The Hazards of Ozone & Ozone Gas Generators InspectAPedia® -
Ozone Gas Exposure Hazards - A Summary of Ozone Hazards Indoors
The hazards of ozone generators in buildings
The effects of using ozone in buildings to "purify air" or to "kill mold"
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This article gives an overview of the hazards associated with use of ozone indoors as a "mold remedy" or as an "air purifier". Ozone is widely promoted by ozone generating equipment companies and cleaning services for use in indoor
building environments to deodorize, disinfect, "kill" mold, and for "general health".
Environmental testing experts and authorities such as the US EPA do not recommend use of ozone for mold "treatment". Furthermore, use of ozone indoors can be hazardous and can cause oxidation or other adverse reactions with other materials and chemicals indoors. Readers should also see Ozone Gas for additional discussion of how ozone can create problems in buildings.
OZONE HAZARDS - an Overview of the Hazards of Indoor Ozone Gas
Exposure to a level you can smell or exposure to ozone over long periods
at levels greater than 0.05 ppm for 24 hours at a time is likely to be dangerous: [2], [3] Health hazards to humans and animals occur and
can be severe at ozone levels used for indoor cleaning purposes.
At least some people
can smell levels of ozone down to 0.05 ppm. This odor-detection level is
already half-way to the recommended limit. If you are generating ozone indoors,
even at "low" levels a problem may be present. People become
desensitized to odors in a short time, perhaps 20 minutes. So if you do not
smell it, the ozone level could still be hazardous.
Problems associated with ozone gas exposure include:[4]
Lung irritation and infection.
Breathing pain, coughing, wheezing, difficulty when
exercising.
Permanent lung damage.
Aggravation of pre-existing asthma
Increased risk of lung illnesses such as bronchitis and pneumonia
Can I Use an Ozone Generator or Air Purifier to Get Rid of or Kill Toxic Mold Indoors?
Use of ozone to "remove" or "kill" mold is ineffective,
not recommended, and may be dangerous. Even if ozone were applied
at a concentration and for a duration sufficient to "kill" every mold spore in
a building (which is a very dubious claim), depending on the mold
genera/species present there is a good chance that the process leaves toxic and
allergenic particles in the building.
A "dead" (or non-viable) mold spore may
not grow but it can still be a health concern. The operative proper word for
mold remediation is "clean" or "remove", not "kill." In 1997,
Dr. Karin K. Foarde of Research Triangle
Institute, tested the ability of ozone to decontaminate fungi on
building materials. At ozone levels of 9 ppm for a 23-hour exposure, ozone was
found to be ineffective. [5] (Notice that this is 90-times higher than permitted ozone exposure. Exposure at
these "deodorizing" levels would be considered extremely toxic to humans.)
This
ozone treatment procedure is not recommended by the NY City Department of Health
Guidelines on the Assessment and Remediation of Fungi in Indoor Environments. Jim Holland's article on Ozone as a "mold remediation
step" is available online [6]and is a good summary of this point. Jack
E. Peterson's 1987 excellent work "Health Hazards of some Gases" also addresses
ozone hazards but it may be harder to find so I have quoted from it at the end
of this paper.
Deodorization and cleaning claims are questionable: The apparent deodorization at high ozone levels may
be simply the effect of a general desensitization to odors in the nose of
building occupants rather than actual removal of an odor source. Ozone has been
used following building fires to "reduce" smoke odors but even in this
application it does not remove soot.
Can I use Ozone or Ozone-Based Air Purifiers to Get Rid of Indoor Odors
The answer is, maybe.
If, for example, there is a
persistent odor source (such as a dead animal, flood damage, mold in building wall and ceiling cavities),
no amount of "air treatment" of any kind will remove the problem source. There
is no substitute for the actual physical effort to find and remove the offending
source. Cleaning or removing the problem source is proper and effective. Professional use of ozone, at concentrations and durations which the applicator guarantees
will not damage building materials or cause other outgassing, may be helpful as one step in a cleaning procedure where mold is not involved.
Ozone has been used
successfully in water treatment and in disinfection of cooling towers and
possibly wastewater. However it is not a durable, reliable treatment in that O3
molecules are highly reactive and volatile and thus treated substances do not
remain so.
Use of ozone may oxidize and damage materials and
increase odor levels:>[7] If ozone is no longer
being generated in a building the presence of ozone will diminish quite
rapidly. However, other odors may remain or may even be increased.
Under What Circumstances Can Use of Ozone Indoors Lead to More Odor Problems than Before?
Because ozone is a very powerful oxidant, it may react
with (oxidize) many materials found indoors, including carpets, carpet padding
(especially rubber), other floor coverings, furniture, furniture cushion foam,
and even surface paints and finishes. A common example is ozone-oxidized rubber
carpet backing or padding. We ather research and other studies indicate that any
material that will oxidize may be expected to react with ozone, especially
cross-linked organic molecules, especially rubber.
Use of ozone may produce dangerous airborne byproducts: In other words, attempts to use high levels of ozone
to "clean" or "deodorize" building interiors may in fact generate a second
generation of unpleasant and even dangerous outgassing which may remain,
persistent indoors, after the ozone "treatment." Examples include increased levels of indoor
formaldehyde, formic acid and other acid gases, toluene, or other toxic
chemicals.
