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Ozone generators & Ozone based air purifiers & air cleaners:
Do ozone generators and air purifiers work? Are ozone generators, mold treatments, deodorizers, and air purifiers recommended? As reported by the U.S. EPA, ozone generators that are sold as air cleaners intentionally produce the gas ozone.
Often the vendors of ozone generators make statements and distribute material that lead the public to believe that these devices are always safe and effective in controlling indoor air pollution. Page to photo: one of our ozone gas detector test instruments using a Draeger bellows pump and a colorimetric gas sampling tube.
We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
Are Ozone-Based Air Purifiers or Air Cleaners Effective, Safe, Recommended?
For almost a century, health professionals have refuted these claims (Sawyer, et. al 1913; Salls, 1927; Boeniger, 1995; American Lung Association, 1997; Al-Ahmady, 1997). The purpose of this document is to provide accurate information regarding the use of ozone-generating devices in indoor occupied spaces. This information is based on the most credible scientific evidence currently available.
In inspecting and testing many buildings we often encounter both owners and consultants who try to solve an existing problem by treating the symptom (for example an odor) rather than by treating the cause (a dead animal, for example, or insufficient fresh air intake, for another example).
The best ways to get rid of an indoor odor or airborne particle contaminant are:
Find and remove the odor source or problem particle source (such as dust, pet allergens, mold).
Make sure there is adequate fresh air intake for the building
Use high quality air filtration to reduce the level of circulating dust indoors.
The proper way to get rid of an indoor mold problem is to remove the problem mold and correct the conditions that caused it to grow. Attempts to rely on odor killers, mold killers, deodorants, or ozone generators are futile and may be harmful. Details follow.
Ozone-generating Air Cleaners are NOT RECOMMENDED to Purify Indoor Air and NOT RECOMMENDED as a Mold Treatment
Ozone Indoors - Bottom line:
At airborne concentrations of ozone which are safe, that is, are unlikely to be a hazard to humans, ozone is ineffective at removing contaminants.
At high levels in indoor air, ozone is likely to be hazardous to building occupants, and in our direct experience its use at high levels indoors can lead to surprise chemical reactions and oxidations of other building materials that in turn lead to new indoor odor, VOC, and other problems.
Notice: our discussion of the ineffectiveness of ozone as an indoor air cleaner and the potential hazards of indoor use of ozone for deodorizing, cleaning, or killing mold, is focused on the issues surrounding ozone and equipment that produces it indoors. AHAM , The Association of Home Appliance Manufacturers, certifies the effectiveness of various types of portable air cleaners.
Some vendors suggest that ozone-generating devices have been approved by the federal government for use in occupied spaces. This is not the case.
Watch out: The U.S. EPA emphasizes in its own publications that
NO agency of the federal government has approved these [ozone generating] devices for use in occupied spaces.
Because of these claims, and because ozone can cause health problems at high concentrations, several federal government agencies have worked in consultation with the U.S. Environmental Protection Agency to produce this public information document.
How is Indoor Ozone Gas Harmful to People
The same chemical properties that allow high concentrations of ozone to react with organic material outside the body give it the ability to react with similar organic material that makes up the body, and potentially cause harmful health consequences. When inhaled, ozone can damage the lungs (see - "Ozone and Your Health" - www.epa.gov/airnow/brochure.html ).
Relatively low amounts can cause chest pain, coughing, shortness of breath, and, throat irritation.
Ozone may also worsen chronic respiratory diseases such as asthma and compromise the ability of the body to fight respiratory infections. People vary widely in their susceptibility to ozone. Healthy people, as well as those with respiratory difficulty, can experience breathing problems when exposed to ozone.
Exercise during exposure to ozone causes a greater amount of ozone to be inhaled, and increases the risk of harmful respiratory effects.
Recovery from the harmful effects can occur following short-term exposure to low levels of ozone, but health effects may become more damaging and recovery less certain at higher levels or from longer exposures (US EPA, 1996a, 1996b).
Manufacturers and vendors of ozone devices often use misleading terms to describe ozone.
