Park yourself in just about any online mold forum, social media group, or chat and you will see a lot of support for the use of ozone to kill mold. Does ozone kill mold? Is it safe to use? Let’s dive into what is a very controversial and loaded topic. I will do my best to keep it simple by breaking this post into digestible parts.
What is Ozone?
Ozone is the principal element of the ozone layer, which traps the sun’s heat and is essential to life on Earth. Unlike breathable, stable oxygen molecules, which are composed of two oxygen atoms, ozone is composed of three. The third oxygen atom in ozone can easily detach from the ozone molecule and reattach to other substances, altering their chemistry.
What Produces Ozone?
In order to use ozone to kill mold, you must start with an ozone generator. Ozone generators intentionally produce the toxic gas ozone and are sold as air cleaners for commercial and residential applications. Specifically, they are advertised to deodorize, disinfect, kill or remove dangerous or irritating airborne particles in indoor environments including mold.
How Do Ozone Generators Make Ozone To Kill Mold?
Ozone generators produce the gas in large enough quantities that unstable organic compounds will react with the gas and, supposedly, be altered so that they will no longer be irritating or dangerous. Since ozone is composed of three oxygen molecules, it can combine itself with things like mold and mold spores. It will change them in such ways that it kills the spores and cells that compose the mold.
In more scientific terms, ozone generators make ozone by breaking apart oxygen molecules, a process that can be accomplished in the following ways:
Silent Corona Discharge
All electrical discharges, such as lightning, produce ozone by splitting normal oxygen and creating single oxygen atoms, which then attach themselves to O2 to form ozone (O3). Silent corona discharge-ozone generators operate by this principle.
This process is similar to the formation of ozone in the upper atmosphere, where the sun’s ultraviolet radiation causes O2 to split into individual oxygen atoms. This method is generally regarded as less efficient than corona discharge.
Does Ozone Kill Mold?
Yes, technically ozone kills mold. But there are a LOT of limitations.
Ozone does not penetrate walls, floors, or other surfaces. While it can get into nooks and crannies, ozone can only tackle air born mold and surface mold. Ozone can only go where air can go. As I am sure you are aware, mold is never just in the air.
Ozone will not remove the mold spores it just rendered inactive nor will it kill the mold spores that are growing deep down into building materials and household items. Mold remediation including properly removing the moldy materials and items still needs to be completed.
Using ozone to kill mold does not correct the conditions that allowed the mold to grow in the first place. You have to fix the leak or address the cause of moisture intrusion before you begin dealing with the resulting mold.
In fact, using ozone to kill mold is pointless if you haven’t addressed the root cause and removed all the moldy building materials and household items. As soon as you disturb the mold, spores will go flying and you will recontaminate your home or the contained area.
Ozone typically isn’t used before remediation. There are two exceptions however.
- If you can’t address the mold problem right away, ozone will halt mold growth for a very short period of time.
- Ozone works well as an antimicrobial treatment prior to disturbing mold during remediation. This helps to prevent any inadvertently transported spores from being able to reproduce in other areas by deeming them nonviable (dead). This is typically only done when the area being remediated can’t be effectively contained or is in an area of the building where access requires a lot of movement through other parts of the building.
But wait – before you start thinking that ozone treatments are a good idea… consider this.
The amount of ozone it takes to truly kill mold is so toxic it will kill you too. Therefore, you would need to stay out of your home for several days if not a week after treatment.
This also means that the vast majority of ozone generators available for sale or to rent to the general public are NOT powerful enough to produce the amount of ozone needed to effectively kill mold.
In addition, ozone treatments for mold need to be done in an airtight environment. This means that your house would need to be completely sealed up. No gaps around exterior doors or windows, all attic vents sealed, cracks and crevices closed up, etc… Most homeowners and remediation companies won’t go through all this effort. And effort it is.
Does ozone kill mold occurring to the EPA?
This is straight from the EPA’s website.
Available scientific evidence shows that at concentrations that do not exceed public health standards, ozone has little potential to remove indoor air contaminants. Some manufacturers or vendors suggest that ozone will render almost every chemical contaminant harmless by producing a chemical reaction whose only by-products are carbon dioxide, oxygen and water. This is misleading. The EPA does not certify or endorse any air cleaning devices or recommend air cleaning devices or manufacturers.”
