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Ozone: The Good, the Bad, and the Ways to Keep You & the Animals Safe

Ozone: The Good, the Bad, and the Ways to Keep You & the Animals Safe

By Annette Uda

“Good up high, bad nearby”

That’s how the Environmental Protection Agency (EPA) succinctly describes ozone, a gas composed of three oxygen atoms that occurs both in Earth’s upper atmosphere and at ground level.

Ozone can be “good” or “bad” for the environment, your health and the health of the animals in your care, depending on its location in the atmosphere.

Good Vs Bad

“Good” ozone “up high” is the naturally produced layer that sits six miles above Earth and protects it from ultraviolet rays that cause skin cancer, cataracts, crop damage and disruption of marine ecosystems, among other problems. Decades ago, scientists sounded the alarm that the ozone layer was thinning and a hole was forming in it. The ozone–depleting culprits were identified as man–made chemicals (chlorofluorocarbons), and the world decided to do something about them.

As described by the U.S. Department of State: “The Montreal Protocol, finalized in 1987, is a global agreement to protect the stratospheric ozone layer by phasing out the production and consumption of ozone-depleting substances (ODS).”

In November 2018, the United Nations issued a report that Earth’s protective ozone layer could fully heal within 50 years. There is still a long way to go, but scientists were very encouraged by the report. By working together, the world may have saved the ozone layer. Good news for good ozone.

“Bad” ozone “nearby” is found at ground–level.

As described by the EPA, “This ozone is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. Emissions from industrial facilities and electric utilities, motor vehicle exhaust, gasoline vapors and chemical solvents are some of the major sources of NOx and VOC. At ground level, ozone is a harmful pollutant.”

Ironically, some air purifiers actually make the air you breathe more dangerous by emitting ozone. But what about ozone used for water treatment? Isn’t that “nearby”? Yes, but it’s not bad.

Confused yet? Don’t be. Just stay focused on what will keep you and the animals in your care safe and healthy. The following is what you need to know.

“Ozone Alert” Safety

Depending on where you live, you may be familiar with “Ozone Alert” or “Ozone Action” days when local authorities alert the public that the ozone pollution is at a level that may cause health problems. These alerts typically occur during the summer months when strong sunlight, hot weather and humidity can cause dangerous concentrations of ozone.

As described by the EPA, breathing ozone can trigger a variety of health problems including chest pain, coughing, throat irritation and congestion. It can reduce lung function, inflame the linings of the lungs and worsen bronchitis, emphysema and asthma. Healthy people are not immune to the effects of exposure to ozone pollution, and neither are pets. On days when air quality is poor, keep your furry clients inside as much as possible, avoiding strenuous outdoor activities. Also keep windows closed during air quality alerts so that the air inside is safe as well.

While all pets should be kept safely inside, as noted by Dr. Wendy McClelland, DVM, in her article ‘Very High Risk’ Air Quality Affects Pets, Too: “Pets with short noses and flat faces such as Boston terriers, Pugs, Bulldogs, and Shih-Tzu’s—and cats such as Himalayan, Persian, and Scottish Fold—are particularly at risk for respiratory issues during high–risk air quality alerts.”

In his article, Pet Care Facility Weather Emergency Preparedness: You’re Ready, Right?, safety expert Ben Day recommends designating a team member responsible for monitoring weather updates to communicate to the rest of the staff. This weather emergency protocol should extend to Ozone Alert days. Air quality forecasts are often provided with local weather forecasts. The EPA suggests you can also check ozone levels and other daily air quality information by visiting, and in many areas you can receive air quality notifications through

HVAC Maintenance

Be sure to have a year–round schedule of maintenance in place for your HVAC system. For most buildings, HVAC filters should be changed at least every three months, but animal care (just think of all that flying fur) can require greater frequency. Depending on how dirty or plugged the filters get, they should be changed as often as every two weeks, but certainly at least once a month. Be sure to check your HVAC manual to see what kind of filter you need to buy.

