the harmful effects of UV radiation. It absorbs 97%-99% of the radiation from the sun. It is better known for trapping harmful UV radiation from entering the earth’s surface. If this layer is absent, harmful UV radiation can penetrate the earth’s surface. This could harm living organisms, damage the human skin, and harm the DNA structure in plants and animals. As a result, their development, functioning, growth, and reproduction process will be at risk. In addition, the entire food chain will be affected. That is why it is called the “good” ozone. 

2. Earth’s Lower Atmosphere: The “bad” Ozone (or OUTDOOR/AMBIENT OZONE)

Ever wondered why Ozone is harmful in the troposphere? O3 on the lower level is a gas that does not have any direct emission sources. It is a secondary gas formed when heat and sunlight react with various chemicals present outdoors react with heat and sunlight. These include chemicals like Nitrogen oxide (NOx), Volatile Organic Compounds (VOCs), Heat, and Sunlight. This happens when emissions from vehicles, industries, power plants, chemical plants, refineries, and other sources react chemically with heat and sunlight. Volatile organic compounds and nitrous oxides are harmful and dangerous individually, and when these two combine with heat and sunlight, they turn into ground-level Ozone.


Smog is a by-product of ground-level ozone. It can trigger asthma, deteriorate bronchitis, and emphysema. Smog is a form of air pollution that reduces visibility on roads that leads to several road accidents. If the visibility is zero at a certain distance, that means that there is smog in the area. The levels of smog could be determined, depending on how far the visibility is. During bad pollution days, the road visibility is almost zero. So drive slowly when there is smog on the roads. Fine particles of air pollutants with a diameter of 2.5 microns or less are its main cause (PM2.5, Particulate Matter). These pollutants can enter deep into the lungs and then into the bloodstream. This can cause serious health effects like asthma, bronchitis, and lung and blood cancer. 

Why is ozone dangerous?

Inhaling ozone can be harmful to people with asthma, children, pregnant women, older adults, and people with certain genetic conditions. People with a lower intake of nutrients and outdoor workers fall under the same category. Such people are more susceptible to catching allergies because of their weaker lungs. These allergies can irritate your nose and throat in the short term and can lead to severe health issues in the long term. The groups of people mentioned above are more sensitive to ozone gas than healthy individuals. Ozone exposure can damage the lungs of a healthy person too. The healthy working organs of such individuals might also be compromised. The harmful gas can cause several problems for humans and the ecosystem.

Effects of ozone on human health

Ozone exposures in humans may:

  • Constrict the breathing airways and trap air which leads to shortness of breath.
  • Soreness in the throat
  • Cause chest pain while deep breathing
  • Make lungs vulnerable to diseases like asthma.
  • Aggravation of asthma
  • Increase in frequency of respiratory infections
  • Damage to the breathing tract.

Ozone and Ecosystem

If it is present at an abnormal level in the ambient air, it can harm various species of flora and fauna. These include vegetation, forests, wilderness, parks, and the ecosystem as a whole:

  • Change habitat quality
  • Alter water and nutrient cycles
  • Loss of species diversity (plants, animals, fish, and insects)
  • Alter specific assortments of plants present in forests

How and where is it used? 

Being a harmful gas, can ozone have other applications? Ozone is a powerful oxidant that is used in both industrial and consumer applications that are related to oxidation. Its applications are:

  • Water and air purification: it is a great oxidant, used in the purification of water and air to remove impurities as
  • Food processing and preservation: It is used to preserve certain foods and products and sanitize them. For instance, fresh fish, fresh fruits and vegetables, and eggs during cold storage.
  • Medicine: It is used in medical fields like surgery, ozone therapy, dental and optical care.
  • Surface treatment.
  • Aquaculture and fish farming: Ozone provides effective disinfection without producing harmful byproducts or chemical residuals that could harm aquatic animals.
  • Chlorine-free production of paper by bleaching the pulp.


Does Ozone only exist in the Stratosphere and outdoors?

The answer is no. We often thought that ozone only exists in the form of a layer in the Stratosphere and in the form of gas as an air pollutant in the ambient environment. Ozone can exist indoors as well. Only breathable ozone is harmful when it exists on the lower level of the atmosphere. Otherwise, it’s a very useful gas that protects us from UV radiation. It has various applications due to its chemical properties, like purification, sanitization, etc.

On the other hand, it is dangerous to human health if inhaled directly. We are not aware of the dangers of ozone exposure and its sources that can be present inside their homes. According to the US EPA, Inhaling ozone can cause coughing, shortness of breath, worse asthma or bronchitis symptoms, and irritation and damage to airways. High ozone exposures in short intervals can even result in disorders like lung cancer, bacterial pneumonia, pulmonary embolism, and possibly death. There is no doubt that ozone can kill you.

Indoor ozone sources:

Many unknown products and ozone emitters can cause indoor ozone. Many products and sources inside your homes may emit ozone as their derivative.

These sources include:-

  1. Laser printers and photocopiers: Ozone gas is generated from an electro-photographic process, while printing or photo-copying.
  2. Certain purifiers: Air purifiers are intended to work by altering harmful air pollutants. So, the air is purified and considered harmless. Certain air purifiers change the nature of air particles and produce ozone as their by-product.
  3. Facial steamers: Exposure to specific facial steamers that use ozone-emitting UV bulbs, may raise concerns for sensitive groups, like people with lung infections and ailments or people that use these products daily.
  4. Laundry water treatment appliances: Ozone reacts with organic compounds and oxidizes them, working as effectively as a detergent. But excessive usage of such products is not advised.
  5. Disinfectants: It is extremely effective as a germicide against bacteria and viruses. Indoor ozone emissions can be minimized by using alternate products.
  6. Automated vegetable washers: Ozone not only oxidizes the remaining chemical leftover from pesticides on the surface of fruits and vegetables but is harmful to humans too. It can harm your body in many ways, ranging from chest pains to lung and heart diseases and even death. 

What is indoor ozone and its hidden dangers?

Indoor air pollutants consist of many air pollutants like PM1, PM2.5, CO2, O3, etc. We need to eliminate these harmful air pollutants to breathe healthy and clean air. The purpose of cleaning the air is to minimize ozone and its hidden dangers indoors. Therefore, making sure people indoors breathe good air so life expectancy could increase. If the life expectancy of an individual increases, the same affects the global rate of healthy individuals with longer life expectancies. To eliminate hidden dangers from ozone and other pollutants, we need to:

Eliminating the ozone emitters-

Read the instruction manuals carefully before purchasing certain products. You should not use a product if it can potentially emit ozone. Start minimizing the usage of such products or look for second options. Make sure to use the products that do not emit ozone as their by-product. As products like photocopiers and printers emit ozone gas, try minimizing their usage. 

Proper ventilation

Use activated carbon filters to eliminate ozone from ventilated air, which absorbs ozone from the air passing through the HVAC system. If you do not live in a highly polluted area, air ventilation is extremely useful in reducing the levels of air pollutants indoors. Air ventilation also helps in getting fresh outdoor air into your home. (It is preferable only if pollutants like smoke, smog, dust, etc. are not contaminating the ambient air.)

If not, you can make sure to limit the ambient ozone by keeping the doors and windows closed on polluted days. This will make sure that ambient pollutants that are harmful, do not enter indoors.

Cleaning the air indoors

Air cleaning refers to removing impurities from the air that we breathe. Its main purpose is to prevent harmful particles and hidden dangers from ozone that are present in the air from penetrating our breathin