Health Considerations When Using Ozone To Kill Mold
Unfortunately, the same chemical properties that allow ozone to alter organic material in household air also give it the ability to react with organic material inside the human body. Ozone’s chemical reactivity does not stop when it enters the body. It continues to release the extra oxygen atom, which damages cells. This released oxygen atom is an oxidizer, the opposite of an anti-oxidant that we might take to improve health.
These well documented scientific and medical facts form the basis for a number of health risks related to ozone. Four different government agencies have restrictions on ozone exposure, including the Food and Drug Administration (FDA), the Occupational Safety and Health Administration (OSHA), the National Institute of Occupational Safety and Health (NIOSH), and the Environment Protection Agency (EPA).
These agencies agree that low levels of ozone exposure can cause the following conditions:
- Chest pain
- Shortness of breath
- Throat irritation
- Worsened chronic respiratory diseases such as asthma
- Increased risk of developing bronchitis or pneumonia
- Compromised ability of the body to fight respiratory infections
There are a lot of other known health risks associated with ozone exposure but the above list are the most concerning.
The EPA notes that it is increasingly difficult to determine the actual concentration of ozone produced by an ozone generator because so many different factors come into play. Concentrations will be higher if more powerful devices are used in smaller spaces. Whether or not the interior doors are closed rather than open will affect concentrations as well. Additional factors which affect concentration levels include how many materials and furnishings are in the room to react with ozone, the level of outdoor air ventilation, and the proximity of a person to the ozone generating device. This means that you don’t really know how much ozone is left lingering in your indoor air.
It is VERY important to note that ozone can dull the olfactory sense, a fact that has led many experts to believe that ozone’s deodorizing abilities are at least partially due to an altered odor perception, rather than any change in the environment. So this means that just because you can’t smell mold doesn’t mean you have really removed mold.
Potential Damage To Items In A Home From Using Ozone To Kill Mold
Did you know that using ozone to kill mold can actually CREATE horrible odors? Yes, ozone is touted as a magic cure for odors but in fact, it can actually create new, nasty, toxic odors.
Basically if you are using ozone for mold then you likely are going to cause materials to oxidize. Here are some examples of materials that are known to give off obnoxious smells after misuse of an ozone generator. And by misuse I mean running an ozone generator too long and/or at too high a setting in too small a space.
- Carpet padding
- Foam anything
- Most cushions
- Items that have been painted or stained
- Electrical wire coatings
- Fabrics and art containing certain dyes or pigments
In addition to these materials giving off a horrible (irreversible odor), ozone is known to damage these materials to the point of rendering them useless.
Ozone generators can also damage plants in indoor environments. High levels of ozone will inhibit the ability of plants to open the microscopic pores on their foliage and breathe. Specifically, ozone can cause the following conditions in plants:
- Chlorosis, a condition in which the plant cannot produce sufficient chlorophyll to manufacture carbohydrates
- Necrosis which may lead to the death of the plant as a whole;
- Flecks or small irregular spots
- Small, darkly pigmented areas
Other Risks Of Using Ozone To Kill Mold
People’s susceptibility to ozone varies widely. An ozone generator should never be operated in occupied spaces, and the area should be adequately vented before people or animals are allowed to re-enter.
According to a report produced by the EPA, ozone generators are ineffective at reducing levels of formaldehyde and carbon monoxide, despite claims by manufacturers. Also, from the toxins with which ozone does react, there is a potential for the creation of new, potentially more dangerous toxins. For example, ozone mixed with chemicals from new carpet can create aldehydes, which can irritate the lungs. Other reactions may create formic acid, another irritant. The potential for chemical reactions in the average house is difficult to predict.
So Ozone Isn’t The Safest Or The Best Way To Kill Mold. What Is The Alternative?
The following alternatives can be used to deal with an indoor mold situation:
- Professional remediation for larger mold problems
- Removing moldy items and moldy building materials in a properly contained area and cleaning the area with EC3 products or Endurance Bio Barrier Cleaner Prep
- DIY mold removal for shower mold, toilet mold, and other bathroom mold
- DIY washing machine mold removal
- Fogging to remove air born mold
If you have outdoor mold, please visit my post about how to remove and prevent outdoor mold for more information on how to tackle that.
Notable references include:
- Portions of this article were used with permission from this original article.
Photo Credit – Ozone Graffiti: https://www.flickr.com/photos/duncan/4630974367/