Toxicity of ozone gas:

Is an indoor ozone generator harmful to family or pets? Properties and Actual Ozone Output of the OZN-jr ozone generator. What is the Legal Definition of "Up To" in Advertising Claims? What is the toxicity of Ozone Gas?

This article discusses the toxicity of ozone gas in buildings, providing a summary of the hazards of indoor ozone levels & indoor ozone generators as well as the use of ozone generators for "mold remediation" - a popular but quite doubtful mold remedy.

Ozone Toxicity Levels: How toxic is ozone, general background, levels of ozone gas toxicity, ozone gas applications

While there are some important uses of ozone (such as for medical disinfection under controlled conditions), in general this is an idea which ranges from possibly helpful to rather bad to dangerous in the home.

This article explains the effects of using ozone in buildings for these purposes and warns consumers about misapplication of and health risks from ozone in buildings.

Because at least some of these claims are based on marketing desire, not good science, and because ozone exposure can be both dangerous and ineffective indoors, we have collected some information and references on this topic.

Photo: a demonstration of ozone production by E.H. Johnston at the Fixed Nitrogen Research Laboratory in 1926, wikipedia.org commons. [Click to enlarge any image]

Article Contents

• OZONE TOXICITY
  • ARE OZONE GENERATORS HARMFUL to PEOPLE or PETS?
  • PROPERTIES & ACTUAL OZONE OUTPUT - OZN-jr OZONE GENERATOR
  • LEGAL DEFINITION of "UP TO" in ADVERTISING CLAIMS
  • TOXICITY of OZONE GAS
  • HEALTH EFFECTS of OZONE EXPOSURE

Is an indoor ozone generator harmful to family or pets?

Anonymous asked: A friend of ours gave us a ozone junior™ to use in our home it comes on for 10 minutes off for 10 minutes.

We are happy with it as far as taking care of the pet odors or any odors but are concerned on whether it is safe to use as it had no paper work. I would just like to know whether this can be harmful to my family or pets? - N.A.

(Feb 17, 2015) Derik said:

Please evaluate the claims by Forever Ozone™ also selling on Amazon: 7000mg/hour (7g/hr). They use a 100 sq ft room.

Reply: It depends ... 

It might be. A competent onsite inspection or testing by an expert might find other unsafe conditions in your home or conditions that are affecting how your ozone air machine performs.

If there is a hazard to humans or other animals from using an ozone generator indoors (or in a vehicle) it will depend on at least the following

• The level of or concentration of ozone reached in the occupied space
  
  Watch out: Even very low concentrations of ozone can be harmful to the upper respiratory tract and the lungs.
  
  The severity of injury depends on both by the concentration of ozone and the duration of exposure. Severe and permanent lung injury or death could result from even a very short-term exposure to relatively low concentrations. - Canadian Centre for Occupational Health and Safety cited at OZONE TOXICITY RESEARCH
• The duration of exposure of the occupants to the ozone
• The physical condition and perhaps age, size and other aspects of the occupants, humans, or animals as well as other metabolites or other contaminants that might be present in their lungs
• The presence of other materials that might be oxidized and off-gas during the ozone treatment and the hazards of those gases

Ozone generators designed for use in buildings, for example to remove smoke particles and odors, can generate high levels of ozone, as much as 3 grams per hour.

Just what concentration of ozone will be created in indoor air by an ozone generator depends on a number of variables including the

• ozone generator's output, and the method being used to generate ozone (UV light, corona discharge)
• the size of the space,
• the degree to which the treated space is enclosed or
• the amount of fresh air entering the space,
• the indoor temperature,
• the indoor relative humidity, and
• other conditions.

How to Avoid an Ozone Overdose

That said, here are some things to consider when asking whether or not a particular use of an ozone generator indoors is helpful or harmful:

• Read the ozone generator's instructions: Start by making sure you are using the equipment according to the manufacturer's instructions.
• Do not over-dose the area: Warnings about ozone gas itself are at OZONE HAZARDS and
  
  caveats about residential or in-home ozone "air purifiers" are
  
  at OZONE AIR PURIFIER WARNINGS.
  
