Ozone air treatment, shock treatments, and overdosing warnings:

Ozone has been widely used as a disinfection method for more than 100 years and has applications ranging from hospital disinfection to water treatment. However if ozone treatments are not properly matched to the application the results can be both ineffective and potentially harmful.

This article provides government and other authoritative warnings about using ozone generators and ozone air purifiers in buildings to "purify" indoor air or to "kill mold" in buildings.

We give a definition of ozone or O₃, we explain what problems can arise when using ozone generators to try to get rid of odors indoors or to try to kill mold.

We explain the problem of oxidation of building materials from excessive ozone exposure and the horrible chemical smells that may follow such mistakes. We describe how to track down which building materials were over-dosed with ozone and are now giving off a new stink, and we explain how to cure that problem. (Note: other uses of ozone as a disinfectant can be effective and are important in many applications.)

Warnings About Using Ozone for Treatment of Indoor Air: Respiratory System

General Use of Ozone Generators nor Ozone Shock Treatments as a "Cure" for Building Mold or Odors is Not Recommended

Watch out:  Ozone is a highly toxic, oxidizing gas. It can be absorbed into the body via inhalation, skin or the eyes. It can also oxidize building materials. See the Ozone hazard and use warning articles listed at the end of this article.

Watch out: In-Home or "portable" ozone generators and industrial or "shock treatment" ozone generators not only fail to find and remove the source of mold or building odors, in addition ozone concentrations generated by ionic air purifiers can exceed (industrial) levels permitted by U.S. Environmental Protection Agency. This problem is more severe when

• an ozone generator is used in a small, enclosed space such as an individual room or in an automobile.
  
  See OZONE to Get Rid of Odors in a Car
• an ozone generator is used in a poorly ventilated building
• an ozone generator is used in an enclosed space for too long a time or at too high a concentration
• ozone "shock treatments" recommended by some cleaning companies can generate nearly 1000 times the level of indoor ozone inside a building, leading to severe health hazards if anyone is in the structure and leading to oxidation of building materials that in turn produce worse odors than before, ultimately leading to a need for further demolition and removal of oxidized materials

In addition, a ban of in-home ozone producing air purifiers was announced by the California Air Resources Board in September 2007. This law requires testing and certification of all types of air purifiers to verify that they do not generate excessive ozone.

See "HEALTH HAZARDS of Ozone-generating Air Cleaning Devices", [PDF] State of California-Health and Welfare Agency, Department of Health Services, Indoor Air Quality Section

Research on Secondary Chemical-like Building Odors Following Over-Use of Ozone Generators in Buildings

Scholarly research cited here confirms our opinion that ozone treatments, particularly where over-exposed in buildings, vehicles or other enclosed spaces can create both health hazards to occupants and secondary chemical-like odors from the reaction of ozone with various furnishings, coatings, or other materials in buildings.

Reserarch is suggestive of the relationship between ozone treatments and both a preceived reduction in odors and (when over-used) the production of new "chemical-like" odors in buildings.

• Also see OZONE REFERENCES & OZONE GENERATOR INSTRUCTIONS
• Boeniger, Mark F. "Use of ozone generating devices to improve indoor air quality." American Industrial Hygiene Association 56, no. 6 (1995): 590-598.
  
  Abstract: Room ozonization has been in widespread use to “freshen” indoor air for more than 100 years. This use is sometimes promoted with the claim that ozone can oxidize airborne gases, and even particulates, to simple carbon dioxide and water vapor.
  
  Aside from whether ozone can improve indoor air quality, the potentially deleterious consequences to public health of overexposure to ozone are of concern.
  
