Bad odors that come from volatile organic compounds (VOCs) in the air are not only annoying but potentially bad for your health. Sometimes these odors can be so strong, traditional cleaning methods like using baking soda or white vinegar simply do not work. If you are confronted with such potent and potentially harmful odors in your home, car or place of work, you will likely consider more powerful ways to remove them.
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One of these methods involves using an ozone machine to eliminate bad smells.
We will explain how ozone generators work on specific problem odors, what precautions to take and possible scenarios for their use.
Ozone generators produce ozone by breaking oxygen molecules (O2) apart so that singular atoms can bond with other O2 molecules to form O3 (ozone). This is done in two ways: through silent corona discharge, which utilizes electric discharge to split the oxygen molecules, or via UV radiation to split oxygen molecules. Either way, the device generates ozone.
Manufacturers and retailers of ozone generators often claim that that these ozone molecules will chemically react with VOCs, bacteria, viruses, and other gaseous pollutants to kill the odor at the source. But according to research, ozone concentrations would take hundreds of years to break down VOCs in particular.
When ozone was used as a cleaning agent in some air purifiers to remove VOCs, removal efficiencies by ozone alone were low and particular harmful byproducts could be produced. Reactions between excessive residual ozone and unsaturated VOCs may even lead to the formation of harmful intermediates such as aldehydes, organic acids and fine mode particles. Furthermore, the reaction rates of ozone with most VOC's were slow in indoor environments.
While there are limited scientific studies to support ozone's usefulness in getting rid of odor completely, it is plausible that ozone will react with odorous chemicals. For example, ozone is believed to react with acrolein, one of the many odorous and irritating chemicals found in secondhand tobacco smoke. Ozone may also be effective in breaking down certain types of VOCs containing such as those in cooking oils, cleaning agents, etc.
Ozone generators are legally sold and marketed as air cleaners, but they produce ozone as a byproduct and have not been approved for use in occupied spaces by any federal agency. Here are a few precautions you should take if using an ozone generator:
Though all odor molecules are classified as volatile organic compounds (VOCs), here is how ozone might interact with specific problem odors you may encounter in your home:
As much as we love them, our pets are some of the most common sources of stinkiness in a house. Pet dander is composed of skin flakes and the most common source of that 'pet smell,' which can be hard to get rid of with traditional methods. For general pet odors in a room, an ozone machine might mask any smells that can be picked up by the human nose.
On the other hand, pet urine'a very common source of strong odor in carpets and porous materials'contains urea, which will not oxidize. Therefore, it is important to identify the source of your pet odor smells before choosing to use an ozone generator.
Long haul and short haul trucking companies that transport produce, livestock and many other items that leave behind a wide range of smells might require frequent odor removal in their vehicles. Depending on the extent of the problem, ozone generators can be run for several hours in these transportation vehicles (while unoccupied) to help eliminate some of the odors. However, as we discussed, the efficacy of ozone on VOCs is not certain and may be limited if applied in a short time period.
Smoke is difficult to remove from the air and is dangerous to inhale, so this is one of the odors you should take immediate steps to mitigate. Because it is a difficult odor to remove, people often try ozone and other more extreme odor removal methods. But there are some serious caveats about using ozone in this way. Brian W. Christman, a professor of medicine at Vanderbilt University and a spokesman for the American Lung Association, notes that ozone can be very hard on people with asthma or cardiovascular issues and may be harmful at high enough levels. Since smokers are at an increased risk for both asthma and cardiovascular disease, it is easy to understand the risks associated with using ozone to remove cigarette smoke.
Ozone might effectively mask smells produced by mold and mildew. But whether or not the ozone actually treats the mold issue will depend on several factors, including the extent of the problem, the source and type of mold. Nevertheless, ozone generators may still be a viable option for reducing mold and mildew odors because mold will oxidize under the conditions of high shock ozone treatment. This level of ozone is too high for exposure and requires the safety precautions discussed above.
Mold and mildew grow in dark and humid places where there is a lack of fresh oxygen. In all cases the moisture and humidity in the walls, floor etc., must first be removed or solved permanently to effectively eliminate the problem mold and odor. However, ozone can also be an unpleasant smell as well, so mitigating the mold issue this way may just be substituting one issue for another. Furthermore, it is likely that ozone generators are unable to remedy the cause of the mold, so it is still only a partial solution if at all.
Rental homes may reek with the smell of a past tenant. Strong body odors can linger and be difficult to air out by simply leaving windows open or through basic cleaning. In this case, an ozone generator may seem like a reasonable next step. However, past research indicates 'that body odor may be masked by the smell of ozone but is not removed by ozone.' Therefore in the case of human odors, it would make sense to try a non-ozone air purifier and other traditional forms of cleaning before turning to ozone with potentially limited efficacy.