  Beginning just below, we discuss actual ozone gas toxicity - harmful levels.
  
  Also see OZONE MSDS.
  
  Also you can read about the actual OZONE EXPOSURE STANDARDS but without expert testing in your own home you may have no idea how your home's ozone level compares with the standards.
• Watch out for an ozone odor: Our opinion is that as a very crude rule of thumb, if you smell ozone or the air has a funny "electric" smell, that is if there is a detectable ozone odor, the equipment is probably not operating safely or correctly.
• Watch the time: of more than a thousand consumer complaints we have received about problems following ozone treatments and that cite permanent damage to components inside of a building or inside of a car, truck, boat or airplane when there was an apparent overdose or over-use of an ozone generator, often the equipment was left on and operating for many hours, sometimes days, in a misguided effort to "kill mold" or "kill a fireplace smell".
  
  The result can be oxidized building materials, carpets, etc. that have to be discarded.
• Check with the manufacturer: Other than that crude measure, you'd have to either rely on the manufacture's quality control and on following the product instructions, or you'd need to make actual ozone level measurements in the building where the equipment is used.
• Measure the actual ozone level? During ozone generation we can measure and have measured ozone gas levels (when we were convinced there was a reason to do so) using a gas measurement pump and tube system such as that described
  
  at USE of a DRAGER GAS TESTING PUMP.
  
  But generally attempts to measure ozone levels is not going to be useful in addressing a lingering or new building odor or chemical smell or health complaint that is lodged after the ozone generator has been used: ozone is very volatile. It's gone. Trying to measure the hands of height of your horse after it has run out the barn door and escaped to visit a neighbour is not going to be easy.

Properties and Actual Ozone Output of the OZN-jr™ ozone generator

Reader Questions about ozone generators & their output:

Derik & Anon: here is an example calculation in which we show how you can calculate the cubic feet in a room and the ozone output of an ozone generator to obtain the actual ozone concentration in that space, assuming that the space is closed and air-tight. Certainly with doors or windows open or drafts the effects of the ozone generator will be different (and probably reduced).

Information about your "ozone junior" ozone generator: IF you are referring to the OZN-jr Ozone Generator that we noted is for sale at Amazon.com. An Amazon advertisement viewed in March 2011 indicated that the OZN-jr ozone generator unit produces 200 mg of ozone per hour.

The advertising material asserts that the product is "good for deodorizing up to 1000 cubic feet."

The product manufacturer, Sunlight Solutions (seeReferences or Citations ), indicates that "Ozone output is 8 mg/hr."

How big is a 1000 cubic foot room? Figuring an 8-foot ceiling, that's about 125 square feet, or a 10 x 12 room.

Calculating ozone generator output concentration in a room: How much is 200 mg of ozone per hour seen in the [March 2011] Amazon Ad? We don't know because the 200 mg number looks incomplete. If that 200 mg of ozone is being produced over an hour in a 1000 cubic foot room, that would be a very low concentration of ozone. 1000 cubic feet = 23,317 liters. 200 mg of something distributed into 23,317 liters amounts to about 0.0085 mg per liter or about 0.0085 ppm. In other words, almost nothing.

How much is 8 mg/hour ozone output seen at the OZN-jr product web page [March 2011]? Following the calculation above, output is 0.0003 ppm - almost less than nothing.

In our OPINION, at those ozone output levels your machine would not be hurting anyone, but it also would not be doing much that you'll notice either. Our detailed text below states that " ... the odor of ozone can be detected and identified by most people at a concentration of from 0.02 to 0.05 ppm (parts ozone per million parts air + ozone)."

Watch out: there is a very wide range of ozone output from different types of ozone generating equipment, and some equipment can be used at output settings or in enclosed environments to produce levels of ozone gas dangerous to occupants and damaging to building contents.

