Ozone Generators and Safety

Ozone is an excellent water sanitizer because it kills 99.99% of bacteria, viruses, fungi, and other microbes that it comes into contact with. When set up and used correctly, ozone is safe for most people using it.

This post will cover the basics of setting up ozone to be safely used as a water sanitizer for your cold plunge.

DISCLAIMER: I am not a chemist or scientist. I care about people and I have been personally using ozone to sanitize my cold plunge water since 2018. I have not had any problems with my health or my environment or objects therein. My mission is to help people and I only use and recommend products that I believe to be safe.

NOTE: This article applies to both chest freezer and chiller-based cold plunges.

TLDR

1. If you have chemical sensitivities, COPD, or are recovering from toxic mold exposure, you *might* have a strong reaction to ozone.

2. How to run an ozone generator safely to sanitize the water in your chest freezer cold plunge:

• Only use ozone in a well-ventilated area
• Ensure that the gasket on the lid to your chest freezer makes a tight seal
• Ensure that the ozone tube is securely connected to the ozone generator
• Run the ozone generator once per day for the shortest amount of time possible (30 minutes up to 2 hours)
• Run the ozone generator on a timer and have it turn off at least 6-8 hours before people or animals are in the area.
• You can run it immediately after you leave the area.
• If you open the lid and smell ozone, step away for a few minutes to let it dissipate. Turn on a fan if needed.

Ozone and Hot Tubs

Ozone has been widely used in the hot tub industry since the 1990’s- countless millions of installations. We have hundreds of people around the world using ozone generators in their cold plunges since 2019, with only three reported issues. After a bit of detective work, it is most likely that there was another cause for one of these. Read below for details.

Chemical Sensitivities

In May of 2022 someone in our community seemed to have a reaction that could have been due to ozone being used in a chest freezer cold plunge set up inside an apartment. He had used a different ozone generator (very high concentration) previously in a different location to clean the air, and did not experience any issues with his breathing or the items in his home.

What changed? He reported using an ozone generator for water sanitation, which was being run for 30 minutes, once per day, into a tank with about 60 gallons of water in a chest freezer that was well sealed. He might have had a gap in his seal which allowed some ozone to escape. However, keep in mind that ozone is heavier than air and if any ozone did escape the chest freezer it would likely sink to the floor. He claimed that ozone damaged his health and caused a residual odor on many of the items in his home.

The first thing to note is that he later told me he had severe chemical sensitivities. That means that even one molecule of certain things (perfume, cigarette smoke, cleaners, etc.). can cause a severe immune reaction. I’m compassionate about that because while I do not consider myself to be chemically sensitive, in the years past, certain perfumes would cause me to have an immediate, intense pain in the top of my head for several minutes until after I could no longer detect the smell.

Ozone is very unstable, breaks down very quickly, does not linger, and does not leave a residual odor. I asked him to send the unit to me for inspection. When I opened the box, I immediately noticed a very strong odor of…. perfume!

I immediately recognized it because of the problems I used to have. It smelled nothing at all like ozone. My guess is that someone with a strong perfume came into his apartment and that is what caused the problem.

So, while it is highly unlikely that ozone caused the issue, I want to revisit a few reminders about safely using ozone. Most of this info has been mentioned many times before in my Facebook group.

The new piece of information to add is that if you have chemical sensitivities, COPD, or are recovering from toxic mold exposure, you *might* have a reaction to ozone. Why do I say “might”? Because after posting about this in my group two other people with severe chemical sensitivities say that they use ozone to clean the air in their homes, have had no problems, and are super grateful to have ozone cleaning their cold plunge water because they cannot use chlorine.

Two other families separately reported coughing and wheezing after starting to use ozone for their cold plunge. One setup was inside the basement of a home (NEVER RUN OZONE INSIDE!!), and the other was OUTSIDE on a covered patio. They were unable to determine direct causation but stopped using ozone to err on the side of safety.

