What Is the Latest on the Use of Ozone to Decontaminate Moldy Buildings?
By Dr. Harriet Burge, EMLab P&K's Director of Aerobiology
I know this is an ongoing question, and there are remediators who are recommending ozone for
cleanup. However, although ozone can damage some fungi, there is not a single study in the
peer-reviewed literature that documents sufficient deactivation of fungi to be useful in
Most of the studies of ozone are found in the food industry. Ozone is effective in slowing the
growth of fungi on fruits and vegetables. However, under these circumstances, slowing growth for
even a few days is considered significant. Delays in spore production as long as 5 days have
been reported. While significant in the life of a vegetable, this delay is useless for a residence.
It is true that very high levels of ozone over several hours will significantly lower the
concentrations of culturable fungi on hard surfaces. At these concentrations, however, the ozone
will damage building contents. Also, ozone disappears rapidly from the air. It attaches onto
surfaces, including valuable ones that could be damaged.
Data from studies that assess fungi on materials in houses have not been impressive. Fifty
percent reductions have been achieved, and considered significant. However, reducing fungal
concentrations on a surface from 50,000 to 20,000, although it may be statistically significant,
is not important in a remediation sense. Also reported is the fact that fungi are more readily
damaged by ozone on smooth, hard surfaces than on porous surfaces.
Unfortunately, fungal growth is most likely on porous materials (such as wallboard) from which
it is difficult to remove, while a simple wipe with a damp cloth will remove fungi from smooth
Remember also that dead fungi may cause as many problems as living ones. It is far more effective
to not worry about whether or not the fungi are alive, but instead concentrate on fixing the water
problem and removing materials with fungal growth.
Overall, then, given the potential dangers of ozone damaging building contents and the possibility
of negative health effects both for remediators and for occupants, I would not recommend it's use.
In fact, given the negative literature, I would suggest that the use of ozone is contraindicated
in mold remediation situations.
This article originally appeared in the December 2010 issue of Indoor Environment Connections.
Reprinted by permission.
About Dr. Harriet Burge
Dr. Harriet Burge is EMlab P&K's Director of Aerobiology and Chair of EMLab P&K's
Scientific Advisory Board. Widely considered the leading expert in indoor air quality (IAQ),
Dr. Burge pioneered the field more than 30 years ago. She has served as a member of three
National Academy of Sciences committees for IAQ, including as Vice-Chair of the Committee
on the Health Effects of Indoor Allergens. View Dr. Burge's Curriculum Vitae.
Read "Ask Dr. Burge" articles