What is the Legal Definition of "Up To" in Advertising Claims

With an advertising attorney we recently discussed the legal requirements for advertisers who make "up to" claims. She informs us that in the U.S. law on "up to" claims requires that the product meet the "up to" claim at least ten percent of the time.

Translating this into plain language, in a given installation the OZN-jr can meet its advertising claims if in ten percent of cases it deodorizes 1000 cubic feet (that's a room that is about 8 feet by 15.6 feet or 125 square feet if the ceiling height is also 8 feet). And 90 percent of the time it can perform less well, or even not at all.

The ability to deodorize a space using just about any deodorizing method (other than complete removal of the odor source) depends on other variables that are certainly not under the product manufacturer's control, such as the level of odor or smell in the first place, the persistence and nature of the odor source, building air movement properties, space size, equipment location, and lots more.

Toxicity of Ozone Gas

The following information about Ozone is quoted from "Health Hazards of Some Gases" with minor edits and additions. SeeReferences or Citations [8]

"Ozone is a kind (called an "allotrope") of oxygen . It is formed in the ionosphere by the action of ultraviolet radiation from sunlight on oxygen. Lightning strokes are another natural source of ozone and the characteristic odor of that material can often be noted during and after a thunderstorm.

When pollutants are emitted into the air either by man or nature, almost all are eventually removed by one or more of several processes including reaction under the influence of ultraviolet radiation. One series of such reactions results in the formation of ozone as a "secondary" (formed by reaction in the air) air pollutant, often in rather high concentrations (several tenths of a part per million).

"As ozone can be formed by nature's sparks (lightning), it can also be formed by man's. Whenever an electrical spark or corona occurs in air, some ozone is formed. This accounts for the characteristic odor noted near an operating electric motor such as an electric shaver.

"Because ozone is found in so many places, its toxicity (ability to injure a living organism by other than mechanical means) has been investigated extensively since the early 1900s. Experimentation has shown that the odor of ozone can be detected and identified by most people at a concentration of from 0.02 to 0.05 ppm (parts ozone per million parts air + ozone).

As the concentration increases to a few tenths of a part per million, the first effect noted is likely to be a feeling of dryness in the back of the throat. If a concentration on the order of 0.2 or 0.3 ppm is inhaled more or less continuously for several hours to a few days some lung irritation may result.

"Higher concentrations can produce several kinds of toxic effects if exposures are sufficiently prolonged. Eye irritation (despite newspaper and TV accounts seemingly indicating otherwise) occurs only at concentrations high enough to result in other, more severe, toxic effects.

Reactivity of Ozone Explains Both its "Odor Killing" feature and its Role in Creating New Oxidized Material Odors

"Ozone is a very reactive substance. It will readily react with just about any material capable of being oxidized, and with many that are not. The material with which it reacts may be a gas or vapor, a particle floating in the air (a mold spore, for example), or a solid (or liquid) surface.

For this reason, when ozone is present in most enclosed spaces its concentration declines quite rapidly with time. Of course, if ozone is being generated more rapidly than it is destroyed by reaction, its concentration can build up.

This is the main reason why devices that produce relatively large amounts of ozone are safe only in relatively large enclosures and why the ozone generation rate should be reduced in small enclosures.

Separately at OXIDATION OF BUILDING CONTENTS, CARPETS, COATINGS - MIS-USE / OVERDOSE of OZONE we explain what happens when someone "over-doses" a building or a vehicle with ozone.

"Ozone is well known for its ability to eliminate certain odors. How this is accomplished is controversial. At concentrations just above the odor threshold, some odors do seem to vanish.

The main reason for this may be ozone's ability to desensitize the olfactory apparatus so that the odors can no longer be perceived. Some evidence indicates that this may be the case at least occasionally.

Other evidence indicates that ozone may react with the odor-causing substances, eliminating them from the air (this is probably the only mechanism that operates when concentrations are below the odor threshold).

