Ozone, a gas molecule composed of three oxygen atoms (\(\text{O}_3\)), occurs naturally in the Earth’s atmosphere, forming the protective ozone layer. At ground level, however, it is a highly reactive chemical with powerful oxidizing properties. This nature has led to its proposed use as a strong disinfectant for indoor air and surfaces, particularly during the recent pandemic. The question of whether this gas can effectively eliminate the SARS-CoV-2 virus, the cause of COVID-19, involves balancing scientific capability and health safety.
How Ozone Functions as a Disinfectant
Ozone is considered a broad-spectrum antimicrobial agent because it is a highly reactive oxidant. The third oxygen atom in the \(\text{O}_3\) molecule readily detaches to oxidize or “burn” other molecules it encounters. This strong oxidizing property makes it an effective tool against a variety of pathogens, including bacteria, fungi, and viruses.
When ozone contacts a virus, its primary action is attacking the exterior structure. For an enveloped virus like SARS-CoV-2, ozone disrupts the outer lipid membrane and the protein spikes used for host cell attachment. This damage compromises the virus’s structural integrity and its ability to infect living cells. If the outer barrier is breached, the oxidation can reach the viral genetic material, such as RNA, rendering it incapable of replication.
Scientific Evidence Against SARS-CoV-2
Laboratory studies have confirmed that ozone gas can inactivate the SARS-CoV-2 virus, but the necessary conditions are extreme and difficult to achieve safely in a real-world setting. To achieve high viral kill rates, researchers must apply high concentrations of ozone for specific periods. For example, one study found that 4,000 parts per million (ppm) for just two minutes was needed to fully inactivate the virus on contaminated face masks.
Another study demonstrated a 99.99% reduction of the virus, but it required high concentrations over a prolonged time, such as 55 minutes. Even lower concentrations that still show effectiveness, such as 4 ppm, required up to two hours to sanitize materials like fleece. These effective concentrations are far beyond what is considered safe for humans, creating a disconnect between laboratory efficacy and practical application.
Health Risks of Ozone Exposure
The same powerful oxidizing property that makes ozone an effective disinfectant also makes it a serious threat to human health. Ozone is a potent lung and respiratory irritant, even at relatively low concentrations. Inhaling the gas can trigger symptoms including coughing, shortness of breath, and irritation in the throat and chest.
Ozone exposure causes inflammation in the tissues that line the airways, which reduces lung function. People with pre-existing respiratory conditions, such as asthma, emphysema, or Chronic Obstructive Pulmonary Disease (COPD), are particularly vulnerable. Ozone can significantly aggravate their symptoms and increase the risk of infection. Long-term or repeated exposure can lead to permanent injury to the lungs, making ozone a regulated air pollutant.
Official Recommendations and Regulatory Status
Major health and environmental organizations advise against using ozone-generating devices indoors for air purification or disinfection. The Environmental Protection Agency (EPA) warns the public not to use ozone generators in occupied spaces. The consensus is that when ozone is used at concentrations within public health standards, it is not effective at removing viruses, bacteria, or mold from the air.
The level of ozone necessary for effective disinfection is unsafe for human exposure, creating an impossible dilemma for residential use. Furthermore, the EPA does not test or regulate ozone-generating devices as disinfectants, meaning that manufacturers’ claims about efficacy are not verified by the agency. Official guidance is to rely on proven methods like ventilation, filtration, and EPA-registered chemical disinfectants for managing air and surface contamination.