Ozone Toxicity & Ozone Gas Exposure Hazards InspectAPedia® -
The toxicity of ozone gas in buildings and ozone gas exposure limits
The effects of using ozone in buildings to "purify air" or to "kill mold"
The hazards of ozone generators in buildings
Questions & answers about the toxicity of ozone gas in buildings or other enclosed spaces
Toxicity of ozone gas: this article discusses Ozone Toxicity in Buildings - A Summary of Hazards of Indoor Ozone, Ozone Generators, and Use of Ozone for Mold Remediation.
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While there are some important uses of ozone (such as for medical disinfection under controlled conditions),
in general this is an idea which ranges from bad to dangerous in the home.
This article explains the effects of using ozone in buildings for these purposes
and warns consumers about misapplication of and health risks from ozone in buildings.
Because at least some of these claims are based on marketing desire, not good science, and
because ozone exposure can be both dangerous and ineffective indoors, I have
collected some information and references on this topic.
OZONE TOXICITY: - How toxic is ozone, general background, levels of ozone gas toxicity, ozone gas applications
Question: Is an indoor ozone generator harmful to family or pets?
A friend of ours gave us a ozone junior to use in our home it comes on for 10 minutes off for 10 minutes. We are happy with it as far as taking care of the pet odors or any odors but are concerned on whether it is safe to use as it had no paper work. I would just like to know whether this can be harmful to my family or pets? - N.A.
Reply: It depends ...
It might be. A competent onsite inspection or testing by an expert might find other unsafe conditions in your home or conditions that are affecting how your ozone air machine performs. That said, here are some things to consider:
Start by making sure you are using the equipment according to the manufacturer's instructions.
Beginning just below, we discuss actual ozone gas toxicity - harmful levels. Also see OZONE MSDS.
Also you can read about the actual STANDARDS FOR OZONE EXPOSURE but without expert testing in your own home you may have no idea how your home's ozone level compares with the standards.
Our opinion is that as a very crude rule of thumb, if you smell ozone or the air has a funny "electric" smell, that is if there is a detectable ozone odor, the equipment is probably not operating safely or correctly.
Other than that crude measure, you'd have to either rely on the manufacture's quality control and on following the product instructions, or you'd need to make actual ozone level measurements in the building where the equipment is used. We measure ozone gas levels (when we are convinced there is a reason to do so) using a gas measurement pump and tube system such as that described at Use of a Drager pump.
Properties and Actual Ozone Output of the OZN-jr ozone generator
Information about your "ozone junior" ozone generator: IF you are referring to the OZN-jr Ozone Generator that we noted is for sale at Amazon.com. An Amazon advertisement viewed in March 2011 indicated that the OZN-jr ozone generator unit produces 200 mg of ozone per hour. The advertising material asserts that the product is "good for deodorizing up to 1000 cubic feet." The product manufacturer, Sunlight Solutions, indicates that "Ozone output is 8 mg/hr."
How big is a 1000 cubic foot room? Figuring an 8-foot ceiling, that's about 125 square feet, or a 10 x 12 room.
Calculating ozone generator output concentration in a room: How much is 200 mg of ozone per hour seen in the [March 2011] Amazon Ad? We don't know because the 200 mg number looks incomplete. If that 200 mg of ozone is being produced over an hour in a 1000 cubic foot room, that would be a very low concentration of ozone. 1000 cubic feet = 23,317 liters. 200 mg of something distributed into 23,317 liters amounts to about 0.0085 mg per liter or about 0.0085 ppm. In other words, almost nothing.
How much is 8 mg/hour ozone output seen at the OZN-jr product web page [March 2011]? Following the calculation above, output is 0.0003 ppm - almost less than nothing.
In our OPINION, at those ozone output levels your machine would not be hurting anyone, but it also would not be doing much that you'll notice either. Our detailed text below states that " ... the odor of ozone can be detected and identified by most people at a concentration of from 0.02 to 0.05 ppm (parts ozone per million parts air + ozone)."
Watch out: there is a very wide range of ozone output from different types of ozone generating equipment, and some equipment can be used at output settings or in enclosed environments to produce levels of ozone gas dangerous to occupants and damaging to building contents.
What is the Legal Definition of "Up To" in Advertising Claims
With an advertising attorney we recently discussed the legal requirements for advertisers who make "up to" claims. She informs us that in the U.S. law on "up to" claims requires that the product meet the "up to" claim at least ten percent of the time. Translating this into plain language, in a given installation the OZN-jr can meet its advertising claims if in ten percent of cases it deodorizes 1000 cubic feet (that's a room that is about 8 feet by 15.6 feet or 125 square feet if the ceiling height is also 8 feet). And 90 percent of the time it can perform less well, or even not at all.
The ability to deodorize a space using just about any deodorizing method (other than complete removal of the odor source) depends on other variables that are certainly not under the product manufacturer's control, such as the level of odor or smell in the first place, the persistence and nature of the odor source, building air movement properties, space size, equipment location, and lots more.
