The Sharper Image Air Ionizer was a hot seller a few years ago, and a few models included an "Ozone" feature. This blue light would create O3, and supposedly were useful for cleaning the air.
I've read reports about the O3 emitted by this devices, and had personal experience with my mother getting asthma coincidentally at the same time the device was turned on in her apartment.
Can the ozone emitted by this device cause negative health effects?
From https://www.mayoclinic.com/health/asthma/AN00443
Answer from James T. Li, M.D.
Despite manufacturers' claims, ozone air purifiers don't remove asthma triggers from the air. In fact, inhaled ozone can make asthma worse.
Inhaling ozone, even in small amounts, can irritate the lungs. Specific effects may include throat irritation, coughing, chest pain and shortness of breath, as well as an increased risk of respiratory infections.
Another good source is https://www.epa.gov/apti/ozonehealth/effects.html - it has too many points of interest to cite, so I picked one study at random:
Use of inhaled beta-adrenergic agonist medication to alleviate asthma aggravation is plotted against ozone concentrations during summer asthma camps conducted for children 7 to 13 years old, during the last week of June, 1991 through 1993, in the Connecticut River Valley, downwind of New York City. Each child's normal physician-prescribed medications were maintained throughout each week. An increase in the 1-hour daily maximal ozone concentration from 84 to 160 ppb was significantly associated with increased unscheduled medications administered per day.
Source: Thurston et al., 1997
Ozone is claimed to be good at eliminating (not masking) odors, at least according to The O₃zone Experts, who sell equipment for industrial and commercial applications:
Ozone is very effective in eliminating odors including tobacco smoke, human and pet odors, food odors, mold and mildew odors, garbage odors, renovation odors and much more. It is not a re-odorant. It totally destroys the offending gases that are the source of everything we smell. Unlike many other deodorizing methods, ozone actually searches out and destroys the problem gases. It will react with contaminants in the air, water, fabrics and on other surface of the walls and ceilings. Unlike other types of air purification systems, an ozone generator does not depend on the air passing through the machine to do its job. Ozone generators also produce large quantities of ions via the corona discharge. The ions cause the dust particles to agglomerate, and precipitate from the air leaving a cleaner environment.
But:
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).
— Can Ozone be Used in Unoccupied Spaces? | US EPA [Their emphasis]
And:
Ozone (O₃) is a colorless to blue gas with a pungent odor. Exposure to ozone may cause headaches, coughing, dry throat, shortness of breath, a heavy feeling in chest, and fluid in the lungs. Higher levels of exposure can lead to more severe symptoms. Chronic exposure may lead to asthma. Workers may be harmed from exposure to ozone.
Why would anyone even think that breathing ozone is a good idea?
Surely the manual that came with the unit explained that the ozone mode should be used only when the area is going to be unoccupied by breathing creatures during ozone mode and for a few hours afterward.
I would guess that the problem here is improper use of the equipment by people that think they don't need to read the instructions and warnings that come with it. Either that, or a criminally negligent supplier.
Perhaps not criminally, but they eventually learned their lesson:
Consumer Reports stated that the Quadra could be dangerous to consumers' health because of the trace levels of ozone produced by the unit. As a result sales plummeted, and Sharper Image stores took back all units for a cash refund. The Sharper Image's response was to work with the Engelhard Corporation and create an ozone catalyst that reduced the amount of excess ozone in the purified air before it circulated throughout the room.
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Litigation involving its Ionic Breeze air purifiers sullied the brand's image. The company sued Consumer Reports for Fail ratings on ionic purifiers. In turn, the company was sued by customers for ineffective air purification.
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The Sharper Image stock price reached a record low of 29 cents a share on February 20, 2008. On February 25, 2008, The Sharper Image announced it had received notification that it would be delisted from the NASDAQ exchange. The company filed for bankruptcy protection with the U.S. Bankruptcy Court in Wilmington, Delaware after four years of sales losses and three straight years of losses.
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In 2011, Iconix Brand Group bought the Sharper Image brand and took control of all licensing relationships, while Camelot Venture Group continued to operate the catalog and website. In June 2014, Camelot Venture Group acquired the rights to the US direct-to-consumer division of the brand (catalog and e-commerce) from Iconix Brand Group.
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In December 2016, Irvine (California)-based ThreeSixty Group, owners of brands such as FAO Schwarz and Vornado Air, purchased all remaining rights (including global manufacturing, distribution, and licensing rights) from Iconix Brand Group for US$100 million (~$112 million in 2021). In 2019, ThreeSixty Group relaunched Sharper Image with new logos, styling, slogans (including Tomorrow's Tomorrow), and a refreshed product assortment.
In 2011 their Ionic Comfort Air Purifier ad said:
It even cleans ozone out of the air with patented technology that transforms ozone into oxygen.
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Indoor air purifier converts ozone to oxygen through a patented process
Today's Sharper Image's ad for their Airfree T800 Filterless Air Purifier says:
There are no harmful emissions such as UV light or ozone.
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Reduces indoor harmful ozone levels