Use of ozone may increase sub micron particulates: Attempts to use high levels of ozone to "clean" or
"deodorize" building interiors may also increase the level of extremely small
sub-micron particles which themselves can be severe respiratory irritants.
Results of some controlled studies show that concentrations of ozone considerably higher than these standards are possible even when a user follows the manufacturer’s operating instructions.
There are many brands and models of ozone generators on the market. They vary in the amount of ozone they can produce. In many circumstances, the use of an ozone generator may not result in ozone concentrations that exceed public health standards. But many factors affect the indoor concentration of ozone so that under some conditions ozone concentrations may exceed public health standards.
In one study (Shaughnessy and Oatman, 1991), a large ozone generator recommended by the manufacturer for spaces "up to 3,000 square feet," was placed in a 350 square foot room and run at a high setting. The ozone in the room quickly reached concentrations that were exceptionally high--0.50 to 0.80 ppm which is 5-10 times higher than public health limits.
In an EPA study, several different devices were placed in a home environment, in various rooms, with doors alternately opened and closed, and with the central ventilation system fan alternately turned on and off. The results showed that some ozone generators, when run at a high setting with interior doors closed, would frequently produce concentrations of 0.20 - 0.30 ppm. A powerful unit set on high with the interior doors opened achieved values of 0.12 to 0.20 ppm in adjacent rooms. When units were not run on high, and interior doors were open, concentrations generally did not exceed public health standards (US EPA, 1995).
The concentrations reported above were adjusted to exclude that portion of the ozone concentration brought in from the outdoors. Indoor concentrations of ozone brought in from outside are typically 0.01- 0.02 ppm, but could be as high as 0.03 - 0.05 ppm (Hayes, 1991; U.S. EPA, 1996b; Weschler et al., 1989, 1996; Zhang and Lioy; 1994). If the outdoor portion of ozone were included in the indoor concentrations reported above, the concentrations inside would have been correspondingly higher, increasing the risk of excessive ozone exposure.
None of the studies reported above involved the simultaneous use of more than one device. The simultaneous use of multiple devices increases the total ozone output and therefore greatly increases the risk of excessive ozone exposure.
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[6]Ozone
is not a substitute for mold removal and its reaction with building materials,
but applied by an expert may help deodorize, a cleaning article by Jim Holland -
http://www.icsmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,3035,118663,00.html
[7] Ozone as an oxidant, a few references from the Canadian Government
Bogaty,
H., Campbell K. S., and Appel, W. D. (1952). The oxidation of cellulose by ozone in small
concentrations. Text. Res. J. 22: 81-83.
Bradley,
C. E., and Haagen-Smit, A. J. (1951). The application of rubber in the
quantitative determination of ozone. Rubber Chem. Technol. 24: 750-755.
Cass, G. R., Nazaroff, W. W., Tiller, C., and Whitmore, P. M. (1991). Protection of
works of art from damage due to atmospheric ozone. Atmospheric Environment,
25A( 2): 441-451.
Druzik, J. R. (1985). Ozone: The Intractable Problem. We stern Association for Art
Conservation newsletter. Http://sul-server-2.stanford.edu/waac/wn/wn07/wn07-3/wn07-302.html
(vol.7, no. 3)
[8] "Health Hazards of some Gases" Jack E. Peterson, P.E., CIH, Ph.D., May, 1987
Ozone Gas Hazards Description in our article
"Effects of Toxic Gas Exposure to Ammonia, Arsine Arsenic Bromine Carbon Dioxide Carbon Monoxide Hydride Ozone & others"
A Toxic Gas Testing Plan: A Gas Sampling Plan for Residential and Commercial Buildings lists some of the toxic indoor gases for which we test, depending on the building complaint and building conditions
Gas Exposure Hazard Levels: for Toxic Gas Exposure to Ammonia, Arsine, Arsenic, Bromine, Carbon Dioxide, Carbon Monoxide, Hydride, Ozone - allowable exposure levels and hazard levels
Formaldehyde: US EPA. UFFI (Urea Formaldehyde Foam Insulation) was previously considered a hazard (formaldehyde outgassing).
Subsequent research virtually closed concern regarding this material; however formaldehyde appears to remain a health concern for sensitive individuals.
Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.
Sampling for gases in air such as VOC's, MVOC's, toxic chemicals, and combustion products.
Unfortunately no single test or tool can detect all possible building contaminants. We use methods and equipment which can test for common
contaminants. If the identity of a specific contaminant is known in advance we can also test for a very large number of specific contaminant
gases in buildings.
We use gas sampling equipment provided by the two most reliable companies
in the world, Draeger-Safety's detector-tubes and Drager accuro bellows pump, the Gastec cylinder pump
and detector-tube system produced by Gastec or Sensidyne, and
we also use Sensidyne's Gilian air pump. For broad screening for combustibles and a number of other
toxic gases and for leak tracing we also use Amprobe's Tif8850. All of these instruments, their applications, and sensitivities (minimum detectable limits) for specific
gases are described in our Gas Sampling Plan online document.
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