  The literature on both allegations is reviewed. It indicates that ozone is not a practical and effective means of improving indoor air quality, especially in light of its potentially serious risk to health.
• Sarwar, Golam, and Richard Corsi. "The effects of ozone/limonene reactions on indoor secondary organic aerosols." Atmospheric Environment 41, no. 5 (2007): 959-973.
• Knudsen, Henrik Nellemose, P. A. Nielsen, P. A. Clausen, C. K. Wilkins, and P. Wolkoff. "Sensory evaluation of emissions from selected building products exposed to ozone." Indoor Air 13, no. 3 (2003): 223-231.
• Bernstein, Jonathan A., Neil Alexis, Hyacinth Bacchus, I. Leonard Bernstein, Pat Fritz, Elliot Horner, Ning Li et al. "The health effects of nonindustrial indoor air pollution." Journal of Allergy and Clinical Immunology 121, no. 3 (2008): 585-591.
• CLAUSEN, PA, C. K. Wilkins, and G. D. Nielsen. "Formation of strong airway irritants in terpene/ozone mixtures." Indoor air 10, no. 2 (2000): 82-91.
  
  The paper demonstrates that airway irritants can be formed by reactions of ozone and unsaturated volatile organic compounds.
  
  Practical guidelines resulting from these studies await additional research results.
  
  However, in the interim, it appears prudent to limit concentrations of ozone and certain reactive volatile organic compounds, especially, pine and citrus oils (e.g., in cleaning agents) in the indoor air.
  
  This requires appropriate maintenance of devices that generate ozone, e.g. photocopiers, supplying exhaust ventilation to areas in which ozone sources are located, and especially discouraging use of ozone generators as devices to remove odors from the indoor air.
• Fiedler, Nancy, Robert Laumbach, Kathie Kelly-McNeil, Paul Lioy, Zhi-Hua Fan, Junfeng Zhang, John Ottenweller, Pamela Ohman-Strickland, and Howard Kipen. "Health effects of a mixture of indoor air volatile organics, their ozone oxidation products, and stress." Environmental health perspectives (2005): 1542-1548.
  
  This study looked at ozone O3 + VOCs exposure and found that in that combination other factors were more significant.
• Hubbard, H. F., B. K. Coleman, G. Sarwar, and R. L. Corsi. "Effects of an ozone‐generating air purifier on indoor secondary particles in three residential dwellings." Indoor air 15, no. 6 (2005): 432-444.
  This study found that
  
  "... 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 atmospheres. Human exposure to secondary organic particles can be reduced by minimizing the intentional release of ozone, particularly in the presence of high terpene sources. "
• Klenø, Jacob G., Per A. Clausen, Charles J. Weschler, and Peder Wolkoff. "Determination of ozone removal rates by selected building products using the FLEC emission cell." Environmental science & technology 35, no. 12 (2001): 2548-2553.
  Discusses the "ozone removal rate" by other building products.
  Abstract:
  
  Ozone removal by 16 aged (older than 1−120 months) but unused building products or materials was studied in a test system that included the field and laboratory emission cell (FLEC).
  
  The ozone removal was studied at 50 ± 1 ppb ozone, a relative humidity of 50 ± 5%, a temperature of 21 ± 2 °C, and an air flow rate of 900 ± 10 mL min-1 through the FLEC (air velocity ca. 3 cm s-1).
  
  The ozone removal increased rapidly during the first 1−2 min and either remained at a constant level or decreased asymptotically to reach a steady state-like value. The ozone removal profiles for a given material showed good repeatability during replicate experiments. Ozone deposition velocities for the building products were calculated to be between 0.0007 cm s-1 (lacquered ash) and 0.8 cm s-1 (unpainted gypsum board).
• Laumbach, Robert J., Nancy Fiedler, Carol R. Gardner, Debra L. Laskin, Zhi-Hua Fan, Junfeng Zhang, Charles J. Weschler et al. "Nasal effects of a mixture of volatile organic compounds and their ozone oxidation products." Journal of occupational and environmental medicine 47, no. 11 (2005): 1182-1189.
  Abstract:
  
  Objective: Our objective was to determine if low levels of a mixture of volatile organic compounds (VOCs) and their ozone (O3) oxidation products, similar to what might be found in “sick buildings,” cause nasal irritation and inflammation under controlled exposure conditions.
  
