What is ozone?

Ozone is a gas made of three oxygen atoms bound together. It is a reactive gas, having a tendency to give away one oxygen atom to other molecules. When it reacts with other molecules, it can make them unstable and cause them to degrade. It is not effective at removing particles like pet dander or pollen, but by reacting with molecules that our noses can detect it can remove room odors. Some manufacturers use this property of ozone to claim that it purifies the air.

How can ozone harm human health?

When we breathe in ozone, it can react with molecules in the lining of our respiratory systems in the same way it reacts with other substances in the air. Ozone is a respiratory irritant, and can cause throat irritation, coughing, shortness of breath, and chest pain.  People with asthma may have asthma attacks when exposed to ozone. In addition to the health risks of ozone itself, when ozone reacts with molecules in the air they can break down to make other molecules that are themselves respiratory irritants.

Where is ozone found?

Ozone is found high in the atmosphere in the ozone layer, where it is beneficial to human health by absorbing solar ultraviolet radiation. However, it is harmful to human health when it is found at ground level in air in cities, where it is generated when sunlight reacts with air pollutants. Ozone is the major component of smog and contributes to lowered air quality and increases in respiratory health problems.

Are air purifiers that produce ozone safe?

Air cleaners that produce ozone are not recommended because ozone levels cannot be carefully controlled. City air can have high levels of ozone, and this can result in levels of ozone high enough to cause health effects when combined with ozone-generating air cleaners. Use of ozone-generating air cleaners in a room that is smaller than the machine is designed for can lead to high levels of ozone. If a building does not have good air circulation, ozone can build up in the air.

What alternatives are there to ozone-generating air cleaners?

Air purifiers that do not generate ozone but filter air through a high efficiency particulate air (HEPA) filter are effective at removing particles from the air without adding potentially harmful ozone. HEPA filters do not remove odors, but many HEPA air purifiers also use an activated carbon filter that will remove odors. These purifiers work by removing contaminants from the air and do not add any harmful gases to room air.

Where can I get more information about ozone?


Updated 2023