There are a few situations for which people might consider renting an ozone generator. These are typically perceived as larger scale problems that require a more technical solution. Identifying the source of the odor, trying alternate elimination methods and assessing their overall cost effectiveness can help you decide if trying an ozone generator is worth it. It is important to take a measured and deliberate approach in deciding as you are introducing a potentially dangerous compound into your home, workspace or vehicle'will need to take steps to reduce the risks associated with the ozone.
A cost-effective option may be renting an ozone generator from your local home store. Rentable ozone generators can range from small, home-sized units to industrial behemoths. The cost to rent an ozone generator ranges from around $550 to $+. If you are only looking for a small unit, other home stores may offer modular, compact ozone generators for purchase, ranging from around $90 to $300.
If you decide to rent an ozone generator, you can take some steps to reduce the time required for the generator to be in use. Try cleaning the affected area with white vinegar or baking soda etc. to attack the source of the smell and possibly eliminate the problem in a less intensive manner. It typically costs $600 for someone to clean a 1,000-sq-foot home, though many high output ozone generator rentals can easily cost thousands.
When a house has a mold problem, people often use ozone generators to address the more obvious issues, like strong odors. However, you must be careful that the source of the mold (i.e. a leaking water source, fungal growth, etc.) is properly remediated by professionals. Ozone generators may mask the smell, but you will need to ensure you are not continuing to live with toxic mold growth by eliminating the root of the problem.
Work environments where a great deal of harmful, smelly compounds permeate the air may be a setting where ozone generators are occasionally used. Because employers are required by law to ensure a safe and compliant work environment, the use of ozone generators varies from site to site. Generally, specialists are consulted to ensure that the generator will not interact harmfully with worksite VOCs'otherwise it is likely an alternate cleaning method will be used.
It is clear that there are critical precautions you must take when working with ozone generators'the dangers of too much ozone exposure are not to be taken lightly. If you are compelled to use an ozone generator for whatever reason, it is crucial that you follow the precautions we listed to ensure your safety.
Moreover it is not advisable to rely heavily on using an ozone generator. Study after study has shown that they are not particularly effective in reducing indoor air concentrations for most VOCs. There are other air purification technologies that are used to help with odor. Our solution, the Molekule PECO air purifier, can destroy VOCs safely and effectively, without the use of any ozone.
Ultimately the choice to use an ozone generator needs to be an informed one, wherein individuals are aware of the risks and know that ozone is not a 'one-size-fits-all' solution.
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There is a large body of written material on ozone and the use of ozone indoors. However, much of this material makes claims or draws conclusions without substantiation and sound science. In developing Ozone Generators that are Sold as Air Cleaners, the 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.
Several brands of ozone generators have EPA establishment number on their packaging. This number helps EPA identify the specific facility that produces the product. The display of this number does not imply EPA endorsement or suggest in any way that EPA has found the product to be either safe or effective.
Please Note: EPA does not certify air cleaning devices. The Agency does not recommend air cleaning devices or manufacturers. If you need information on specific devices or manufacturers, one resource you can consult is the Association of Home Appliance Manufacturers (AHAM), (202) 872-. 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.
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 ; Salls, ; Boeniger, ; American Lung Association, ; Al-Ahmady, ). 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.
Ozone is a molecule composed of three atoms of oxygen. Two atoms of oxygen form the basic oxygen molecule--the oxygen we breathe that is essential to life. The third oxygen atom can detach from the ozone molecule, and re-attach to molecules of other substances, thereby altering their chemical composition. It is this ability to react with other substances that forms the basis of manufacturers' claims.
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. 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, a, b).
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. These exposure limits are summarized in Table 1.
Table 1. Ozone Heath Effects and Standards
Health Effects Risk Factors Health Standards* Potential risk of experiencing: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
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The phrase "good up high - bad nearby" has been used by the U.S. Environmental Protection Agency (EPA) to make the distinction between ozone in the upper and lower atmosphere. Ozone in the upper atmosphere--referred to as "stratospheric ozone"--helps filter out damaging ultraviolet radiation from the sun. Though ozone in the stratosphere is protective, ozone in the atmosphere - which is the air we breathe - can be harmful to the respiratory system. Harmful levels of ozone can be produced by the interaction of sunlight with certain chemicals emitted to the environment (e.g., automobile emissions and chemical emissions of industrial plants). These harmful concentrations of ozone in the atmosphere are often accompanied by high concentrations of other pollutants, including nitrogen dioxide, fine particles and hydrocarbons. Whether pure or mixed with other chemicals, ozone can be harmful to health.
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.
There is evidence to show that at concentrations that do not exceed public health standards, ozone is not effective at removing many odor-causing chemicals.
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.