"Ozone
is a kind (called an "allotrope") of oxygen . It is formed in the
ionosphere by the action of ultraviolet radiation from sunlight on oxygen.
Lightning strokes are another natural source of ozone and the characteristic
odor of that material can often be noted during and after a thunderstorm.
When
pollutants are emitted into the air either by man or nature, almost all are
eventually removed by one or more of several processes including reaction under
the influence of ultraviolet radiation. One series of such reactions results in
the formation of ozone as a "secondary" (formed by reaction in the
air) air pollutant, often in rather high concentrations (several tenths of a
part per million).
"As
ozone can be formed by nature's sparks (lightning), it can also be formed by
man's. Whenever an electrical spark or corona occurs in air, some ozone is
formed. This accounts for the characteristic odor noted near an operating
electric motor such as an electric shaver.
"Because
ozone is found in so many places, its toxicity (ability to injure a living
organism by other than mechanical means) has been investigated extensively
since the early 1900s. Experimentation has shown that the odor of ozone can be
detected and identified by most people at a concentration of from 0.02 to 0.05
ppm (parts ozone per million parts air + ozone). As the concentration increases
to a few tenths of a part per million, the first effect noted is likely to be a
feeling of dryness in the back of the throat. If a concentration on the order
of 0.2 or 0.3 ppm is inhaled more or less continuously for several hours to a
few days some lung irritation may result.
"Higher
concentrations can produce several kinds of toxic effects if exposures are
sufficiently prolonged. Eye irritation (despite newspaper and TV accounts
seemingly indicating otherwise) occurs only at concentrations high enough to
result in other, more severe, toxic effects.
"Ozone
is a very reactive substance. It will readily react with just about any material
capable of being oxidized, and with many that are not. The material with which
it reacts may be a gas or vapor, a particle floating in the air (a mold spore,
for example), or a solid (or liquid) surface. For this reason, when ozone is
present in most enclosed spaces its concentration declines quite rapidly with
time. Of course, if ozone is being generated more rapidly than it is destroyed
by reaction, its concentration can build up. This is the main reason why
devices that produce relatively large amounts of ozone are safe only in
relatively large enclosures and why the ozone generation rate should be reduced
in small enclosures.
"Ozone
is well known for its ability to eliminate certain odors. How this is
accomplished is controversial. At concentrations just above the odor threshold,
some odors do seem to vanish. The main reason for this may be ozone's ability
to desensitize the olfactory apparatus so that the odors can no longer be
perceived. Some evidence indicates that this may be the case at least occasionally.
Other evidence indicates that ozone may react with the odor-causing substances,
eliminating them from the air (this is probably the only mechanism that
operates when concentrations are below the odor threshold).
"Finally,
some people have insisted that even if ozone does not paralyze the olfactory
sense, its odor is such that it "masks" other odors. Perhaps all
three mechanisms operate, each in its own area of effectiveness.
"As
with all other materials, ozone has a dose-effect relationship with a
threshold. That is, once the threshold dose has been exceeded, toxic effects
are proportional to dose. For inhaled gases, dose is proportional to both time
and concentration. If the duration of exposures cannot be controlled (as is
usually the case), then the concentration must be kept low enough so that no
injury will occur even from prolonged and repeated exposures.
For ozone, that
"threshold" concentration is 0.1 ppm. So long as concentrations are
kept at or below that level, injury is not expected even in the most sensitive
workers so long as their exposure durations coincide reasonably well with or
are less than the 8 hr/day, 40 hr/wk regimen. This "threshold" level
is accepted by the American Conference of Governmental Industrial Hygienists
(and is called the Threshold Limit Value by that organization) and by the
Occupational Safety and Health Administration, OSHA.
The TLV or OSHA's
Permissible Exposure Level (PEL) is not a fine line between safe and non-safe.
Instead, it represents the best judgment of a group of experts of the highest
concentration that can be inhaled repeatedly by a population of workers with no
resulting injury. Higher concentrations may or may not have any particular
effect on a specific individual.
"Ozone is a highly toxic gas
but even highly toxic substances can be encountered safely. The main concern
with this material is that concentrations to which people are exposed do not average more than 0.1 ppm over an 8-hr day, and do not exceed that value by more
than a factor of 2 or 3 during the 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
OZN-jr Ozone Generator, Sunlight Solutions, LLC., 2045 Niagara Falls Blvd. Suite 13 & 14, Niagara Falls, NY 14304 USA, Tel: 888-476-9269 - see
http://www.sunlightsheds.com/OZN-JR-Ozone-Generator-Ionizer.html
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Kansas State University, department of plant pathology, extension plant pathology web page on wheat rust fungus: see http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp
"A Brief Guide to Mold, Moisture, and Your Home",
U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
Allergen Tests in Buildings advice about how to test, what to look for, in evaluating the level of dog, cat, or other animal allergens in a building
"IgG Food Allergy Testing by ELISA/EIA, What do they really tell us?" Sheryl B. Miller, MT (ASCP), PhD, Clinical Laboratory Director, Bastyr University Natural Health Clinic - ELISA testing accuracy: Here is an example of Miller's critique of ELISA
http://www.betterhealthusa.com/public/282.cfm - Townsend Letter for Doctors and Patients
The critique included in that article raises compelling questions about IgG testing assays, which prompts our interest in actually screening for the presence of high levels of particles that could carry allergens - dog dander or cat dander in the case at hand.
