The Effectiveness of Ozone Generators on Mold, Mycotoxins, Fragrance, and Smoke
Ozone kills and denatures mold on surfaces, and breaks down many VOCs and odors such as perfume. It can also remediate smoke smell in certain materials.
Ozone has also caused a lot of damage, not just to the breakdown of certain materials in a home, but it seems to exasperate some toxins, causing many people to not be able to return to their house for a long time, or ever.
This post contains affiliate links to relevant products that I use and recommend. Upon purchase, I earn a small commission at no extra cost to you.
Please take full responsibility for your safety when using ozone. Make sure you read and understand all the precautions in this post. Full disclaimer is here.
Expert Review: This post has been reviewed by Tim David, HVAC professional with 30+ years experience.
Does Ozone Denature Mold and Mycotoxins?
Some say that ozone kills mold spores but does not denature the toxins (EHC).
Based on these studies, and the experience of me and those extremely sensitive to mycotoxins, I do think it is accurate to say ozone actually kills and denatures mold.
It can still be a good idea to HEPA vacuum after ozonating to clean up dead spores.
A shock treatment is either a very high dose for shorter amounts of time or very long treatments (from 24 hours to 48 hours). You really have to experiment if you want to denature mold and see what works for you, and be prepared for byproducts (discussed more below).
The main drawback is the dose of ozone needed to denature mold also breaks down and oxidizes many other materials.
I personally would never try this again, even though I saved one house I lost another. It seems that it aggravates some toxins to the point where some people cannot return.
You should never be in the room with any device that is producing ozone for any amount of time. Read ALL the safety precautions in this post.
Which Ozone Generator to Use
I started with the Jenesco Ozone Generator with a high output. This is a high-quality unit with a timer and dosage control. I liked this unit because it’s well made and, the timer settings and dosage control setting were useful.
I have the little Airtherial 5000 mg one (pictured left) this is the lowest cost one I have seen.
If you are doing a shock treatment for mold you need one with a hold setting like this one.
If you are using it at low amounts for fragrance you will only need the basic timer.
You cannot control the dosage with these little inexpensive ones, but you can find them for under $100 on Amazon.
For only a little more than a hundred, you can buy this Ivation model which can dial down the dose from 6000 mg to 500 mg.
This is a better idea for going after fragrance and smoke as well as cleaning product residue.
You don’t want a high dose for these applications, start as low as possible. You should still be out of the space at low doses.
Results with Offgassing, Mold, Fragrance, Smoke
Using Ozone on Offgassing
- Chemical smell in Camplite (metal) trailer reduced after a few treatments.
- Glue smell reduced in brand new metal cargo trailer (this seems to work really well on the new glue smell in basic trailers).
- I would not use this is a new house or conventional trailer (that is full of plastics and upholstery) to reduce offgassing, it’s too risky and does not work that well.
Using Ozone to Break Down Mold
- Mold remediated in an all-metal trailer after 48 hours of a high dose.
- I also had a mold problem in another house I was living in. After the mold was remediated I was still very sick – throat swelling, extreme POTs and terrible insomnia. I then ozonated each room for 24 hours with the machine and was able to come back without any symptoms. I removed all the fabric and cushions from the area before ozonating and there were no adverse chemical reactions with the wood or anything else in the house.
- I’ve used it 4 times now in post remediations with a 24-hour shock treatment. I feel certain this denatures mycotoxins. I have also done 48 hr shock treatments in metal trailers that were very effective. (I let in oxygen during that time).
- Some people found it useful to shock a room or tent and to “flash” belongings before any mold toxins could take hold.
- However one of these times the 24-hour treatment created horrible byproducts in a wooden house. Even after excessive airing out, I got extremely sick. I overdid the ozone or did not have enough oxygen coming in. Big risk here. It was a long time before I could go in that house again.
- The last time I used ozone something went terribly wrong, it felt increidbly toxic after and I had severe reactions, and I was never able to return to that rental house. My belongings were ruined as well. I would never risk high dose ozone again.