  Methods: Healthy, nonsmoking women (n = 130) completed 2-hour controlled exposures to VOCs, VOCs and O3, and a masked air “MA” control in random order at least 1 week apart. VOCs and O3 concentrations were approximately 25 mg/m3 and approximately 40 ppb, respectively.
  
  Nasal symptoms were rated before, during, and after exposure. Nasal lavage fluid was analyzed for polymorphonuclear cells, total protein, interleukin-6, and interleukin-8. Results: We found no significant differences in symptoms or markers of nasal inflammation between exposure conditions. Conclusions: Results suggest that VOCs and their oxidation products may not cause acute nasal effects at low concentrations.
• Wolkoff, P., C. K. Wilkins, P. A. Clausen, and G. D. Nielsen. "Organic compounds in office environments–sensory irritation, odor, measurements and the role of reactive chemistry." Indoor air 16, no. 1 (2006): 7-19.
  This study notes that ozone O3 - Alkene oxidation effects are important - this is also my hypothesis about why ozone creates secondary odor problems in buildings when over-used. O3 is a highly reactive molecule.
• Uhde, E., and T. Salthammer. "Impact of reaction products from building materials and furnishings on indoor air quality—a review of recent advances in indoor chemistry." Atmospheric Environment 41, no. 15 (2007): 3111-3128.
  Abstract
  
  The variety of chemical substances present in modern building products, household products and furnishings provides potential for chemical reactions in the material (case 1), on the material surface (case 2) and in the gas phase (case 3).
  
  Such “indoor chemistry” is known as one of the main reasons for primary and secondary emissions. The conditions of production often cause unwanted side reactions and a number of new compounds can be found in finished products. Elevated temperatures are responsible for the degradation of cellulose, decomposition of non-heat-resistant additives and other thermally induced reactions like Diels–Alder synthesis. Heterogeneous chemistry takes place on the surface of materials.
  
  Well-known examples are the formation of aliphatic aldehydes from the oxidation of unsaturated fatty acids or the cleavage of photoinitiators under the influence of light. In case of composite flooring structures hydrolysis is one of the major pathways for the appearance of alcohols from esters. If different kinds of material are fixed together, emissions of new VOCs formed by inter-species reactions are possible.
  
  Other indoor air pollutants are formed by rearrangement of cleavage products or by metabolism. Compounds with –Cdouble bond; length as m-dashC– bonds like terpenes, styrene, 4-phenylcyclohexene, etc. undergo gas phase reactions with O3, NOx, OH and other reactive gases.
  
  It has been shown that such products derived from indoor-related reactions may have a negative impact on indoor air quality due to their low odor threshold or health-related properties.
  
  Therefore, the understanding of primary and secondary emissions and the chemical processes behind is essential for the evaluation of indoor air quality. This publication gives an overview on the current state of research and new findings regarding primary and secondary emissions from building products and furnishings.
• Wainman, Thomas, Junfeng Zhang, Charles J. Weschler, and Paul J. Lioy. "Ozone and limonene in indoor air: a source of submicron particle exposure." Environmental Health Perspectives 108, no. 12 (2000): 1139.
  
  Abstract: Little information currently exists regarding the occurrence of secondary organic aerosol formation in indoor air.
  
  Smog chamber studies have demonstrated that high aerosol yields result from the reaction of ozone with terpenes, both of which commonly occur in indoor air. However, smog chambers are typically static systems, whereas indoor environments are dynamic. We conducted a series of experiments to investigate the potential for secondary aerosol in indoor air as a result of the reaction of ozone with d-limonene, a compound commonly used in air fresheners.
  
  A dynamic chamber design was used in which a smaller chamber was nested inside a larger one, with air exchange occurring between the two. The inner chamber was used to represent a model indoor environment and was operated at an air exchange rate below 1 exchange/hr, while the outer chamber was operated at a high air exchange rate of approximately 45 exchanges/hr.
  