Results of some controlled studies show that concentrations of ozone considerably higher than these standards are possible even when a user follows the manufacturer's operating instructions.
There are many brands and models of ozone generators on the market. They vary in the amount of ozone they can produce. In many circumstances, the use of an ozone generator may not result in ozone concentrations that exceed public health standards. But many factors affect the indoor concentration of ozone so that under some conditions ozone concentrations may exceed public health standards.
The actual concentration of ozone produced by an ozone generator depends on many factors. Concentrations will be higher if a more powerful device or more than one device is used, if a device is placed in a small space rather than a large space, if interior doors are closed rather than open and, if the room has fewer rather than more materials and furnishings that adsorb or react with ozone and, provided that outdoor concentrations of ozone are low, if there is less rather than more outdoor air ventilation.
The proximity of a person to the ozone generating device can also affect one's exposure. The concentration is highest at the point where the ozone exits from the device, and generally decreases as one moves further away.
Manufacturers and vendors advise users to size the device properly to the space or spaces in which it is used. Unfortunately, some manufacturers' recommendations about appropriate sizes for particular spaces have not been sufficiently precise to guarantee that ozone concentrations will not exceed public health limits. Further, some literature distributed by vendors suggests that users err on the side of operating a more powerful machine than would normally be appropriate for the intended space, the rationale being that the user may move in the future, or may want to use the machine in a larger space later on. Using a more powerful machine increases the risk of excessive ozone exposure.
Ozone generators typically provide a control setting by which the ozone output can be adjusted. The ozone output of these devices is usually not proportional to the control setting. That is, a setting at medium does not necessarily generate an ozone level that is halfway between the levels at low and high. The relationship between the control setting and the output varies considerably among devices, although most appear to elevate the ozone output much more than one would expect as the control setting is increased from low to high. In experiments to date, the high setting in some devices generated 10 times the level obtained at the medium setting (US EPA, ). Manufacturer's instructions on some devices link the control setting to room size and thus indicate what setting is appropriate for different room sizes. However, room size is only one factor affecting ozone levels in the room.
In addition to adjusting the control setting to the size of the room, users have sometimes been advised to lower the ozone setting if they can smell the ozone. Unfortunately, the ability to detect ozone by smell varies considerably from person to person, and one's ability to smell ozone rapidly deteriorates in the presence of ozone. While the smell of ozone may indicate that the concentration is too high, lack of odor does not guarantee that levels are safe.
At least one manufacturer is offering units with an ozone sensor that turns the ozone generator on and off with the intent of maintaining ozone concentrations in the space below health standards. EPA is currently evaluating the effectiveness and reliability of these sensors, and plans to conduct further research to improve society's understanding of ozone chemistry indoors. EPA will report its findings as the results of this research become available.
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, ). 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, a).
The three most common approaches to reducing indoor air pollution, in order of effectiveness, are:
Of the three, the first approach ' source control ' is the most effective. This involves minimizing the use of products and materials that cause indoor pollution, employing good hygiene practices to minimize biological contaminants (including the control of humidity and moisture, and occasional cleaning and disinfection of wet or moist surfaces), and using good housekeeping practices to control particles.
The second approach ' outdoor air ventilation ' is also effective and commonly employed. Ventilation methods include installing an exhaust fan close to the source of contaminants, increasing outdoor air flows in mechanical ventilation systems, and opening windows, especially when pollutant sources are in use.
The third approach ' air cleaning ' is not generally regarded as sufficient in itself, but is sometimes used to supplement source control and ventilation. Air filters, electronic particle air cleaners and ionizers are often used to remove airborne particles, and gas adsorbing material is sometimes used to remove gaseous contaminants when source control and ventilation are inadequate.
See Additional Resources section below for more detailed information about these methods.
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.
See Indoor Air Quality Publications
Publications
California Department of Health Services, Indoor Air Quality Program, DHS-IAQ Program Assistance Line: (510) 620-, Fax: (510) 620-
Federal Trade Commission, Consumer Response Center, (202) 326-.
U.S. Consumer Product Safety Commission,or call Consumer Hotline, English/Spanish: (800) 638-, Hearing/Speech Impaired: (800) .
The Association of Home Appliance Manufacturers (AHAM) has developed an American National Standards Institute (ANSI)-approved standard for portable air cleaners (ANSI/AHAM Standard AC-1-). This standard may be useful in estimating the effectiveness of portable air cleaners. Under this standard, room air cleaner effectiveness is rated by a clean air delivery rate (CADR) for each of three particle types in indoor air: tobacco smoke, dust and pollen. Only a limited number of air cleaners had been certified under this program when this document was written.
A listing of AHAM-certified room air cleaners and their CADRs can be obtained from Aham Verified.
Association of Home Appliance Manufacturers (AHAM)
(202) 872-
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