"Finally, some people have insisted that even if ozone does not paralyze the olfactory sense, its odor is such that it "masks" other odors. Perhaps all three mechanisms operate, each in its own area of effectiveness.

At What Level Can People Smell Ozone?

"Because ozone is found in so many places, its toxicity (ability to injure a living organism by other than mechanical means) has been investigated extensively since the early 1900s.

Experimentation has shown that the odor of ozone can be detected and identified by most people at a concentration of from 0.02 to 0.05 ppm (parts ozone per million parts air + ozone).

At What Exposure Level Can Ozone Affect People?

As the concentration increases to a few tenths of a part per million, the first effect noted is likely to be a feeling of dryness in the back of the throat. If a concentration on the order of 0.2 or 0.3 ppm is inhaled more or less continuously for several hours to a few days some lung irritation may result.

"Higher concentrations can produce several kinds of toxic effects if exposures are sufficiently prolonged. Eye irritation (despite newspaper and TV accounts seemingly indicating otherwise) occurs only at concentrations high enough to result in other, more severe, toxic effects.

Health Effects of Ozone Exposure

"As with all other materials, ozone has a dose-effect relationship with a threshold. That is, once the threshold dose has been exceeded, toxic effects are proportional to dose

For inhaled gases, dose is proportional to both time and concentration. If the duration of exposures cannot be controlled (as is usually the case), then the concentration must be kept low enough so that no injury will occur even from prolonged and repeated exposures.

For ozone, that "threshold" concentration is 0.10 ppm.

So long as concentrations are kept at or below that level, injury is not expected even in the most sensitive workers so long as their exposure durations coincide reasonably well with or are less than the 8 hr/day, 40 hr/wk regimen.

This "threshold" level is accepted by the American Conference of Governmental Industrial Hygienists (and is called the Threshold Limit Value by that organization) and by the Occupational Safety and Health Administration, OSHA.

The TLV or OSHA's Permissible Exposure Level (PEL) is not a fine line between safe and non-safe

Instead, it represents the best judgment of a group of experts of the highest concentration that can be inhaled repeatedly by a population of workers with no resulting injury. Higher concentrations may or may not have any particular effect on a specific individual.

"Ozone is a highly toxic gas but even highly toxic substances can be encountered safely. The main concern with this material is that concentrations to which people are exposed do not average more than 0.1 ppm over an 8-hr day, and do not exceed that value by more than a factor of 2 or 3 during the exposure."

See more details about the exposure limits for ozone at OZONE HAZARDS & OZONE TOXICITY LEVELS

Watch out: the temporary and long term effects of exposure to high levels of ozone can be serious. While most of the effects described by researchers relate to lung or pulmonary function, there may be other effects.

Watch out: also, that much ozone exposure research has focused on ozone levels in outdoor air in cities with poor outdoor air quality, such as Mexico City (Castillejos 1995) and other cities (Hoek 1993).

In contrast, our article series describes potential hazards from high doses of ozone inside buildings, or in vehicles, such as misuse of an ozone generator to try to "kill" mold odors. Those indoor ozone levels, during the time that ozone is being generated, may be much higher than the outdoor ozone levels in most of public health studies.

The following is excerpted from information provided by the U.S. Environmental Protection Agency (US EPA) and pertains principally to outdoor ozone exposure

Ozone can:

• Make it more difficult to breathe deeply and vigorously.
• Cause shortness of breath, and pain when taking a deep breath.
• Cause coughing and sore or scratchy throat.
• Inflame and damage the airways.
• Aggravate lung diseases such as asthma, emphysema, and chronic bronchitis.
• Increase the frequency of asthma attacks.
• Make the lungs more susceptible to infection.
• Continue to damage the lungs even when the symptoms have disappeared.
• Cause chronic obstructive pulmonary disease (COPD).

These effects have been found even in healthy people, but can be more serious in people with lung diseases such as asthma. They may lead to increased school absences, medication use, visits to doctors and emergency rooms, and hospital admissions.