  Limonene was introduced into the inner chamber either by the evaporation of reagent-grade d-limonene or by inserting a lemon-scented, solid air freshener.
  
  A series of ozone injections were made into the inner chamber during the course of each experiment, and an optical particle counter was used to measure the particle concentration. Measurable particle formation and growth occurred almost exclusively in the 0.1-0.2 microm and 0.2-0.3 microm size fractions in all of the experiments.
  
  Particle formation in the 0.1-0.2 microm size range occurred as soon as ozone was introduced, but the formation of particles in the 0.2-0.3 microm size range did not occur until at least the second ozone injection occurred.
  
  The results of this study show a clear potential for significant particle concentrations to be produced in indoor environments as a result of secondary particle formation via the ozone-limonene reaction. Because people spend the majority of their time indoors, secondary particles formed in indoor environments may make a significant contribution to overall particle exposure.
  
  This study provides data for assessing the impact of outdoor ozone on indoor particles. This is important to determine the efficacy of the mass-based particulate matter standards in protecting public health because the indoor secondary particles can vary coincidently with the variations of outdoor fine particles in summer.
• Weschler, Charles J., and Helen C. Shields. "Indoor ozone/terpene reactions as a source of indoor particles." Atmospheric Environment 33, no. 15 (1999): 2301-2312.
  Abstract
  
  This paper reports effects of reactions between ozone and selected terpenes on the concentrations and size distributions of airborne particles in a typical indoor setting.
  
  The studies were conducted in adjacent, identical offices. In the first set of experiments, known concentrations of ozone and a selected terpene (either d-limonene, α-terpinene, or a terpene-based cleaner whose major constituent is α-pinene) were deliberately introduced into one of the offices while the other office served as a control. Subsequent particle formation and redistribution were monitored with an eight-channel optical particle counter.
  
  Particle formation was observed in each terpene system, but was greatest in the case of d-limonene. The number of particles in the 0.1–0.2 μm diameter size range was as much as 20 times larger in the office with deliberately supplemented ozone and d-limonene than in the office serving as the control.
  
  The concentration differences in the larger size ranges developed with time, indicating the importance of coagulation and condensation processes in this indoor environment. In the second set of experiments, d-limonene was deliberately introduced into one of the offices, but ozone was not supplemented in either office; instead, the indoor ozone concentrations were those that happened to be present (primarily as a consequence of outdoor-to-indoor transport).
  
  In the office that contained supplemental d-limonene, the concentrations of the 0.1–0.2 μm particles tracked those of indoor ozone (the limiting reagent) and were as much as 10 times greater than levels measured in the comparable office that did not contain supplemental d-limonene.
  
  The results demonstrate that ozone/terpene reactions can be a significant source of sub-micron particles in indoor settings, and further illustrate the potential for reactions among commonly occurring indoor pollutants to markedly influence indoor environments.
• Wolkoff, Peder. "Impact of air velocity, temperature, humidity, and air on long-term VOC emissions from building products." Atmospheric Environment 32, no. 14 (1998): 2659-2668.
  Abstract
  
  The emissions of two volatile organic compounds (VOCs) of concern from five building products (BPs) were measured in the field and laboratory emission cell (FLEC) up to 250 d.
  
  The BPs (VOCs selected on the basis of abundance and low human odor thresholds) were: nylon carpet with latex backing (2-ethylhexanol, 4-phenylcyclohexene), PVC flooring (2-ethylhexanol, phenol), floor varnish on pretreated beechwood parquet (butyl acetate, N-methylpyrrolidone), sealant (hexane, dimethyloctanols), and waterborne wall paint on gypsum board (1,2-propandiol, Texanol).
  
  Ten different climate conditions were tested: four different air velocities from ca. 1 cm s-1 to ca. 9 cm s-1, three different temperatures (23, 35, and 60°C), two different relative humidities (0% and 50% RH), and pure nitrogen instead of clean air supply.
  
