Ozone, a molecule composed of three oxygen atoms (\(\text{O}_3\)), exists naturally in the Earth’s atmosphere. This unstable gas acts as an extremely powerful oxidizing agent, meaning it readily reacts with and breaks down many other substances upon contact. Because of this high reactivity, ozone has long been employed in industrial and commercial settings for its ability to neutralize contaminants. The potential of this strong oxidant to eliminate microscopic threats, specifically viruses, has led to significant interest regarding its practical use as a disinfectant.
How Ozone Inactivates Viruses
Ozone’s effectiveness against viral particles stems directly from its nature as a powerful oxidant, which allows it to chemically destroy the physical structures viruses rely on for survival and infection. This chemical attack is known as oxidation, and its target depends on the specific viral architecture.
Enveloped viruses, such as influenza and coronaviruses, are particularly susceptible to ozone because they possess a fragile outer layer made of lipids, or fats. Ozone quickly reacts with the unsaturated fatty acids in this lipid envelope, causing peroxidation that destabilizes and ultimately ruptures the protective coating. The loss of this envelope prevents the virus from successfully binding to and entering host cells, rendering it non-infectious.
Even non-enveloped viruses, which lack the fatty outer layer and are generally more resistant, are vulnerable to ozone’s oxidative power. Ozone attacks the viral capsid, the protein shell that encases the genetic material. This action also extends to the internal components, where ozone can degrade the nucleic acids (RNA or DNA) that constitute the viral genome. By damaging the structural proteins and the genetic instructions, ozone ensures the virus cannot replicate.
Practical Applications of Ozone Disinfection
The ability of ozone to inactivate viruses is leveraged in large-scale, controlled environments where human exposure can be entirely eliminated. One of the longest-standing applications is in municipal and bottled water treatment, where ozone is used as a potent disinfectant. In this context, ozone dissolved in water, known as aqueous ozone, rapidly neutralizes pathogens, including viruses, without leaving behind harmful chemical residues, as it naturally reverts to oxygen.
Ozone gas is also utilized for air and surface disinfection, particularly in industrial or healthcare settings, though strict protocols are followed. It is used to sanitize equipment or entire rooms, such as hospital wards or production facilities, only when they are completely unoccupied. The gaseous nature of ozone allows it to penetrate intricate spaces and surfaces that conventional liquid disinfectants might miss, making it useful in controlled fumigation of HVAC systems.
The application is highly regulated, requiring specific concentrations and contact times to ensure a thorough kill, followed by a mandatory aeration phase to remove the residual gas. These controlled applications involve high concentrations of ozone, many times greater than what is safe to breathe. This reliance on high-concentration treatment in sealed, empty spaces ensures the gas’s virucidal power is utilized while mitigating severe safety risks to personnel.
Health Risks and Safety Concerns
Despite its efficacy as a disinfectant, ozone is a severe respiratory hazard, and its use outside of controlled industrial environments poses significant health risks to people and animals. The same powerful oxidizing property that destroys viruses also damages the tissues of the respiratory system. Inhaling ozone can cause inflammation and irritation in the airways, leading to immediate symptoms like coughing, throat scratchiness, and chest pain.
Exposure can also reduce lung function, making it difficult to breathe deeply and aggravating pre-existing conditions like asthma. Children, the elderly, and individuals with chronic respiratory diseases are particularly vulnerable to the harmful effects of ozone, even at relatively low concentrations. Long-term or repeated exposure to elevated ozone levels can be associated with a greater decline in lung function and the progression of diseases like emphysema.
The concentrations required to effectively kill viruses, especially on surfaces or in the air, are far above the levels considered safe for human or animal respiration. For this reason, regulatory bodies, including the Environmental Protection Agency (EPA), do not certify or recommend the use of ozone generators for air purification in occupied residential spaces. Consumers should avoid using these devices in their homes while people or pets are present, as the ozone levels needed for effective viral inactivation are toxic and can cause serious, long-term harm to the lungs.