http://www.tldp.com/issue/174/IgG%20Food%20Allergy.html contains similar criticism in another venue but interestingly by the same author, Sheryl Miller. Sheryl Miller, MT (ASCP), PhD, is an Immunologist and Associate Professor of Basic and Medical Sciences at Bastyr University in Bothell, Washington. She is also the Laboratory Director of the Bastyr Natural Health Clinic Laboratory.
Allergens: Testing for the level of exposure to animal allergens is discussed at http://www.animalhealthchannel.com/animalallergy/diagnosis.shtml (lab animal exposure study is interesting because it involves a higher exposure level in some cases
Allergens: WebMD discusses allergy tests for humans at webmd.com/allergies/allergy-tests
Animal Allergens: Dog, Cat, and Other Animal Dander - Cleanup & Prevention Information for Asthmatics and regarding Indoor Air Quality.
Recognizing Allergens: What various indoor allergens look like - identification photos to help identify pollen, dust mites, animal dander, toxic or allergenic mold - Common Mold and other Allergens, Irritants, Remedies & Advice
Rodent control issues, including dander, fecal, and urine contamination of Buildings and Building insulation are discussed at our
Associations: Sick House, Sick Building, SBS - Air Quality, Government, Private Associations and Information Resources
Atlas of Clinical Fungi, 2nd Ed., GS deHoog, J Guarro, J Gene, & MJ Figueras, Centraalbureau voor Schimmelcultures, Universitat Rovira I Virgili, 2000, ISBN 90-70351-43-9 (you can buy this book at Amazon)
Atlas of Indoor Mold, Online Clinical Mold Atlas, Toxins, Pathogens, Allergens and Other Indoor Particles - Medical Health Effects of Mold (separate online document)
Black Mold that is Harmless Photos of recognizable, usually harmless black mold on wood, bluestain, ceratocystis, ophistoma
Building Floods: quick steps after a building flood or plumbing leak can prevent costly mold contamination
Classes of Mold: what types of cosmetic, allergenic, or toxic mold are a problem? Can mold be cleaned-up successfully?
"A Brief Guide to Mold, Moisture, and Your Home", U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
"Disease Prevention Program for Certain Vegetable Crops," David B. Langston, Jr., Extension Plant Pathologist - Vegetables, University of Georgia (PDF document) original source: www.reeis.usda.gov/web/crisprojectpages/209797.html
"Disease Prevention in Home Vegetable Gardens,"
Patricia Donald,
Department of Plant Microbiology and Pathology,
Lewis Jett
Department of Horticulture, University of Missouri Extension - extension.missouri.edu/publications/DisplayPub.aspx?P=G6202
Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, is available from the InspectAPedia online bookstore - we recommend the CD-ROM version of this book. This 3rd/edition is a compact but comprehensive encyclopedia of all things mycological. Every aspect of the fungi, from aflatoxin to zppspores, with an accessible blend of verve and wit. The 24 chapters are filled with up-to-date information of classification, yeast, lichens, spore dispersal, allergies, ecology, genetics, plant pathology, predatory fungi, biological control, mutualistic symbioses with animals and plants, fungi as food, food spoilage and mycotoxins.
OTHER IAQ ISSUES: How To Find and Address Other Indoor Air or Indoor Environment Contaminants Besides Mold
Mold or allergens may not be the only or even the main indoor environmental contaminant. Don't let media attention to mold
cause so much enviro-scare fear that other, possibly more urgent hazards go un-addressed.
Ozone Warnings - Use of Ozone as a "mold"
remedy is ineffective and may be dangerous.
Pet control - if you can't say goodbye to your bird, cat, dog, guinea pig, hamster, tropical fish, then limit the
areas they occupy and limit the airflow from that area to sleeping or other areas of the building, use allergenic
bedding, eliminate wall-to-wall carpeting, improve housecleaning including use of a HEPA-rated vacuum cleaner. For more details
see our article Dog, Cat, and Other Animal Dander - Information for Asthmatics and Indoor Air Quality
Rodents, Mice, Squirrel Control - I find high levels of mouse and rodent dander, fecal dust, and urine-contaminated dust in some buildings,
and high levels of these materials in building insulation in those locations. If you have a mouse problem, particularly if mice and their waste (fecals or urine) are contaminating
the building HVAC or building insulation, may need both steps to clean up or remove infected materials and steps to stop an ongoing
rodent problem. If squirrels are a problem, the cleanup needs to include closing off entry openings into the building. Get some
help from a licensed pest control expert.
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