Ozone treatment & ozone gas hazards home page:

This article series explains the hazards associated with use of ozone gas indoors as a "mold remedy" or as an "air purifier" or as a "mold killing agent".

While there are established uses of ozone in industrial applications and in certain sterilization applications, environmental testing experts and authorities such as the US EPA do not recommend use of ozone for mold treatment.

Use of ozone indoors can be hazardous and can cause oxidation or other adverse reactions with other materials and chemicals indoors.

Ozone Gas Hazards: an Overview of the Hazards of Indoor Ozone Gas

Ozone is widely promoted by ozone generating equipment companies and cleaning services for use in indoor building environments to deodorize, disinfect, "kill" mold, and for "general health".

And while the evidence is that ozone as a mold "treatment" is questionable and while sometimes ozone "mold killing or deodorizing by ozone" causes more problems than it "solves", there are indeed many other appropriate and effective uses of ozone. Indeed dissolved ozone is used in some laundry systems as a disinfectant, typically at levels of 1.5 to 3.0 ppm. [10].

See OZONE AIR PURIFIER WARNINGS

That said, This article describes the dangers of using ozone gas indoors or in vehicles or other enclosed spaces as a deodorant or as a mold treatment.

Other articles in this series give details about ozone gas exposure limits & standards, ozone air purifier warnings, use of ozone as a mold or mold odor treatment, how to test for ozone, ozone toxicity, and authoritative references on the use of ozone in various deodorizing, sterilization and purification applications.

Article Contents

• OZONE HAZARDS
  • OZONE EXPOSURE RISKS Levels for Humans & Other Animals
  • OZONE SMELL DETECTION Can People Smell Ozone?
  • OZONE COMPLAINTS Complaints & Symptoms from ozone in buildings
  • OZONE to KILL MOLD Ozone Generator or Air Purifier to Get Rid of or Kill Toxic Mold Indoors?
  • OZONE to KILL ODORS Air Purifiers to Get Rid of Indoor Odors?
  • OZONE-CREATED PROBLEMS Can Lead to More Odor Problems than Before
  • OZONE CAR DEODORIZING Air Purifiers to Get Rid of Odors in a Car, Truck, Camper, or RV?
  • OZONE EXPOSURE DETECTION in URINE Can we detect dissolved ozone in human urine?

Ozone Exposure Risk Levels for Humans & Other Animals

• Exposure to ozone at a level you can smell or exposure to ozone over long periods at levels greater than 0.05 ppm for 24 hours at a time is likely to be dangerous: [3]
• Health hazards to humans and animals occur and can be severe at ozone levels used for indoor cleaning purposes.
• Details about the allowable exposure limits to ozone are
  
  at OZONE EXPOSURE STANDARDS - separate article

at What Level Can People Smell Ozone?

At least some people can smell levels of ozone down to 0.05 ppm. This odor-detection level is already half-way to the recommended limit. If you are generating ozone indoors, even at "low" levels a problem may be present.

People become desensitized to odors in a short time, perhaps 20 minutes. So if you do not smell it, the ozone level could still be hazardous.

Problems Associated with Ozone Gas Exposure: Complaints & Symptoms

Problems associated with ozone gas exposure include

• Lung irritation and infection. 
• Breathing pain, coughing, wheezing, difficulty when exercising.
• Permanent lung damage.
• Aggravation of pre-existing asthma
• Increased risk of lung illnesses such as bronchitis and pneumonia
• Reduced breathing capacity [4]

...

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2020-10-14 - by (mod) - How to Get Rid of Lingering Odors after an Ozone Treatment of a Building Interior

Ozone

After an ozone generator has been run in a building you won't actually smell ozone itself (O₃) - as that's an extremely volatile gas that quickly dissipates with time and even faster with fresh-air ventilation.

But what can linger, in the worst cases, indefinitely, are odors from other building materials that were oxidized by an over-dose of ozone - the machine was run for too long or at too high an indoor concentration.

Sometimes ventilation can solve the problem, along with time.