Long-term exposure to ozone is linked to aggravation of asthma, and is likely to be one of many causes of asthma development. Long-term exposures to higher concentrations of ozone may also be linked to permanent lung damage, such as abnormal lung development in children.

Recent studies consistently report associations between short-term ozone exposures and total non-accidental mortality, which includes deaths from respiratory causes. Studies suggest that long-term exposure to ozone also may increase the risk of death from respiratory causes, but the evidence is not as strong as the evidence for short-term exposure. 

- Source: U.S. EPA, "HEALTH EFFECTS OF OZONE POLLUTION", [PDF] retrieved 2017/08/19, original source: https://www.epa.gov/ozone-pollution/health-effects-ozone-pollution

Reader Question: What kind of lasting damage could acute ozone exposure cause in humans?

2017/08/19 Peeps said:

We recently had an ozone gas incident at work where people were experiencing muscle cramps, severe pain all over the body, headaches, muscle weakness etc.

We learned that the ozone laundry system was vented to a mop closet indoors that had an open pipe, so all of the gas was entering a fairly enclosed area.

This went on for months before someone recognized the leak and cemented up the pipe. What kind of lasting damage could this cause in humans?

Reply: Possible respiratory damage

Thank you for asking, Peeps.

Although ozone has impressive and effective uses as a disinfectant and in some medical procedures involved in healing, breathing high levels of ozone is harmful, as we discuss here and at OZONE EXPOSURE STANDARDS.

In OZONE REFERENCES & OZONE GENERATOR INSTRUCTIONS or

directly within that article at OZONE TOXICITY RESEARCH you'll see that most research on the injury to humans has focused on respiratory issues, lung or pulmonary function, and (I believe probably a closely-related but still indirect) effects on actual mortality, usually among people at extra risk such as asthmatics, the elderly, and children.

Separately we provide this TABLE of OZONE GAS EXPOSURE EFFECTS, Risk Factors, & Standards.

and we also provide advice at 3 STEPS to ASSESS POSSIBLE HARM from OZONE GAS O₃ EXPOSURE

You cite a variety of complaints, cramps, muscle pain, headaches, weakness among people who might have had a high ozone exposure, though we should not rule out, from your brief description, possible exposure to other gases, chemicals, or particles coming from the laundry vent system such as laundry soap scents, lint and dust particles, and mold that might be stimulated by high moisture in some building areas.

As someone who is not a medical research expert can but speculate that there is an interesting possible connection between muscle cramps and the effect of ozone on asthmatics, since an asthma attack involves cramping or a muscle spasm in the smooth muscle in the human airway, causing in turn bronchoconstriction. But that's just speculation.

A Google Scholar search for "muscle cramps caused by ozone" produced little outside of asthma research beyond (Baabor 2011 and Preisser 2012) both of whom are cited at OZONE TOXICITY RESEARCH.

Preisser was not specifically discussing ozone as a fumigant but report: Headache, concentration and memory disorders, dizziness and nausea, skin irritation, respiratory distress, and muscle cramps — isolated or in various combinations — may be the result of acute or chronic intoxication by fumigants. (Preisser 2012).

Searching for "muscle pain caused by ozone" finds article on the treatment of muscle pain or back pain by ozone-oxygen therapy rather than discussing ozone as a cause of muscle pain.

Searching for "headache caused by ozone exposure" was more productive (Jörres 1996) " our data suggest that short-term exposure to ozone can increase bronchial allergen responsiveness in subjects with mild allergic asthma or rhinitis." for which dizziness and nausea were among the complaints. (Dorado-Martínez 2001) reported memory impairment in rats and in the article text cites "The observation that ozone causes effects in ... comprising nose and throat irritation, cough, chest tightness, shortness of breath, headache, nausea, thirst ..."

Searching for "weakness caused by ozone exposure" was not productive.

...

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

Or see these

Recommended Articles

• 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

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Citations & References

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