Using Ozone to Eliminate Fragrance, Smoke and Funky Smells
- Smell removed from funky smelling fabric (towel that had a smell that washing would not remove).
- BUT: gave some fabrics like wool and cotton a strange smell after doing an intense 24 treatment.
- Ozone can help a lot with fragrance in a car or house as well as smoke smell. Car dealerships use ozone but not super high amounts of for long amounts of time. This works best if the fragrance wasn’t used over time, it’s not deeply imbedded. If deeply imbedded this is unlikely to work.
- This is very useful if the fragrance and especillay smoke smell are your big concerns. It’s better to go low and slow on fragrance, cleaning product residue, and smoke until you start to see a difference.
- To remove odors the time needed for treatment is much less than the shock treatment for mold. This will reduce a lot of the risks. Car detailers run ozone for 15 min to 2 hours, typically, or until they can remove the smoke or other problematic odor.
You have to be sure you are using it safely and understand the limitations.
Do not be in the same room as ozone gas, ever, for any amount of time and make sure you understand the risks of oxidization of materials.
How to Use Ozone Safely
- Ozone is a very toxic gas.
- People and pets should not be in the building when an ozone machine is on. Do not even take one whiff of it. Make sure you have a plan to turn it on and off while holding your breath. Ideally, turn it off without entering the room (through the electrical panel or extension cord). It clings to your clothes even if you hold your breath and walk through – this is not safe.
- Ozone can be harmful from 100 ft away or more if it’s a high dose, it can harm others in the area including neighbors. Clear 200 ft in every direction if before using a high dose.
- Ozone needs to be 5-10 x above safe levels for humans to impact bacteria and mold (Pinto). You cannot treat mold and be near it.
- The place should be aired out for 25 hours minimum after using ozone to make sure that the gas is not inhaled. Ozone is unstable and will dissipate, but it does not dissipate as fast in a closed space with no airflow. If other VOCs form (see below) then it is necessary to air out the place for a while.
- The half-life of ozone is 40 min-25 hours. If byproducts have been created then give it a few days at least. Make sure there are tons of open windows for the air out.
- One reason government health sites do not recommend the machines is the shock treatment used to kill mold toxins is a very harmful level if inhaled (deadly if you stay in there). Even the low levels recommended as safe by some manufacturers is probably harmful to anyone sensitive to toxins (certainly it is harmful to me). So there is a huge risk if someone does not know how to use it safely. It’s also difficult to recommend in most houses because of the negative reactions outlined below. In many conventional houses, it might not be possible to avoid all those secondary reactions with materials.
Limitations of Ozone
- Ozone cannot remove carbon monoxide or formaldehyde (EPA).
- It cannot get into porous materials to remove mold or chemicals (EPA). My experience suggests that it does denature mold that is near the surface of porous materials. I don’t think it goes very deep.
- It will not help with chlorinated hydrocarbons (vinyl, plastics etc) (EHC) nor phthalates (Arlene Blum).
- May not work on clothes and shoes (Pinto). My experience is that there is a bad reaction with any fabric in high amounts. But lots of folks have had success remediating clothing and shoes including leather shoes. Though not all types of leather will hold up the same and some rubbers in shoes will eventually break down.
Negative Reactions and Byproducts of Ozone – What Can go Wrong!
Ozone reacts negatively with some compounds creating more VOCs. Some of the substances it reacts to are:
- New carpets (EPA)
- Active tobacco smoke (EPA)
- Terpenes (to form formaldehyde) (CDH)
- Styrene (EHC)
- Floor finish that contains pinine (Pinto)
- Ceiling tiles (from a client of mine)
- Old carpet (from a client of mine)
- Fabrics (from my experience and from clients)
- Wallpaper (from a client)
I have found there is a negative byproduct left with almost every porous material if you do this in high enough doses for long enough. Ozone oxidizes everything and this leaves an odor behind that can be harmful.
Cotton oxidation byproducts include ketone, aldehyde, carboxylic acid, ester, anhydride, and unsaturated hydrocarbon structures.
High doses of ozone used to really clear out mold toxins will also degrade or harm certain materials such as:
- Plants can die
- Natural latex/natural rubber is extremely vulnerable to break down.