But often I find from experience and from a plethora of reader reports, that some oxidized materials such as carpeting, padding, plastics, synthetic fabrics and some other materials will emit an unpleasant (and possibly unhealthy) odor indefinitely. That offgassing is solved, only by removing and replacing the offending source.

6-Step Procedure to get rid of lingering odors and smells after ozone over-treatment of a building interior

1. Try ventilation + fans + heat & sunlight; If ventilation with fresh air, perhaps combined with heat and sunlight to speed offgassing, do not solve the odor problem
2. Find the odord source:
   
   Test various materials and surfaces to be sure you have identified the worst-offenders and odor sources
   
   See SMELL PATCH TEST to FIND ODOR SOURCE
   
   Watch out: Be sure you've followed our suggestions in the smell test procedure including using an independent person or more than one person who have a good sense of smell to evaluate the smell patch test
3. Remove the offending material if it's furnishings or carpeting
4. Clean the exposed hard surfaces
5. Use a sealant?
   
   You may need to use a low VOC or odorless sealant or coating on some surfaces that cannot be easily removed (on occasion readers have traced ozone-after-odors to floors or cabinets or painted surfaces. Those sealants are available in both pigmented and clear forms.
   
   See FUNGICIDAL SPRAY & SEALANT USE GUIDE (it's not just for mold) and
   
   See DISINFECTANTS & SANITIZERS, SOURCES

On 2020-10-14 by Ozone

Ozone was used in my home to get rid of polyurethane fumes. I have been unable to return to my home. The smell from the ozone is so strong that I do not feel well in the house. How do I test for toxicity / safety in my home.

I have read that upholstered items are at most risk. Can you explain and give me any solutions mi have all my windows open and overhead fans running. Nothing seems to work.

On 2019-11-25 by (mod)

Thanks anon; we work hard to provide researched reliable information without conflict of interest, so I'm really grateful when a reader finds it so. Your questions, content criticism, or suggestions also are welcome and helpful.

On 2019-11-24 by Anonymous

Thanks so much. Sorry for the delayed acknowledgement. Always grateful for your input. Has helped enormously on many topics, including reading through your text on various pages along w/Q&A's.

On 2019-11-13 by (mod) - using UV lamps on AC coils in an HVAC system?

UV light has useful applications in some systems but in my view the light is ONLY going to treat surfaces on which it shines. It is not and can not treat airborne contaminants since they don't hang around in moving air through the duct system. And the UV will only treat some (not all) biological contaminants - as we noted

at HVAC SYSTEM ODORS

High levels of ozone are indeed unsafe as you will read in this article series;

However properly adjusted and used there should be NO detectable ozone smell in the air you breathe; if you smell ozone then the system isn't working properly.

On 2019-11-12 by Anonymous

Would you render your opinion about using UV lamps on AC coils in an HVAC system? It's my understanding that ozone is produced when these lamps are in use and I have concerns about the level of ozone produced and health hazards. Thank you, in advance, for your thoughts.

Can I Use an Ozone Generator or Air Purifier to Get Rid of or Kill Toxic Mold Indoors?

Use of ozone to "remove" or "kill" mold is ineffective, not recommended, and may be dangerous. Even if ozone were applied at a concentration and for a duration sufficient to "kill" every mold spore in a building (which is a very dubious claim), depending on the mold genera/species present there is a good chance that the process leaves toxic and allergenic particles in the building.

A "dead" (or non-viable) mold spore may not grow but it can still be a health concern. 

The operative proper word for mold remediation is "clean" or "remove", not "kill." In 1997, Dr. Karin K. Foarde of Research Triangle Institute, tested the ability of ozone to decontaminate fungi on building materials.

At ozone levels of 9 ppm for a 23-hour exposure, ozone was found to be ineffective. [5] (Notice that this is 90-times higher than permitted ozone exposure. Exposure at these "deodorizing" levels would be considered extremely toxic to humans.)

