Air Purifying Ionizers May Produce Hazardous Levels of Ozone

By Heartspring Staff

Ozone, produced by air purifying ionizers, may be another example of how, "to much of a good thing can be bad." Normal background levels ozone will measure 10 parts per billionExit Site, attracting dust particles to stick on nearby surfaces, helping to naturally clean the air. However, ozone, artificially produced in a closed environment, has the potential to create hazardous conditions for humans. At higherconcentrations, breathing ozone isidentified as having toxic effects, according to OSHAstandardsExit Site.

Excess Ozone, O3, in the presence of a terpene source (such as a pine oil-based cleaner) can produceharmful secondary organic aresols. The major outcomes of this indoor air chemistry are formaldehyde (a known carcinogen) and secondary organic aeresols (ultrafine particles). To assess the effects of elevated indoor ozone levels researchers have included the ozone, formaldehyde and the ultrafine particles. All three can have a detrimental effect on human health.

According to the California Air Resources Board survey,Exit Site the majority of people who purchase an air cleaner do so because of allergies, asthma, other respiratory diseases or some other health concern. Buyers with these health conditions may have an increasedrisk to the air born effects of ozone and ozone chemistry generated byproducts.

Can excess levels of O3 be detected?

Ozone testing decives like the Trifield Air Ion CounterExit Site measure ions per cubic centimeters. Currently, there are no low cost air ion meters, offering feedback to automatically power an ionizer on, or off.

Quantification of ozone levels in indoor environments generated by ionization and ozonolysis air purifiers.

Journal of Air Waste Management Association. 2006 May;56(5):601-10.

Britigan N, Alshawa A, Nizkorodov SA. Department of Chemistry, University of California, Irvine 92697, USA.

Indoor air purifiers are advertised as safe household products for health-conscious individuals, especially for those suffering from allergies and asthma. However, certain air purifiers produce ozone (O3) during operation, either intentionally or as a byproduct of air ionization. This is a serious concern, because O3 is a criteria air pollutant regulated by health-related federal and state standards. Several types of air purifiers were tested for their ability to produce ozone in various indoor environments at 40-50% relative humidity, including office rooms, bathrooms, bedrooms, and cars. O3 levels generated by personal wearable air purifiers were also tested. In many cases, O3 concentrations were well in excess of public and/or industrial safety levels established by U.S. Environmental Protection Agency, California Air Resources Board, and Occupational Safety and Health Administration. Simple kinetic equations were obtained that can predict the steady-state level of O3 in a room from the O3 emission rate of the air purifier and the first-order decay rate of O3 in the room. The additivity of O3 levels generated by independent O3 generators was experimentally demonstrated. PMID:16739796

Effects of an ozone-generating air purifier on indoor secondary particles in three residential dwellings.

Indoor Air. 2005 Dec;15(6):432-44

Hubbard HF, Coleman BK, Sarwar G, Corsi RL. Department of Civil, Architectural and Environmental Engineering, Center for Energy & Environmental Resources, The University of Texas at Austin, Austin, TX 78758, USA.

The use of indoor ozone generators as air purifiers has steadily increased over the past decade. Many ozone generators are marketed to consumers for their ability to eliminate odors and microbial agents and to improve health. In addition to the harmful effects of ozone, recent studies have shown that heterogeneous and homogeneous reactions between ozone and some unsaturated hydrocarbons can be an important source of indoor secondary pollutants, including free-radicals, carbonyls, carboxylic acids, and fine particles. Experiments were conducted in one apartment and two detached single-family dwellings in Austin, TX, to assess the effects of an ozone generator on indoor secondary organic aerosol concentrations in actual residential settings. Ozone was generated using a commercial ozone generator marketed as an air purifier, and particle measurements were recorded before, during, and after the release of terpenes from a pine oil-based cleaning product. Particle number concentration, ozone concentration, and air exchange rate were measured during each experiment. Particle number and mass concentrations increased when both terpenes and ozone were present at elevated levels. Experimental results indicate that ozone generators in the presence of terpene sources facilitate the growth of indoor fine particles in residential indoor atmospheres. Human exposure to secondary organic particles can be reduced by minimizing the intentional release of ozone, particularly in the presence of terpene sources. PRACTICAL IMPLICATIONS: Past studies have shown that ozone-initiated indoor chemistry can lead to elevated concentrations of fine particulate matter, but have generally been completed in controlled laboratory environments and office buildings. We explored the effects of an explicit ozone generator marketed as an air purifier on the formation of secondary organic aerosol mass in actual residential indoor settings. Results indicate significant increases in number and mass concentrations for particles <0.7 microns in diameter, particularly when an ozone generator is used in the presence of a terpene source such as a pine oil-based cleaner. These results add evidence to the potentially harmful effects of ozone generation in residential environments. PMID:16268833

Cleaning products and air fresheners: emissions and resulting concentrations of glycol ethers and terpenoids.