Terms such as "energized oxygen" or "pure air" suggest that ozone is a healthy kind of oxygen. Ozone is a toxic gas with vastly different chemical and toxicological properties from oxygen. Several federal agencies have established health standards or recommendations to limit human exposure to ozone.
Ozone-generating Air Cleaners Used to Remove Odors May Produce Excessive levels of Ozone Gas and May Cause Problematic Chemical Reactions with Other Building Contents
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." 
While expert use of ozone can be successful in some deodorizing applications, we have received primarily complaints from people who tried using ozone to get rid of indoor odors only to find that they had made things worse.
Question on Getting Rid of New Smells After Using an Ozone Generator Indoors:
I was hoping that you may have some suggestions on how to rid a house of the left over odor or chemicals, from using an ozone generator.
It's a long story, but I used a high powered ozone generator in my house, to get rid of skunk smell. Now I can't get rid of the left over nitric oxide, or whatever odor or gases, that linger in my house. I have been leaving the windows open every day, with running the heat on high (85 degrees) at night, to try to force off-gas the odors/gases.
All I can find is where others have had the same thing happen, and they ended up having to leave their homes. we are still hoping I can find a way to rid my house of the problem. - Nadine -
We have investigated a number of post-ozone treatment complaints and have been able to resolve the problem successfully, but not always at low cost. Ozone gas itself is very reactive - an oxidant. It does not stay around long after it has been generated in a building unless there is a continuing source such as an ozone generator still at work.
But when high levels of ozone have been produced in an enclosed space, we find that other materials in the space become partly oxidized, subsequently giving off horrible, often chemical-like odors. We have traced odors to painted surfaces, furniture, upholstery, curtains, carpeting, carpet padding, and other materials.
Following this procedure we can often narrow down the source of post-ozone-treatment smells to a single material that can then be removed or remedied, such as carpet padding or a specific piece of furniture.
Ozone-Generating Air Cleaners and Indoor Air Chemistry
The following data is obtained from "Ozone-Generating Air Cleaners and Indoor Air Chemistry" , a U.S. EPA Document
Ozone-generating air cleaners are marketed to homeowners as well as business establishments ostensibly to remove odors and other contaminants from indoor air.
IEMB has characterized ozone and oxides of nitrogen (NOx) emissions from these devices in full-scale environmental chamber tests and characterized performance in a research test house.
To date, findings demonstrate that, for those models tested, ozone generation rates are generally within the ranges stated by the manufacturers and some models have the capacity to generate ozone concentrations of 200 parts per billion (ppb) in the test house, well above EPA's 8-hour ambient ozone standard of 80 ppb.
Additionally, ozone and nitrogen dioxide emission rates increase with decreasing relative humidity, and the relationship between ozone emission rate and NOx generation rate varies between different models of different manufacturers.
Ozone-generating air cleaners equipped with an ozone sensor/controller designed to prevent activation of the ozone generator at concentrations above 50 ppb performed erratically in full-scale chamber tests but appeared to perform as designed in limited short-term (24 h) tests in a research test house.
We [the U.S. EPA] conclude that more extensive testing is needed to characterize the sensor/controller. However, tests in the research test house clearly demonstrate that these devices are capable of producing ozone concentrations well above those of accepted health guidelines.
IEMB is currently investigating the impact of ozone generators on concentrations of volatile organic compounds (VOCs) in indoor environments. These experiments investigate the chemical reactions that take place when an ozone-generating air cleaner is operated in the presence of emissions from a typical source of VOCs, such as an air freshener or cleaning product.
Results demonstrate that the ozone-generating air cleaners have little impact on airborne concentrations of solvents used in consumer products, but do impact concentrations of many of the fragrance compounds emitted by this type of product.
Reaction products include formaldehyde and other oxygenated organics.
The interaction between ozone and some of the product emissions, such as terpenes, triggers formation of ultra fine particles. IEMB is currently refining analytical approaches to better characterize the "soup" of particles and gases that results from operation of these devices in the presence of VOCs.