This ozone treatment procedure is not recommended b

y the NY City Department of Health Guidelines on the Assessment and Remediation of Fungi in Indoor Environments. Jim Holland's article on Ozone as a "mold remediation step" is available online [6] and is a good summary of this point. Jack E. Peterson's 1987 excellent work "Health Hazards of some Gases" also addresses ozone hazards but it may be harder to find so I have quoted from it at the end of this paper.

Deodorization and cleaning claims are questionable: The apparent deodorization at high ozone levels may be simply the effect of a general desensitization to odors in the nose of building occupants rather than actual removal of an odor source. Ozone has been used following building fires to "reduce" smoke odors but even in this application it does not remove soot.

Can I Use Ozone or Ozone-Based Air Purifiers to Get Rid of Indoor Odors?

The answer is, maybe.

If, for example, there is a persistent odor source (

such as a dead animal, flood damage, mold in building wall and ceiling cavities), no amount of "air treatment" of any kind will remove the problem source. There is no substitute for the actual physical effort to find and remove the offending source. C

leaning or removing the problem source is proper and effective. Professional use of ozone, at concentrations and durations which the applicator guarantees will not damage building materials or cause other outgassing, may be helpful as one step in a cleaning procedure where mold is not involved.

Ozone has been used successfully in water treatment and in disinfection of cooling towers and possibly wastewater. However it is not a durable, reliable treatment in that O3 molecules are highly reactive and volatile and thus treated substances do not remain so.

Use of ozone may oxidize and damage materials and increase odor levels: [7]

If ozone is no longer being generated in a building the presence of ozone will diminish quite rapidly. However, other odors may remain or may even be increased.

Under What Circumstances Can Use of Ozone Indoors Lead to More Odor Problems than Before?

Because ozone is a very powerful oxidant,

it may react with (oxidize) many materials found indoors, including carpets, carpet padding (especially rubber), other floor coverings, furniture, furniture cushion foam, and even surface paints and finishes.

A common example is ozone-oxidized rubber carpet backing or padding. We gather from research and other studies indicate that any material that will oxidize may be expected to react with ozone, especially cross-linked organic molecules, especially rubber.

Use of ozone may produce dangerous airborne byproducts: In other words, attempts to use high levels of ozone to "clean" or "deodorize" building interiors may in fact generate a second generation of unpleasant and even dangerous outgassing which may remain, persistent indoors, after the ozone "treatment." Examples include increased levels of indoor formaldehyde, formic acid and other acid gases, toluene, or other toxic chemicals.

Use of ozone may increase sub micron particulates: Attempts to use high levels of ozone to "clean" or "deodorize" building interiors may also increase the level of extremely small sub-micron particles which themselves can be severe respiratory irritants.

Quoting and/or paraphrasing further from "Ozone-Generating Air Cleaners and Indoor Air Chemistry" in the REFERENCES section at theend of this document:

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.

• In one study (Shaughnessy and Oatman, 1991), a large ozone generator recommended by the manufacturer for spaces "up to 3,000 square feet," was placed in a 350 square foot room and run at a high setting. The ozone in the room quickly reached concentrations that were exceptionally high--0.50 to 0.80 ppm which is 5-10 times higher than public health limits.
• In an EPA study, several different devices were placed in a home environment, in various rooms, with doors alternately opened and closed, and with the central ventilation system fan alternately turned on and off. The results showed that some ozone generators, when run at a high setting with interior doors closed, would frequently produce concentrations of 0.20 - 0.30 ppm. A powerful unit set on high with the interior doors opened achieved values of 0.12 to 0.20 ppm in adjacent rooms. When units were not run on high, and interior doors were open, concentrations generally did not exceed public health standards (US EPA, 1995).
• The concentrations reported above were adjusted to exclude that portion of the ozone concentration brought in from the outdoors. Indoor concentrations of ozone brought in from outside are typically 0.01- 0.02 ppm, but could be as high as 0.03 - 0.05 ppm (Hayes, 1991; U.S. EPA, 1996b; Weschler et al., 1989, 1996; Zhang and Lioy; 1994). If the outdoor portion of ozone were included in the indoor concentrations reported above, the concentrations inside would have been correspondingly higher, increasing the risk of excessive ozone exposure.
  
