There are many so-called air purifiers on the market that are, in fact, ozone generators. According to the American Lung Association, "Ozone is a potent lung irritant and exposure to elevated levels is a contributor to the exacerbation of lung disease; it is especially dangerous for persons with asthma and other chronic lung diseases, children and the elderly."

And don't be fooled by products claiming to be negative ion generators. Again, according to the American Lung Association, there is no difference between a negative ion generator and an ozone generator.

Consumer Reports (1992), the National Institute of Occupational Safety and Health (NIOSH), and the U.S. EPA concluded that tabletop and room unit ozone generators are not effective in improving indoor air quality! Studies have found that while some indoor air pollutant concentrations decline in the presence of ozone, other pollutants increase.

In fact, upon reaction with ozone, some previously undetected, toxic chemicals emerge in indoor air! These include formaldehyde and other aldehydes.

Not only that, there is a lack of research that indicates that low concentrations of ozone remove organic contaminants in the air. And at higher concentrations of ozone, (especially above 0.08 ppm) ozone is a potent irritant that can bring about diminished lung function, cough, inflammation associated with biochemical changes and increased responsiveness to allergens.

Current evidence of the health effects of ozone suggests that there is no "safe" threshold level of ozone above exposure to background levels. Also, exposure to ozone mixed with other compounds may produce combined and increased negative effects! And if you already have asthma you likely have increased susceptibility to ozone and exposure to even low concentrations of ozone can result in increased symptoms, medications use and even hospitalization!

The bottom line is that ozone generators and negative ion generators may produce levels of ozone recognized as unsafe for humans and are not recommended by the ALA for use in occupied spaces because of the risk of ozone!

The American Lung Association does not suggest the use of these products.

Ozone Can Cause Asthma in Kids

The American Lung Association recently reported that ozone can actually cause children to become asthmatic. They reported:

According to a University of California Davis study, allergies and respiratory problems caused by poor air quality can lead to asthma in children, TheKCRAChannel.com reported on Apr. 17. Twenty to 25 percent of patients develop asthma caused by allergies, according to the report. The Davis study says that smog and high levels of ozone can change lung development, making them hypersensitive to allergens. If ozone can do this much damage to developing lungs, anyone concerned with indoor air should steer clear of air filtration machines that emit ozone!


Introduction and Purpose

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. 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.

Some vendors suggest that these devices have been approved by the federal government for use in occupied spaces. To the contrary, NO agency of the federal government has approved these 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.

Table 1. Ozone Heath Effects and Standards
Health EffectsRisk FactorsHealth Standards*
Potential risk of experiencing:

Decreases in lung function

Aggravation of asthma

Throat irritation and cough

Chest pain and shortness of breath

Inflammation of lung tissue

Higher susceptibility to respiratory infection Factors expected to increase risk and severity of health effects are:

Increase in ozone air concentration

Greater duration of exposure for some health effects

Activities that raise the breathing rate (e.g., exercise)

Certain pre-existing lung diseases (e.g., asthma)
The Food and Drug Administration (FDA) requires ozone output of indoor medical devices to be no more than 0.05 ppm.

The Occupational Safety and Health Administration (OSHA) requires that workers not be exposed to an average concentration of more than 0.10 ppm for 8 hours.

The National Institute of Occupational Safety and Health (NIOSH) recommends an upper limit of 0.10 ppm, not to be exceeded at any time.

EPA’s National Ambient Air Quality Standard for ozone is a maximum 8 hour average outdoor concentration of 0.08 ppm (see - the Clean Air Act - www.epa.gov/air/caa/title1.html#ib)

(* ppm = parts per million)

Are Ozone Generators Effective in Controlling Indoor Air Pollution?

Available scientific evidence shows that at concentrations that do not exceed public health standards, ozone has little potential to remove indoor air contaminants.