  Additionally, two sample specimen and two different batches were compared for repeatability and homogeneity. The VOCs were sampled on Tenax TA and determined by thermal desorption and gas chromatography (FID).
  
  Quantification was carried out by individual calibration of each VOC of concern. Concentration/time profiles of the selected VOCs (i.e. their concentration decay curves over time) in a standard room were used for comparison. Primary source emissions were not affected by the air velocity after a few days to any great extent.
  
  Both the temperature and relative humidity affected the emission rates, but depended strongly on the type of BP and type of VOC. Secondary (oxidative) source emissions were only observed for the PVC and for dimethyloctanols from the sealant. The time to reach a given concentration (emission rate) appears to be a good approach for future interlaboratory comparisons of BP’s VOC emissions.

Remember that indoor temperature and humidity are important factors.

Although it was not focused on the oxidation effects of ozone on polyurethane coatings, there has been some research that confirms that polyurethane, the presumed coating on some wood floors, can be affected by ozone exposure. Other older floor coatings such as varnish or stain may also be affected by ozone treatments.

• Yuan, Youling, Fei Ai, Xiaopeng Zang, Wei Zhuang, Jian Shen, and Sicong Lin. "Polyurethane vascular catheter surface grafted with zwitterionic sulfobetaine monomer activated by ozone." Colloids and Surfaces B: Biointerfaces 35, no. 1 (2004): 1-5.
• Ko, Young Gun, Young Ha Kim, Ki Dong Park, Hee Jung Lee, Won Kyu Lee, Hyung Dal Park, Soo Hyun Kim, Gil Sun Lee, and Dong June Ahn. "Immobilization of poly (ethylene glycol) or its sulfonate onto polymer surfaces by ozone oxidation." Biomaterials 22, no. 15 (2001): 2115-2123.

Ozone as Possible By-Product of Xenon Light Disinfection

This discussion has moved to a separate article. Please see XENON LAMP OZONE OUTPUT?

 

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Question: Ozone shock treatment left strong electrical / chemical odor & many questions

I am hoping you can help me with my problem. I am quite desperate because there is little information to be found on the topic, and most people I contacted have never heard of my problem. Here is what happened:

A few days ago I had an ozone shock treatment done in one room of my apartment. I was gone during the process but when I returned I noticed a very strong electrical/chemical odor. The odor is concentrated in the room I had the treatment done but some of it can be smelled in other rooms.

I opened all windows for about 4 hours with little success. After a while my airways started to become irritated, and I left the home to stay with family. I spoke to the contractor who did the shock treatment, and he told me he left the machine inside the small room for 20 hours, which seems excessive to me.

I also think the room was not aired out until I returned to the home, which was 24 hours after the machine was removed. I read on your website that overdosing can cause furniture to oxidize, producing harmful chemicals.

Now I have the following concerns and questions[ about the ozone treastment that was performed]

• How do I get these chemicals out of my house? Will washing or steam cleaning fabrics, and wiping surfaces remove a sufficient amount? Or do I most likely need to replace furniture and move out? I read about the sniff test you recommended but I am concerned about directly inhaling the chemicals.
• Are there options to have the place professionally cleaned to remove the chemicals?
• Are the chemicals being continuously being released into the house, causing toxic indoor air?
• Since it was used so excessively, could some of the ozone have still been there when I came home and is that possibly what I smelled?
• Is it at all safe to return to and stay in the home as long as I still notice a smell?

I am not too concerned about the odor itself, but rather about my health. I am currently 23 weeks pregnant and I want to make sure that my home is safe for me and my baby to live in. I am sincerely hoping you can help me because I don't know of many resources I could contact about this. - S.O.

Reply: outgassing from oxidized plastics, synthetics, coatings, and some other materials might be harmful following an over-treastment by ozone indoors

S.O.,
I hate to give an answer that is easy for me and hard or costly for you, but pregnant .... I would prefer you stayed out of the environment untilthe odors and issues are removed. Check with your doctor and let us know what she or he says.