Apartment manager treated my apartment with ozone generator, ruined carpet, killed my plants, I have chest pain
I was told by an apartment manager when I moved in to my new apartment that it was a smoke free facility and when I was ready to move in,I went in the apartment they had for me and it smelled of cigarette smoke. I told her that I had allergies to cigarette smoke, so I couldn't move in and she said that they would repaint and clean the carpet so that I could move in.
Originally she told me that if any of the residents had smoked in their apartments that they would replace the carpet and they didn't do that for me. What I found out later is that there had been two chain smokers that had lived in this apartment. So they said they would put an ozonator in here and that the smell would go away and said it was okay for me to be in the apt while it was on.
I have had chest pain on my right lung now for three months and have no energy and am having a very hard time seeing specialists because of this. She told me that they would not replace the carpet when I moved in because they had just replaced it when earlier she told me that they would.
All she has done since I have been here is lie to me.Do not use an ozonator and be present and remove all plants as my big fig tree leaves turned black. So what do you think it has done to my lungs? - Jan-Marie 3/15/12
As we replied to Josh in that Q&A, by no means do we advocate panic about ozone exposure, but it is quite evident that some applications of ozone make sense and others do not.
There we also note the ozone issues arising from over-dosing or over-exposing building interiors and contents just as you describe. Details about oxidizing damage from over-doing an ozone treatment are at OZONE TOXICITY.
Question: How much plant area is needed to remove indoor ozone
2018/11/04 Andrea said:
We live near Los Angeles and on some days the ozone levels are much higher than others. We live in a tiny efficiency--just 180sf. We air out the place very early in the morning before there is much traffic and while the ozone levels are low. However, just opening the door several times a day and running the bathroom fan during showers brings in outdoor air through breezy door "seal."
How much plant leaf surface area should I have in the form of houseplants indoors to do a good job of removing ozone from this tiny home?
I have outdoor plants that I can bring inside, with the limitation being space to place them. I also have a basil plant that is very healthy and bushy and that I keep near my OttLite full spectrum desk lamp. We will be moving to a 2BR, 2.5BA duplex with a garage below, so that adds the potential for small amounts of exhaust to seep into the home if they remain after the garage door is shut.
Other than airing things out and outfitting the home with lots of plants, is there anything else I can do? I thought I'd tighten the seal on the inside garage door and air out as usualy when the O3 is at it's lowest level.
Reply: research on how much plant leaf area you need to remove ozone from your home.
Citing research I can clarify your concern about how much plant leaf area you need to remove ozone from your home.
It is correct that plants, at least in cool conditions, absorb some ozone, removing it from air through the stomata (small openings) in plant leaves.
Without an actual measure of the ozone level in a space and scientific data on the ozone removal rate of a specific plant leaf (genera, species, area, and growing conditions such as temperature and humidity) no quantitative guess is accurate and in my view would be mere fantasy.
Using a specific plant that can remove a lot of ozone (pothos) a total plant leaf surface area in square meters that is equal to room volume in cubic meters is as close as you'll get to a less than 20% effectiveness.
This scientific article is pertinent and worth a look:
Abbass, Omed A., David J. Sailor, and Elliott T. Gall. "Effectiveness of indoor plants for passive removal of indoor ozone." Building and Environment 119 (2017): 62-70.
Indoor vegetation is often proposed as a passive approach for improving indoor air quality. While studies of outdoor environments indicate that vegetation can be an important sink of outdoor ozone, there is scant data in the literature concerning the dynamics of ozone uptake by indoor plants. This study determined ozone deposition velocities (vd) for five common indoor plants (Peace Lily, Ficus, Calathia, Dieffenbachia, Golden Pothos).
The transient vd was calculated, using measured leaf areas for each plant, for exposures mimicking three diurnal cycles where ozone concentrations in chamber tests were elevated for 8 h followed by 16 h in the absence of ozone. Estimates of vd at the end of the first exposures ranged from 5.6 m h−1 for Golden Pothos to 0.9 m h−1 for Peace Lily.
