Does Ozone Kill Mold?
by Building Inspector and Indoor Air Specialist, Dan Schilling
© Copyright 2002 Residential Inspections LLC, All Rights Reserved
Today, there are still some indoor air quality professionals that wrongly believe ozone does not kill mold. Their error lies in that they 1) do not stay current with scientific research, 2) cite inaccurate and/or outdated information, 3) have never used ozone to kill mold, 4) allude to law suits against manufacturers of ozone producing devices without mentioning the positive outcomes of those lawsuits, and 5) lack understanding regarding the various levels of gaseous ozone and their relationship to efficacy.
There are also those who believe ozone is in fact, an effective antimicrobial. These include scientists who research ozone, the manufacturers of ozone producing devices currently used to kill mold, companies that use ozone as part of their mold remediation procedure, and the Federal Food and Drug Administration who has approved ozone as an antimicrobial agent. The following is quoted directly from the FDA rule (21 CFR part 173) which became effective June 26, 2001:
“SUMMARY: The Food and Drug Administration (FDA) is amending the food additive regulations to provide for the safe use of ozone in gaseous and aqueous phases as an antimicrobial agent on food”
The logical question would be, “if ozone is not an effective antimicrobial, why can it be used on the very food we eat”? Of course any thoughtful person would have to admit they have no answer for this question.
The University of New Hampshire and many other laboratories have done extensive research regarding the ability of ozone to kill both mold and bacterium.
Science has certainly proven that ozone kills both mold and bacteria, but to be fair, further elaboration is needed. The natural level of ozone present in our air outdoors (.03-.04ppm) is necessary for the health and well being of every living thing on the planet, and is the primary reason we go “out” for fresh air. These are the same levels reestablished by residential air purifiers to help maintain clean indoor air. However, these low levels are only partially effective as an antimicrobial and must be maintained continuously for this benefit. When ozone is used to effectively kill mold indoors, levels approximately 10 times higher are used. These higher levels are used only for short periods of time, in temporarily unoccupied spaces. Homeowners and mold remediators are now finding this method both expedient and practical for specific situations.
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). Ozone is also an excellent finishing treatment after a mold remediation project. Due to the fact that mold spores are microscopic, it is given that some spores will remain in the area after remediation and will likely be in areas that are difficult to mechanically clean. Because ozone uses air as the vehicle to find mold, it can treat any difficult area that airborne spores have traveled to: air ducts, air conditioner A-coils, attics, wall cavities, and crawl spaces.
It is important to understand that while ozone kills mold, it does not “clean” mold. Depending on the location of the mold, killing the mold may only be a partial solution. When touched or inhaled, mold can remain allergenic, pathogenic, or toxigenic, even after being rendered nonviable. Therefore, consideration needs to be given to the location of the contamination, and possibly the type of mold present. Whenever mold is discovered inside a building's heated envelope, whether viable or nonviable, it should be cleaned or otherwise removed if at all possible.
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