Some manufacturers or vendors suggest that ozone will render almost every chemical contaminant harmless by producing a chemical reaction whose only by-products are carbon dioxide, oxygen and water. This is misleading.First, a review of scientific research shows that, for many of the chemicals commonly found in indoor environments, the reaction process with ozone may take months or years (Boeniger, 1995). For all practical purposes, ozone does not react at all with such chemicals. And contrary to specific claims by some vendors, ozone generators are not effective in removing carbon monoxide (Salls, 1927; Shaughnessy et al., 1994) or formaldehyde (Esswein and Boeniger, 1994).
  Second, for many of the chemicals with which ozone does readily react, the reaction can form a variety of harmful or irritating by-products (Weschler et al., 1992a, 1992b, 1996; Zhang and Lioy, 1994). For example, in a laboratory experiment that mixed ozone with chemicals from new carpet, ozone reduced many of these chemicals, including those which can produce new carpet odor. However, in the process, the reaction produced a variety of aldehydes, and the total concentration of organic chemicals in the air increased rather than decreased after the introduction of ozone (Weschler, et. al., 1992b). In addition to aldehydes, ozone may also increase indoor concentrations of formic acid (Zhang and Lioy, 1994), both of which can irritate the lungs if produced in sufficient amounts. Some of the potential by-products produced by ozone’s reactions with other chemicals are themselves very reactive and capable of producing irritating and corrosive by-products (Weschler and Shields, 1996, 1997a, 1997b). Given the complexity of the chemical reactions that occur, additional research is needed to more completely understand the complex interactions of indoor chemicals in the presence of ozone.
  Third, ozone does not remove particles (e.g., dust and pollen) from the air, including the particles that cause most allergies. However, some ozone generators are manufactured with an "ion generator" or "ionizer" in the same unit. An ionizer is a device that disperses negatively (and/or positively) charged ions into the air. These ions attach to particles in the air giving them a negative (or positive) charge so that the particles may attach to nearby surfaces such as walls or furniture, or attach to one another and settle out of the air. In recent experiments, ionizers were found to be less effective in removing particles of dust, tobacco smoke, pollen or fungal spores than either high efficiency particle filters or electrostatic precipitators. (Shaughnessy et al., 1994; Pierce, et al., 1996). However, it is apparent from other experiments that the effectiveness of particle air cleaners, including electrostatic precipitators, ion generators, or pleated filters varies widely (U.S. EPA, 1995).

If used at concentrations that do not exceed public health standards, ozone applied to indoor air does not effectively remove viruses, bacteria, mold, or other biological pollutants?

Some data suggest that low levels of ozone may reduce airborne concentrations and inhibit the growth of some biological organisms while ozone is present, but ozone concentrations would have to be 5 - 10 times higher than public health standards allow before the ozone could decontaminate the air sufficiently to prevent survival and regeneration of the organisms once the ozone is removed (Dyas, et al.,1983; Foarde et al., 1997).

Even at high concentrations, ozone may have no effect on biological contaminants embedded in porous material such as duct lining or ceiling tiles (Foarde et al, 1997). In other words, ozone produced by ozone generators may inhibit the growth of some biological agents while it is present, but it is unlikely to fully decontaminate the air unless concentrations are high enough to be a health concern if people are present. Even with high levels of ozone, contaminants embedded in porous material may not be affected at all.

Can Ozone be Used in Unoccupied Spaces?

Ozone has been extensively used for water purification, but ozone chemistry in water is not the same as ozone chemistry in air. High concentrations of ozone in air, when people are not present, are sometimes used to help decontaminate an unoccupied space from certain chemical or biological contaminants or odors (e.g., fire restoration). However, little is known about the chemical by-products left behind by these processes (Dunston and Spivak, 1997). While high concentrations of ozone in air may sometimes be appropriate in these circumstances, conditions should be sufficiently controlled to insure that no person or pet becomes exposed. Ozone can adversely affect indoor plants, and damage materials such as rubber, electrical wire coatings, and fabrics and art work containing susceptible dyes and pigments (U.S. EPA, 1996a).


Whether in its pure form or mixed with other chemicals, ozone can be harmful to health.When inhaled, ozone can damage the lungs. Relatively low amounts of ozone can cause chest pain, coughing, shortness of breath and, throat irritation. It may also worsen chronic respiratory diseases such as asthma as well as compromise the ability of the body to fight respiratory infections.

Some studies show that ozone concentrations produced by ozone generators can exceed health standards even when one follows manufacturer’s instructions.Many factors affect ozone concentrations including the amount of ozone produced by the machine(s), the size of the indoor space, the amount of material in the room with which ozone reacts, the outdoor ozone concentration, and the amount of ventilation. These factors make it difficult to control the ozone concentration in all circumstances.

Available scientific evidence shows that, at concentrations that do not exceed public health standards, ozone is generally ineffective in controlling indoor air pollution.The concentration of ozone would have to greatly exceed health standards to be effective in removing most indoor air contaminants. In the process of reacting with chemicals indoors, ozone can produce other chemicals that themselves can be irritating and corrosive.


The public is advised to use proven methods of controlling indoor air pollution. These methods include eliminating or controlling pollutant sources, increasing outdoor air ventilation, and using proven methods of air cleaning.