Values of vd were approximately 50% and 66% lower at the end of a second exposure and third exposure, respectively. Estimates of vd were also made for a range of photosynthetic active radiation (PAR) levels typically observed indoors. An increase in PAR from 0.6 to 41.2 μmol m−2 sec−1 resulted in increases in vd ranging from a factor of 1.7 (Diffenbachia) to 4.7 (Peace Lily).
For deposition velocities measured in this study, the ozone removal effectiveness ranges from 0.9% to 9% for leaf surface area to room volume ratio of 0.06 m−1 (approximately one plant for every 1.8 m2 of floor area) when accounting for values of air exchange and background loss typical of a residential environment.
However, indoors, In my view the answer is zero. Only if there were a continuous source of ozone indoors should such steps be a serious consideration.
Ozone is a highly reactive molecule: it does not accumulate nor hang around.
These articles are also helpful in answering the question of the effectiveness of indoor plants at removing indoor ozone:
Abstract: Fifteen air cleaners, representing different technologies
and types of devices, were tested with a mixture of 16 representative
VOCs (17 VOCs in tests for products associated with
ozone generation) in a full-scale stainless steel chamber by
using a “pull-down” test method. Their initial performance
was evaluated in terms of single-pass efficiency (η) and the
clean air delivery rate (CADR).
include sorption filtration, ultraviolet-photocatalytic oxidation
(UV-PCO), ozone oxidation, air ionization (plasma
decomposition), and botanical air cleaning. Based on test
results, the relative effectiveness of the available technologies
tested and the effect of product configuration and VOC properties
on the VOC removal efficiencies are analyzed.
of test results on the development of a standard test
method for performance evaluation of gas-phase air cleaners
is also discussed briefly in this paper.
Guieysse, Benoit, Cecile Hort, Vincent Platel, Raul Munoz, Michel Ondarts, and Sergio Revah. "Biological treatment of indoor air for VOC removal: Potential and challenges." Biotechnology advances 26, no. 5 (2008): 398-410.
Yang, Dong Sik, Svoboda V. Pennisi, Ki-Cheol Son, and Stanley J. Kays. "Screening indoor plants for volatile organic pollutant removal efficiency." HortScience 44, no. 5 (2009): 1377-1381.
Yoo, Mung Hwa, Youn Jung Kwon, Ki-Cheol Son, and Stanley J. Kays. "Efficacy of indoor plants for the removal of single and mixed volatile organic pollutants and physiological effects of the volatiles on the plants." Journal of the American Society for Horticultural Science 131, no. 4 (2006): 452-458.
"Ozone-Generating Air Cleaners and Indoor Air Chemistry" , U.S. Environmental Protection Agency, original document is available at: epa.gov/appcdwww/iemb/ozone.htm
"Ozone Generators that are Sold as Air Cleaners", U.S. Environmental Protection Agency, original document is available at: epa.gov/iaq/pubs/ozonegen.html "EPA reviewed a wide assortment of this literature, including information provided by a leading manufacturer of ozone generating devices. In keeping with EPA's policy of insuring that the information it provides is based on sound science, only peer reviewed, scientifically supported findings and conclusions were relied upon in developing this document."
Association of Home Appliance Manufacturers (AHAM) 1111 19th Street, NW, Suite 402, Washington, DC 20036, (202) 872-5955 www.aham.org provides information on air cleaners on their AHAM-certified Clean Air Delivery Rate site at www.cadr.org AHAM conducts four certification programs for each category - room air cleaners, room air conditioners, dehumidifiers and refrigerator/freezers. The air cleaner certification program is known as AC-1.
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
US EPA - Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
US EPA - Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol
Allergies, Allergens, Allergy Testing in Buildings - References & Products
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) - The Atlas of Clinical Fungi is also available on CD ROM
"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 in Home Vegetable Gardens,"
Department of Plant Microbiology and Pathology,
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.
Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.
Rot concerns in buildings-some building mold such as Meruliporia incrassata "Poria" risks serious rot and hidden structural damage
US EPA: Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol
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.
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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