- Styrene-butadiene rubber (SBR) is vulnerable (tires, many shoes, some gaskets, liquid waterproofing in basements, parts of electronics like in speakers, in lithium-ion batteries, and gasketed-plate heat exchangers).
- Nitrile rubber will break down easily (some rubbers are fairly resistant).
- Caulking can break down
- Some Plastics, see these two lists of how vulnerable different types of plastic are.
- All types of nylon are extremely vulnerable to break down.
- Some artwork
- Steel will rust
This is not a comprehensive list, there may be more household materials that contain these components. And many other materials have not been put to the test.
I have done many high dose (shock treatment) ozone treatments and not broken down any coatings on electrical wires. Most wires are coated with PVC which is fairly resistant to breakdown from ozone. But it will eventually be damaged by ozone.
Though if you have electrical lines coated in a different type of plastic or rubber it could break down and become dangerous. I haven’t seen this happen, but it’s possible. Please double-check the types of wiring you have. There may also be SBR in electronics, which is much more vulnerable.
Folks do ozonate electronics with success. It could be risky if you don’t know what plastics are in it, there is a risk of breaking down electrical components leading to electrical shock.
I have seen Taylor guitars remediated with success.
How to do an Ozone Shock Treatment
For a shock treatment, remove everything fabric or wrap them in plastic, this includes mattresses.
Remove plants, pets, and artwork that is not behind glass. Tape up electrical outlets. Remove all electronics. Make sure you have everything you need before turning the machine on.
(Really plastic and tape does not fully block ozone but I still think that’s worth doing).
Hold your breath while turning it on and while turning it off (or use an extension cord or cut it from the breakers). Air out the place with fresh air for 25 hours. This is based on my experience.
Make sure you research if this is safe for you and worth the risk. Understand why the EPA does not recommend it. It is too easy to do something wrong where you could breathe some in. Treat it like the deadly gas that it is.
If you are not sure if it will react with your carpet, walls, ceiling then it is a last resort treatment.
I would not consider doing a shock treatment anymore.
You can also test a low dose first to see if any weird smells form.
Make sure it is dosed correctly for the space and if running it for 24 hours it needs an oxygen source.
Overdoing it can make your place intolerable. I recently had a bad experience where I overdid it with the ozone, it took a month to be able to go back in.
How to Dose Ozone
I generally used 3500 mg/hr in a single medium-sized or large room for a shock treatment. A shock treatment which is what kills and usually denatures the mold is usually 1000 milligrams per hour (mg/h) per 100 sq feet (at 70 degrees with relative humidity at or below 20%).
The level you are aiming for is 6 to 10 parts per million. Many people shock for 1-3 hours but those of us super sensitive tend to keep going until the substance is denatured. I have gone as high as 5000 and 7000 mg/hr in a very small trailer for 24 – 48 hours.
- EPA: www.epa.gov/iaq/pubs/ozonegen.html
- CDA: www.ct.gov/dph/lib/dph/environmental_health/eoha/pdf/ozone_generator_fact_sheet.pd
- EHC: www.environmentalhealth.ca/summer96ozone.html
- Michael Pinto: www.moldsensitized.com/ozone-generators-and-interior-mold-remediation-a-recipe-for-disaster/
- Arlene Blum, Chemist: www.sixclasses.org
- CraftTech Industries: www.craftechind.com/top-8-ozone-safe-plastics/
- Ozone solutions: www.ozonesolutions.com/knowledge-center/ozone-compatible-materials.html
- Apple Rubber: www.applerubber.com/hot-topics-for-engineers/understanding-the-link-between-ozone-and-rubber-deterioration/
- Oxidation of cotton: https://pubs.acs.org/doi/10.1021/ba-1993-0236.ch029
Corinne Segura is a Building Biologist with 8 years of experience helping others create healthy homes.
Expert reviewed by Tim David, HVAC professional with 30+ years experience, CEO of Airlucent.
Did you find this post helpful? If so you can buy me a coffee to support the research behind this blog. Thank you!