Ozone is a molecule composed of three oxygen atoms (O3) that exists naturally in the stratosphere, where it provides a protective shield against the sun’s ultraviolet radiation. However, when this gas is found at ground level, particularly indoors, it transitions from a protective layer to a harmful pollutant. Ground-level ozone is a highly reactive oxidant that poses a threat to respiratory health, making its presence in the home a significant air quality concern. Understanding how this pollutant enters and is generated within a residence is the first step toward mitigating exposure risks.
Primary Sources of Ozone Inside Your Home
Ozone enters the home environment through two primary pathways: infiltration from outdoor air and generation by indoor devices. The majority of indoor ozone originates outdoors, where it is a main component of photochemical smog. This ground-level ozone seeps into a home through open windows, doors, and general air leakage.
The more concerning sources are devices that intentionally or unintentionally produce the gas inside the living space. Electronic appliances that rely on high-voltage electricity can generate ozone as a byproduct, including older or high-volume office equipment like laser printers and photocopiers.
Specific types of air cleaning devices are the most significant indoor ozone generators. Products marketed as “ionic air cleaners,” electrostatic precipitators, or those that explicitly use ozone generation to “clean” the air can release harmful concentrations directly into the room. These purifiers should be avoided.
Health Risks of Indoor Ozone Exposure
Exposure to ozone can have immediate and long-term negative effects on the respiratory system. As a powerful oxidant, inhaling it causes inflammation and irritation in the airways and lungs. This irritation can lead to uncomfortable symptoms like coughing, a sore throat, and chest pain.
The gas causes the muscles in the airways to constrict, which traps air within the tiny air sacs of the lungs called alveoli. This can result in shortness of breath and wheezing, even in otherwise healthy individuals. For those with pre-existing respiratory conditions, such as asthma, bronchitis, or emphysema, exposure to ozone can severely aggravate symptoms and increase the frequency of attacks.
Vulnerable populations, including young children, the elderly, and people with existing respiratory or cardiovascular diseases, face a greater risk from ozone exposure. Research also suggests that ozone exposure can negatively affect cardiovascular function by disturbing metabolic processes.
Practical Steps to Reduce Ozone Levels
Eliminating Indoor Sources
The most direct and effective action to reduce indoor ozone is eliminating the sources that are actively generating the gas. Homeowners should immediately stop using any air purifiers, humidifiers, or ionizers that are known to produce ozone. When purchasing air cleaning technology, it is wise to look for products certified by the California Air Resources Board (CARB).
CARB certification requires that air cleaning devices demonstrate ozone emissions do not exceed 0.050 parts per million (50 ppb), a limit designed to ensure safety. Devices using only mechanical filtration, such as HEPA filters, typically do not generate ozone and are a safer choice. Electronic air cleaners, including those with UV light components, must meet this strict ozone emissions standard to be certified.
Using Specialized Filtration
Proper filtration is a necessary strategy, but it requires the right technology, since standard HEPA filters are designed to capture particulate matter and do not remove gaseous ozone. To chemically neutralize the ozone molecule, air purifiers must incorporate filters containing a sorbent material, most commonly activated carbon. The activated carbon works by adsorbing the ozone gas or by reacting with it, effectively destroying the pollutant as air passes through.
These specialized filters should be regularly maintained and replaced according to the manufacturer’s schedule to ensure their ozone-removing capacity remains high. Using a high-quality filter within a central Heating, Ventilation, and Air Conditioning (HVAC) system can also help treat the air distributed throughout the home.
Managing Ventilation
Increasing ventilation can also help by diluting indoor pollutants, but this step requires careful timing due to outdoor ozone infiltration. When local air quality reports indicate low outdoor ozone levels, opening windows and using exhaust fans in the kitchen and bathroom can effectively introduce fresh air and remove stale air. Exhaust fans should be used when operating ozone-generating appliances to vent the gas directly outdoors.
Conversely, during periods of high outdoor smog or air quality alerts, windows and doors should be kept closed to limit the influx of ozone. During these times, relying on a closed-system HVAC unit equipped with an activated carbon filter is the best approach to continue circulating clean air without drawing in the high concentrations of outdoor ozone.