Does Ozone Kill Mold?
by Building Inspector and Indoor Air Specialist, Dan Schilling
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stay current with scientific research, 2) cite inaccurate and/or outdated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
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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