Why HEPA Air Filters?

According to the American Lung Association, the HEPA filter is the most efficient filter for removing small particles that can be breathed deeply into the lungs. For this reason, we offer HEPA-type air filters exclusively because we believe that they provide the best way to remove irritating particles from the air you breathe.

To qualify as a HEPA air filter, an air filter must meet the government standard of removing 99.97% of all particles greater than .3 microns from the air that passes through the machine.  Ozone-type machines may actually cause asthma attacks and similar respiratory problems, without even removing the particulates. Electrostatic air filters lose efficiency as soon as they are used and must be constantly cleaned.

Why Dehumidify?

Two of the largest sources of allergens in the home are dust mites and mold spores. Common symptoms to dust mites are sneezing, nasal stuffiness, runny nose, itchy, and watery eyes and asthma attacks. Mold can cause even more serious health hazards such as coughing, wheezing, running eyes/nose, skin rashes and muscular aches, loss of appetite, inability to concentrate and fatigue.


Potentially Hazardous Ozone Generators Sold as Air Purifiers
Updated November 6, 2007 


Some devices that are advertised as "air purifiers", air cleaners, or ozone generators purposely emit large amounts of ozone, the main component of smog! Not only are such ozone generators ineffective at cleaning indoor air, but breathing ozone poses serious health risks. The Air Resources Board recommends that these ozone generators not be used.

The following is a partial list of portable air cleaners sold as "air purifiers" or ozone generators that can intentionally emit ozone. This list includes air cleaners sold primarily for residential use, plus some for commercial, in-vehicle, and personal use. Inclusion on this list is based on information available at the time of review. These devices have not been tested by the Air Resources Board using the test protocol required by the recently approved regulation, and until the testing required by the regulation is completed, we do not know if the ozone emitted will exceed the recently adopted 0.050 ppm standard. Exclusion from this list is not to be construed as endorsement by the California Air Resources Board. In-duct systems and other non-portable ozone generators are not listed here, but may generate potentially harmful levels of ozone.

This list (updated November 6, 2007) will be updated periodically as information becomes available.