Your HVAC system’s evaporator coils are also an integral part to maintaining safe, clean air as the indoor air blows over them. If your system does not include commercial–grade UV to keep the coils clean, they can become dirty as dust and dander settle on them along with “biofilm”, a build–up of microorganisms that creates an impenetrable layer over the coils. Not only do dirty coils prevent the HVAC system from working efficiently, demanding increased electricity to function and decreasing air flow, but they can also create breeding grounds for bacteria. If you don’t have commercial–grade UV as part of your system, cleaning the coils should be part of your regular routine.

Be sure to consult your HVAC manual for more information specific to your system, but be aware of this important caveat: if you wait too long to clean your coils, not only will the biofilm be more difficult to remove, but aggressive cleaning to try to do so can result in damage to coils.

Air Purifier Safety

Just by virtue of their name, you would think air “purifiers” are safe, but if they produce ozone – intentionally or unintentionally—simply put, they are not. Good Housekeeping makes no bones about how seriously they take ozone when it comes to air purifiers. From their article, Health Hazard: Air Purifiers That Give Off Ozone:

“If you don’t live in California, which has banned the sale of ozone–generating purifiers (unless the amount of ozone they emit is very, very low), you’ll still see these purifiers for sale in stores and on–line. Don’t buy them. We feel so strongly that these products are hazardous to your health that we will not allow them to apply for use of the Good Housekeeping Seal or advertise in Good Housekeeping. If you already own an air purifier, make sure it doesn’t produce ozone and if it does, stop using it and cut the cord before you discard it so no one else can use it either.”

On its website, the government of New South Wales in Australia has information on ozone generators as part of its Environmental Health content:

“What does an ozone generator do?

An ozone generator is a device designed to produce the gas ozone. Ozone is used effectively in water purification, but ozone in air must reach high levels to remove air pollutants.

Health experts warn that it is important to control conditions to ensure that no person or pet becomes exposed to high levels of ozone. Ozone also masks the odor of some pollutants by impairing a person’s sense of smell.

Further, ozone is not effective for killing bacteria or mold in materials such as air conditioning duct lining and ceiling tiles.”

If you go on online right now and enter a search for “ozone generator” you’ll receive an abundance of purchase options. If ozone generators are as bad as Good Housekeeping strongly believes, and as apparently ineffective as the New South Wales government indicates, why are they still so abundantly available—except in California?

If you read the five–star online reviews, people appear to love them for their purported odor–killing ability (or is your sense of smell simply impaired as suggested above?), but encourage you to follow the manufacturers’ warnings and directions for use (you and pets should not be in the room when in use, for example).

But, as noted in the EPA’s 2005 publication, Ozone Generators That Are Sold as Air Purifiers: An Assessment of Effectiveness and Health Consequences, “The results of some controlled studies show that concentrations of ozone considerably higher than (published) standards are possible even when a user follows the manufacturer’s operating instructions.”

Further, and of particular importance to pet care providers, air purifiers that generate ozone deemed within “safe” limits established by government regulations, do not necessarily mean safe for animals.

How do you know if your air purifier produces ozone, even unintentionally? Do your research and ask questions. And be aware that air purifier safety extends to UV systems. If your HVAC system is equipped with UV or you are using upper air or mobile service systems, make sure those UV systems are not producing ozone.

The sad reality is in taking steps to improve air quality and prevent the spread of infectious disease, you may be putting your staff and the animals in your care at risk with a UV system that produces ozone. Again, do your research and ask questions. What kind of UV technology does your manufacturer use? Can they assure you no ozone is produced?

Water Treatment Safety

Finally, what about ozone used to treat water? Why is ozone used to purify water safe when it’s ozone that is inarguably “nearby”? The simple answer: science. As noted above, ozone is a gas composed of three oxygen atoms and, when utilized for water purification purposes, it immediately degrades back to oxygen. Water ozonation is a different animal from ozone generators used as air purifiers. Ozone water purification systems are specifically made for treating water but, as always, do your research and ask questions.

Annette Uda is the founder of PetAirapy, the animal care industry’s leading manufacturer of UV surface and air sanitation equipment. Annette has a passion for animal health and educating animal care providers on reliable, non-toxic ways to create clean, healthy environments for your animal clients and your staff that are protected from airborne pathogens, infectious disease, and noxious VOCs. PetAirapy also recently launched FreshAirapy, its natural, non-toxic line of products for targeted, immediate odor control specifically for the animal care industry. To learn more about her company, visit