Using Ozone to Kill and Denature Mould

The Effectiveness of Ozone Generators on Mould, Mycotoxins, Fragrance and Smoke 

Ozone kills and denatures mould on surfaces, eliminates many VOCS and odours such as perfume. It can also remediate smoke smell in certain materials. 

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.

For those who prefer a video format, I have explained the process of a shock treatment and the risks in this video.

For individual help with using ozone safely for your application, you can schedule a consultation with me here.

Does Ozone Denature Mold and Mycotoxins?

Some say that ozone kills mould spores but does not denature the toxins (EHC). These two studies show it can denature the toxins. Based on these two studies (that use very very high amounts of ozone), and the experience of me and those extremely sensitive to mycotoxins left over after remediation, 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 doses 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 mould and see what works for you, and be prepared for byproducts (discussed more below).

Which Ozone Generator to Use

I started with the Jenesco Ozone Generator with an output of 100-2100 mg. 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.

This one comes in around $400

I have have little Airtherial 5000 mg one (pictured left) this is the lowest cost one I have seen. If you are doing a shock treatment for mould 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 what I would use for going after fragrance and smoke as well as cleaning product residue. You don't want a high dose for that application.

Results with Offgassing, Mould, Fragrance, Smoke


- Chemical smell in Camplite trailer reduced after a few treatments

- Glue smell reduced in brand new metal cargo trailer (this seems to work really well o 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


- Mould remediated in all metal trailer after 48 hours high dose

- I also had a mould problem in another house I was living in. After the mould 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. This for me definitely denatures mycotoxins. I have also done 48 shock treatments in metal trailers that were very effective. (I let in oxygen during that time).

- 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. It seems as though 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.

-Some people found it useful to shock a room or tent, and to "flash" belongings before any mould toxins could take hold.

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 when 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 is very useful if fragrance and smoke smell are your big concerns. Go low and slow on fragrance, cleaning product residue and smoke until you start to see a difference. 

To remove odours the time needed for treatment is much less than the shock treatment for mould. This will reduce a lot of the risks. Car detailers run ozone for 15 min to 2 hours, typically, or until they can removed the smoke or other problematic odour. 

You have to be sure you are using it safely and understand the limitations -

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). It clings to your clothes even if you hold your breath and walk through - this is not safe.

- Ozone needs to be 5-10 x above safe levels for humans to impact bacteria and mould (Pinto).

- The place should be aired out 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 air flow. 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 tonnes of open windows for the air out.

- One reason government health sites do not recommend the machines is that the shock treatment used to get rid of mould 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. So there is a huge risk if someone does not know how to use it safely. It is possible they are also wary 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 mould or chemicals (EPA). My experience suggests that it does denature mould that is near the surface of pourous materials. I don't think it goes very deep.

- It will not help with chlorinated hydrocarbons (vinyl, plastics etc) (EHC)

- 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)
  • 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.

High doses of ozone used to really clear out mould toxins will also degrade or harm certain materials such as:

  • Plants
  • Rubber (especially vulnerable is natural latex)
  • Coating of electrical wires
  • Fabric
  • Some artwork
  • Unfinished metal will rust

My experience is you really need to do many many treatments before you start breaking down most rubbers.  I have done many high dose (shock treatment) ozone treatments and not broken down coatings on electrical wires. 

Folks to ozonate electronics with success (just don't do it too many times and if the rubber parts are already close to breaking down you could have a huge problem). 

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. 

Hold your breath while turning it on and while turning it off. Air out the place with fresh air for 24 hours. This is based on my experiences. 

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. 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 use 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 mould is usually 1000 milligrams per hour (mgph) 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. 

The machines I like are the Jenesco Ozone Generator with an output of 100-2100 mg. And the little 5000 mg ones on Amazon that are low cost with a "hold" setting.


Michael Pinto:

Corinne Segura is a Building Biologist with 5 years of experience helping others create healthy homes.

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Same Day Inspection said...

What is a good home mixture to remove blackmold? I believe a mixture of bleach and soap and water works, but I'm not sure.
insulation inspection

Dat Hoang Tien said...

Nice post!

8905 said...

In what negative ways exactly will an ozone shock treatment affect older carpeting?

8905 said...

In what negative ways exactly will an ozone shock treatment affect older carpeting?

Corinne said...

It reacts with all cloth materials to form a biproduct. It has a very weird smell and hard to describe.

Corinne said...

It creates a bad smell.

Tatiana Irvine said...

How do you protect the ozone machine itself from becoming contaminated (with mold/mycotoxins)...and then cross-contaminating a different space?

Corinne said...

The ozone at high doses breaks down the mycotoxins so I'm not sure how the machine would become contaminated.

Wild Swan said...

We physically remove mold in the properties we purchase. If a wall shows mold on the interior of the drywall, we take out the drywall to examine the studs. The studs almost always show mold, in which case we remove the wall down to the wall plate to reach the concrete foundation wall. Bleach does not reach the roots of the mold, the EPA has essentially admitted it doesn't work for cleanup, after many years of advocating it.

kim said...

If there is a smell in fabrics after using ozone machine for 24 hours, is there any way to get rid of it? And how might go go about getting rid of any residual smell in the house after 24 hours?

Thank you!

Hasselhoff said...

I think I overdid it in a bathroom. I had kept the door shut while running an ozone machine for 10hrs. Got rid of the a odor issue we were having, but left a very strong chemical-like odor afterwards. It's been 4+ months, and after constant airing out it still smells acrid. I can't stand going in there and keep the door shut.

Wondering if your situation has improved with time?


Corinne said...

It did improve but I never went back to live in the house that I ruined with ozone. So I'm not sure how long it would take to go away. A lot depends on what it reacted to and if you are super sensitised to it now.

Hasselhoff said...

Thanks for getting back so quickly. Sorry to hear you are not able to go back.

Thinking I've just become hyper sensitized. There's some days I feel like that 'smell' is everywhere. Very strange. Other people notice a faint 'off' smell, but have no problem with it. It might have reacted with the paint or tile adhesive; like a sweat plastic odor. Thinking to just refinish the entire bathroom now.

Sounds like you generally had success with ozone treatments. Do you continue using it?

Augsnod said...

My ozone generator has been a life-saver for me. I've lost nearly everything due to MCS and finding a safe home was vital, along with all the products that I have to live with. I've used my generator to make so many things safe, including my home itself, plastic products from China, fabrics with laundry chemicals, and even new clothing that was unwearable. The key to successful treatments – for me – is short duration usage followed by adequate ventillation. I usually do 15 minute treatments followed by hours of settling time. I'll get faint whiffs of ozone, but it goes away pretty quickly. I've had some very difficult situations that I've done repeated treatments of about an hour, but that's the longest that I've used it.

For those interested: I bought a bare-bones generator that is very inexpensive. The company has useful information for using these machines, and one of the most useful pages is the one on mold: instead of advocating that people purchase their product for mold, they advise against it in favor of professional remediation.

Corinne said...

I have one of their machines as well. It seems they are not selling them anymore and I was not even able to get a plate order it (though of course you can buy those plates anywhere). They are absolutely the most bang for your buck but I cannot promote a machine with so few safety controls on it. I tried to ask them some questions about the construction bc there is a possibility in certain conditions, with a broken plate, depending on how it is made that can delivery a deadly shock. It has no cover on it and does not look like it has proper safety measures.

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