  Air-Zone (All models)  
    XT-120, XT-240, XT-400, XT-800, XT-2000, XT-4000, XT-6000, XT-14000, XT-28000  
  Airdow (ADA Air Purifier and Air Cleaner (Xiamen) Co., Ltd)  
    ADA 311, 377, 388, 705, 706, 708, 717, 728, 729, 737, 739, 767  
  Allied Products/Biofeedback Instrument Corporation  
    Kleen-Air King II Model 1004A, 1004, 1004 SP, 1007  
    Living Air Classic, XL-15, Breeze AT, LA1, LA2, Peak, Flair, Fresh Air, Personal Air Purifier  
  Applied Ozone Systems  
    CS-1, CS-2  
  APSNA - Air & Water Purification Systems North America (All models)  
    FA1, C3, BAT, F2  
  Aqua Sun Ozone International  
    Model-(100, 202A, 206A, 217A, 308, 700, 5000), Model-2500/Kleenair, Model-2500R/Kleenair  
  Aran Aqua Pollution Control Systems  
    SS-Series Aranizers (SS-1, SS-3X, SS-4X, SS-6, SS-8, SS-10)
NS-Series Aranizers (NS-3, NS-5, NS-6, NS-8, NS-10)  
  Better Living  
    Sun Aire Air Purifier  
  BioTech Research  
    EdenPURE Area Air Purifier, EdenPURE Deluxe Air Purifier  
  Biozone (All models)  
    50, 100, 102, 500, 1000, 2000, 3000, 4000, 5000, Travel Aire 50V, Travel Aire 250T  
  Breathe Pure  
    QOZO-100, QOZO-500  
  Capital Vanguard Co., Ltd  
    HV-(107, 109, 202, 202A, 203A, 205, 206A, 207, 207A, 210A, 217A, 308), HV-202I+O3  
  Carspa Technology Co., Ltd  
    Car0100, Car0300, Car0400  
  Cliff Scott Enterprises (All models)  
    CSE 100, CSE 101  
    CD-100, CD-120, CD-210, CD-200, CD-2120, CD-2200  
  Crystal Air (All models)  
    CA45-2, DC Pro (200, 450, 970), Multizone 280, Pro (420, 700, 3400-1, 3600-1), UV Pro 550  
  Csonka (All models)  
    Original AirCare, Super AirCare, Pro AirCare, Automotive AirCare, Facility Control System AirCare, Car Fresh AirCare, Desk Fresh AirCare, Turbo Fresh AirCare  
  Detail King  
  EcoQuest (Most models)  
    Fresh Air, Living Air Classic, Breeze AT, Flair, Fresh Air To Go, EcoBox  
    H-50, XL-250 SH, TS-50, M10  
  Ez-com System, Inc.  
    EA-8705, EW-300, EW600, EW-900, GW-250  
  Enaly (Most models)  
    OZX-A200B, OZX-A500B, OZX-A3500, OZX-A700, OZX-7000B  
  Fresh-Aire (Triatomic Environmental, Inc.)  
  HealthWay Home Products, Inc.  
    Healthway Air Deodorizer HW-DE01  
  Hefei Sensing Electronic Co., Ltd.  
    Ozone Air Purifier  
  Imperial Products  
    Air Fresh G-100, Moonland Desktop Ozone Purifier, SL-002 High Output Ozone Air Purifier, XJ-1000 Ionic Air Purifier, XJ-3000B Professional Ozone Air Purifier  
  Jenesco (All models)  
    DC-12, PT101, PT101W, PT109, PT109W, PRO-4, PRO-8, FM-1,FM-2  
  King Air & Water Purification Corporation  
    See Allied Products  
  Lenntech (All models)  
    Series 3000  
    LA-1XP/2500, LightningAir Plus 5PX series, LA-2SPX  
  Longevity Resources  
    ZipZone, EnviroPro (420, 700, 3400, 3600, 3600-5)  
  Matsutek Enterprises Co., Ltd.  
    ION737, AR-150, CA-320, CA-721  
    N206a, N208  
  Natural Air  
    Natural Air  
  Nature's Air  
    DC Pro 450, Pro 700, DC Pro 970, UV Pro 550  
  Odatus (All models)  
    Odatus II  
  Oxytech Research (All models)  
    MGA-500, MGA-1000, MGA-2000, MGA-3500  
  Ozomax, Ltd.  
    Ozo Fresh 30  
  Ozone Environmental Technologies  
    Uvonair (1000, 3000, 5000)  
  Ozone Solutions (All models)  
    MZ-280, MZ-450, MZ-950, OMZ-420, OMZ-700, OMZ-1000, OUV-550, OMZ-2500, OMZ-3400  
  Peaceful Breeze  
    Small Room Air Purifier Model 388  
  Peak Pure Air  
    Peak O3 Air Purifier  
  Prozone (All Models)  
    PZ5-A, PZ2-2A, The Prozone (Purifier), Whole House Twister, PZ6-AIR, Whole House Air and Surface Purifier  
  Pure 'n Natural (Certain models)  
    OZ-2000 ( Odor Zapper ), Sani-Mate AS-250-B, NA50 Deodorizer/Air Freshener  
  QCH Tradelink  
  Quantum Pure Aire  
    AccuAire ALS-750, ALS-1500, ALS-3000, RMS-100, ClassicAire (CS-1000, CS-2000, CS-3500), XP-350  
  Queenaire Technologies, Inc.  
    QT Storm, QT Thunder, QT Thunder-24, QT Tornado, QT Cyclone, Newaire Plugin  
  Rain Fresh Air  
    RFA5000, RFA3500  
  RainbowAir (All models)  
    Newaire Plug In, Activator (250, 500, 1000)  
  Shenyang Bodycare Ozone Research Insitute  
    UV_Portable, UV_Wall Mount  
  SpringAir (Certain models)  
    CS-1, CS-2  
  Sun Aire  
    see Better Living  
  Surround Air (Certain models)  
  Taoture International Enterprises, Inc.  
    OZX-A200B, OZX-A500B  
  TriMed AirMedic  
    SBR-1, SBH-1, C12-1, C12-U1  
  TriStar Enterprises, LLC  
    PureStar XJ-3000D  
  Trump Electronic Company  
    TP-2, TP-3, TP-4, TP-5, TP-6, TCB-913GC  
  Ultra-Pure (Real Spirit USA, Inc.)  
    UP-988, UP-899, Pet-Pro 3800  
  Windchaser (Certain models)  
    IF-1, IF-2, IMC-1  
  Zhuhai Large Horse Electrical Appliances Co., Ltd.  
    HMA (300, 300/A, 300/A02, 300/H01, 300/H02, 300/RH, 300/RH01, 300/RH02, 600/O3)  
    Perfect Air Plug-In, PA 100, PA 200, PA 300, O3 Air Purification System