We are frequently asked about the effectiveness and appropriateness of using ozone generators during mold remediation. The potential benefit of resolving the toughest mold problems by simply plugging in a machine that “kills mold dead” sounds too good to be true – and it is! Plus it can be a serious health hazard.

While Ozone does have a number of useful applications in the emergency restoration services field (primarily in smoke odor control and VOC reduction), we strongly would caution against using it in regard to mold remediation. Studies do indicate high levels of ozone will have some level of killing bacteria on surfaces and to a lesser degree regarding mold. Ozone generators are pretty good at oxidizing things in the air where the particle density is far less than what one would find on a surface.

The question is what is left behind after Ozone oxidizes something? What remains after ozone “attacks” (for lack of a better word) a mold particle (a piece of mold structure or spore) in the air? Does it make the mold particle disappear completely? Does it change it into something that’s not harmful? It is this question that remains to be answered satisfactorily by any studies that we know of.

We’ve heard many claims by various products and substances over the years, but all of them are eventually exposed as over-stated or outright fraud. Plus there are numerous serious safety concerns with using high-levels of Ozone inside occupied buildings (and you would need to use very high levels to do anything to mold). These are summarized below in an excerpt from an EPA report.

Anyone who recommends using ozone on a mold remediation project is mis-applying information from ozone studies to a situation where Ozone is not an appropriate, or at least not the best, choice.

Fogging Concrobium Mold Control to reduce airborne particulates and apply a residual mold-resistant surface treatment for mold, by comparison is far safer and far less expensive than ozone… and is a far better option.

The United States Environmental Protection Agency has done considerable research on using ozone machines and has a few key conclusions;

Whether in its pure form or mixed with other chemicals, ozone can be harmful to health.

When inhaled, ozone can damage the lungs. Relatively low amounts of ozone can cause chest pain, coughing, shortness of breath and, throat irritation. It may also worsen chronic respiratory diseases such as asthma as well as compromise the ability of the body to fight respiratory infections.

Some studies show that ozone concentrations produced by ozone generators can exceed health standards even when one follows manufacturer’s instructions.

Many factors affect ozone concentrations including the amount of ozone produced by the machine(s), the size of the indoor space, the amount of material in the room with which ozone reacts, the outdoor ozone concentration, and the amount of ventilation. These factors make it difficult to control the ozone concentration in all circumstances.

Available scientific evidence shows that, at concentrations that do not exceed public health standards, ozone is generally ineffective in controlling indoor air pollution.

The concentration of ozone would have to greatly exceed health standards to be effective in removing most indoor air contaminants. In the process of reacting with chemicals indoors, ozone can produce other chemicals that themselves can be irritating and corrosive.

For full EPA report click HERE

Other resources:
OZONE GENERATORS AND INTERIOR MOLD REMEDIATION,  A Recipe for Disaster

Facts on Ozone use…Beware!