I want to add that the hazard would not be from ozone - which is long gone, but there could be toxic as well as irritating gases, possibly particles,in the environment, depending on the extent of oxidation that took place

Reader Follow-up: should I do air testing for ozone?

Thank you very much for your prompt answer! I am so grateful that you take the time to answer my questions.

I did see a doctor right after I left because I experienced some airway irritation. He said it was good I left but he could not answer any of my questions regarding the chemicals, neither could the poison control center. After reading the article and your advice, I have a few questions left:

Once I have found the items that have been oxidized, do they have to be replaced in all instances, or can cleaning them (wiping, vacuuming, steam cleaning) take care of the problem? Again, I want to be sure it’s 100% safe for me and my child to be around these items. If we have to move and replace some of the furniture in the room, then so be it.

If an item in the room has no smell to it (as determined by the sniff patch test), does that mean it is not contaminated with harmful chemicals or was not affected by the oxidation?

Do you recommend air quality testing?

Once again, thank you for helping me with my problem! It’s been quite stressful trying to figure out what to do or who to contact. Nobody seems to ever have heard of a case like mine.

Reply: no

Cleaning can sometimes help on hard surfaces but if you find that carpet padding, foam cushions, etc. are oxidized and smelling, they usually have to be replaced.

Perhaps you want to try to find what smells, remove or replace it, see what's left, before hiring an expert. The cost of bringing in someone who is actually competent is probably more than $1000 - you might spend that money on cleanup first. Beware of people who just stop by to collect a test - not diagnostic so not really helpful enough. Even if such a test indicates there's a problem you still won't know what it is.

Reader Follow-up: are items that don't smell therefore safe?

Your answers have been very helpful! I have one more question though: If an item has no smell to it, does that mean it is free from toxic particles and safe to be around?

Reply: who knows? probably not.

Your question is a bit too broad to make a promise but it's reasonable to suppose that if an object or material did not develop an odor from the ozone treatment it was probably not significantly oxidized.

Reader Follow-Up: I washed my clothes, now they smell different, are they harmful?

Alright, this should be my last question: I washed some of my clothes that have been exposed.The initial bad smell came out, however, I noticed that these clothes now smell a bit different from the clothes that have not been exposed. It is a normal clothes / fresh laundry smell and I only noticed a difference by directly comparing them. I assume they smell different because the chemical make-up of the fabric has somewhat been changed. Now, could it be harmful to wear these clothes? Once again, thank you very much!

Reply: balance the cost of worry against the cost of testing against the cost of replacement of things that worry you

I am doubtful that there is any easy, credible, inexpensive answer to the question you pose. I am doubtful that we can even assert that the odor change you report is due to ozone treatment, though I imagine that is a possibility.

To perform a detailed comparative analysis on two fabric samples to study their chemical makeup and chemical modification before and after ozone treatment, then cleaning, with possible effects of cleaners, laundry soaps, etc., I think you'd need two to four FLIR spectographic analyses done at about $1200. each.

To me that makes just no sense whatsoever. Worry itself has a health cost. If you are worried about these things in my OPINION it would be most economical to throw them away.

 

Comment: ozone shock treatment done for smoke odor problem - now a burnt smell remains

(Apr 25, 2016) Robert said:

I had a smoke odor problem in garage that wouldn't go away after weeks of airing area. Local restoration company recommended ozone shock treatment for a minimum of 24 hour

Garage was detached from house but ozone odor (which is almost as offensive to me as smoke) permeated my entire house.

Now I have a smell(sweet,acidic,burnt electronics) that has affected all of my possession: clothes, furniture, pictures, CD's and videos, counter tops, media equipment, everything.

A few things can be salvaged by washing but basically the ozone smell is the most resilient and pervasive I have ever experienced. For me, ozone treatment was a huge mistake and I would never recommend to anyone.

...

Continue reading at OZONE TREATMENT TIME RECOMMENDATIONS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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