Indoor Air. 2006 Jun;16(3):179-91.

Singer BC, Destaillats H, Hodgson AT, Nazaroff WW. Atmospheric Sciences Department, Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.

Experiments were conducted to quantify emissions and concentrations of glycol ethers and terpenoids from cleaning product and air freshener use in a 50-m3 room ventilated at approximately 0.5/h. Five cleaning products were applied full-strength (FS); three were additionally used in dilute solution. FS application of pine-oil cleaner (POC) yielded 1-h concentrations of 10-1300 microg/m3 for individual terpenoids, including alpha-terpinene (90-120), d-limonene (1000-1100), terpinolene (900-1300), and alpha-terpineol (260-700). One-hour concentrations of 2-butoxyethanol and/or d-limonene were 300-6000 microg/m3 after FS use of other products. During FS application including rinsing with sponge and wiping with towels, fractional emissions (mass volatilized/dispensed) of 2-butoxyethanol and d-limonene were 50-100% with towels retained, and approximately 25-50% when towels were removed after cleaning. Lower fractions (2-11%) resulted from dilute use. Fractional emissions of terpenes from FS use of POC were approximately 35-70% with towels retained, and 20-50% with towels removed. During floor cleaning with dilute solution of POC, 7-12% of dispensed terpenes were emitted. Terpene alcohols were emitted at lower fractions: 7-30% (FS, towels retained), 2-9% (FS, towels removed), and 2-5% (dilute). During air-freshener use, d-limonene, dihydromyrcenol, linalool, linalyl acetate, and beta-citronellol) were emitted at 35-180 mg/day over 3 days while air concentrations averaged 30-160 microg/m3. PRACTICAL IMPLICATIONS: While effective cleaning can improve the healthfulness of indoor environments, this work shows that use of some consumer cleaning agents can yield high levels of volatile organic compounds, including glycol ethers--which are regulated toxic air contaminants--and terpenes that can react with ozone to form a variety of secondary pollutants including formaldehyde and ultrafine particles. Persons involved in cleaning, especially those who clean occupationally or often, might encounter excessive exposures to these pollutants owing to cleaning product emissions. Mitigation options include screening of product ingredients and increased ventilation during and after cleaning. Certain practices, such as the use of some products in dilute solution vs. full-strength and the prompt removal of cleaning supplies from occupied spaces, can reduce emissions and exposures to 2-butoxyethanol and other volatile constituents. Also, it may be prudent to limit use of products containing ozone-reactive constituents when indoor ozone concentrations are elevated either because of high ambient ozone levels or because of the indoor use of ozone-generating equipment. PMID:16683937

Buying a Safe Air Ionizer?

Hazardous Ozone-Generating Air PurifiersExit Site lists safe, and unsafe, air purifying ionizers, certified by the California Environmental Protection Agency.

Ed Sherbenou explains the potential health issues concering air ionizers at Air Purifier PowerExit Site

Tropospheric “Surface" Ozone

Although ozone high up in the stratosphere provides a shield to protect life on Earth, direct contact with ozone is harmful to both plants and animals (including humans). Ground-level, “bad," ozone forms when nitrogen oxide gases from vehicle and industrial emissions react with volatile organic compounds (carbon-containing chemicals that evaporate easily into the air, such as paint thinners). In the troposphere near the Earth’s surface, the natural concentration of ozone is about 10 parts per billion (0.00001 percent). According to the Environmental Protection Agency, exposure to ozone levels of greater than 80 parts per billion for 8 hours or longer is unhealthy. Such concentrations occur in or near cities during periods where the atmosphere is warm and stable. The harmful effects can include throat and lung irritation or aggravation of asthma or emphysema. Ozone Hole WatchExit Site


Heartspring Staff are assistants of board reviewed doctors that are medical editors, authors, and reviewers, providing oversight for This article is currently undergoing doctor reveiw.


Growing Clean Air
Three common house plant species to clean, and produce enough air to supply an enclosed living environment.