• None of the studies reported above involved the simultaneous use of more than one device. The simultaneous use of multiple devices increases the total ozone output and therefore greatly increases the risk of excessive ozone exposure.

Watch out: improper use of ozone indoors may oxidize certain plastics, leading to dangerous formation of oxides of nitrogen gases. See Nitrogen Oxides Gas for details.

Can I use Ozone or Ozone-Based Air Purifiers to Get Rid of Odors in a Car, Truck, Camper, or RV?

The answer is, maybe.

The same worries pertain about use of ozone inside vehicles as we discussed above concerning the use or over-use of ozone as an "odor killer" inside buildings. But the risks of overdoing ozone inside of a car or vehicle may be still greater for two reasons:

Using an ozone generator inside of the much smaller space of a vehicle can expose the vehicle's interior to higher ozone concentrations, leading to higher risk of over-dosing with ozone, and oxidized materials.

Most vehicles and campers use a greater quantity of plastics and synthetic materials than may be found in most buildings. So the risk of oxidizing plastic materials may be greater.

Please see our full article about odors in cars and other vehicles, found

at BOAT & CAR SMELLS & ODORS.

Watch out: as we warned earlier, improper use of ozone indoors may oxidize certain plastics, leading to dangerous formation of oxides of nitrogen gases. See Nitrogen Oxides Gas for details.

Question: The Excretion of dissolved ozone in human urine?

After breathing a high dose of Ozone, is it possible to absorb it and urinate it out? As after breathing it in at my workplace, I believe I could smell it in my urine. - Anthony

Reply:

Ozone can indeed become dissolved in the human bloodstream, and Velio A Bocci et als point out that while there are effective medical uses for inhaled ozone when applied in a medically supervised [oxygen] gas mixture use, ozone may be "toxic for the pulmonary system during prolonged inhalation, continuing ... when it is chronically inhaled, [ozone] is highly toxic for the pulmonary system because the enormous alveolar surface, unprotected by sufficient antioxidants, is exposed to the cumulative ozone dose, which causes a chronic inflammation." [11].

As for ozone being dissolved in urine, presumably removed from blood and excreted through the kidneys, the same authors point out risks of kidney damage from ozone. But we have not found an authoritative source indicating the olfactory detection of ozone in human urine and we suspect that the ozone level would have to be very high, probably dangerously so, for that to be the case. [Queries for citations for this point are pending - [11] - Ed.]

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Continue reading at OZONE AIR PURIFIER WARNINGS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see OZONE HAZARD FAQS - Questions & answers about dangers of ozone tools, exposure, etc. posted originally at this page.

Or see these

Recommended Articles

• DISINFECTANTS & SANITIZERS, SOURCES
• OZONE HAZARDS - home
  • OZONE AIR PURIFIER WARNINGS
  • OZONE EXPOSURE STANDARDS
  • OZONE GAS EXPOSURE EFFECTS
  • OZONE GAS PROPERTIES
  • OZONE GAS EXPOSURE LIMITS - EPA
  • OZONE GENERATOR EFFECTIVENESS for INDOOR AIR POLLUTION
  • OZONE HAZARDS
  • OZONE in HOT TUBS, SPAS, POOLS
  • OZONE MOLD KILL TREATMENT
  • OZONE MOLD / ODOR TREATMENT WARNINGS
  • OZONE MSDS [PDF]
  • OZONE REFERENCES & OZONE GENERATOR INSTRUCTIONS
  • OZONE SHOCK TREATMENTS NOT RECOMMENDED
  • OZONE TREATMENT TIME RECOMMENDATIONS
  • OZONE TESTS
  • OZONE TOXICITY
  • OZONE for WATER DISINFECTION
  • RELYING on OZONE to KILL MOLD
  • XENON LAMP OZONE OUTPUT?
• SMELL PATCH TEST to FIND ODOR SOURCE

Suggested citation for this web page

OZONE HAZARDS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING ODOR DIAGNOSIS & CURE

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Citations & References

In addition to any citations in the article above, a full list is available on request.

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