The Basics

A typical small spa ozone generator designed for residential hot tubs, small pools, fountains, cisterns, and water tanks might output around 0.05 grams of ozone per hour. If they output more than that, it is likely to offgas too much ozone, which can not only be harmful to you, but can damage your equipment.

With hot tubs and pools, ozone runs through a length of tubing/plumbing and is impacted by the hot tub chemicals being used, which results in very little ozone (O3) coming out of the water. Why? Because it breaks down into O2. Some hot tubs have mixing chambers which further allows ozone to break down in the water before it is recirculated back into the main tub.

Fountains, cisterns, and water tanks are typically located outside and people are not typically sitting in the water.

Outdoor use of ozone for water sanitation should be perfectly fine because it is an open space and well-ventilated.

If your cold plunge is located outside (patio, porch, under a pergola, etc.) then there is almost zero risk of having any kind of problem when you follow the safety steps. Why almost? Very few things in life are 100%. And we have had exactly one person report that even when being used outdoors and run at night, ozone caused problems for him.

The Risks of Ozone

Before we go over the safety steps, let’s talk about the risk of breathing ozone.

Being around too high of a concentration of ozone- or even lower concentrations for long periods of time- can cause several problems:

• irritation in the eyes, nose and throat
• shortness of breath
• chest pain
• wheezing
• headaches
• coughing
• dry throat
• fluid in the lungs

Too much ozone exposure can damage lung tissue. Chronic exposure can lead to asthma.

Lungs can usually recover within a few days or weeks after exposure to high concentrations of ozone.

The type of exposure that typically causes health issues is found in cities with very poor air quality (ex. smog) and in industrial settings where workers are exposed to ozone every day for long periods over time.

How to Safely Use Ozone

So how do you keep it safe when sanitizing the water in your cold plunge?

First, ozone (O3) is highly unstable, and can only last about 30 minutes up to four hours before it converts back to oxygen (O2). How fast ozone breaks down into O2 depends on many variables, including the amount of microbes and sediment in your water, the water temperature, the volume of water and air space in your cold plunge, how well it is sealed, the ambient temperature, and ventilation in the area. Only run ozone outdoors.

With the relatively small amount of water in a typical cold plunge, a small spa-style ozone generator usually only needs to run for 30 to 60 minutes per day to help keep your water clean. In some cases, it might need to run for 90 minutes or up to two hours once per day. If you don’t have clean water at that point, there is something else going on that we need to troubleshoot.

If you have it set up correctly, run it on a timer as recommended, AND have it turn off at least six to eight hours before people or animals will be in the area, there should be zero issues.

In a cold environment, ozone can persist longer before it breaks down. So what do you do if you open the chest freezer lid or take the cover off of your cold plunge and smell ozone? First, how do you know you are smelling ozone?

Ozone has a very distinctive “clean” smell. People describe it as being similar to chlorine, sweet and pungent, like an electrical spark, or a burning wire. There is a difference between directly smelling ozone and the “clean” smell of items after being exposed to ozone. After ozone breaks down into O2, it has no residual smell.

What To Do If You Smell Ozone

Getting a tiny whiff of ozone generated from a small spa-type ozone generator or hot tub ozone generator will not cause problems for most people. Just step away and let it air out for 30 to 60 seconds or a few minutes. You can turn on a fan if you want.

Make sure that the lid gasket on your cold plunge is sealed well so that ozone does not escape. There are videos on my YouTube channel that show how to get the ozone tube and other power cords and wires inside your chest freezer.

I, along with countless hundreds of others, have used spa-grade ozone generators in our cold plunges since I bought mine in 2018. Some units produce more ozone than others. With a well-sealed lid and a correct setup, I have never once smelled ozone outside of my chest freezer cold plunge when the lid is closed.

Next, always be certain that the ozone tube is connected snugly to the ozone generator. Use a hair dryer or heat gun if the tube needs to be more flexible to push it fully into place.

Also, keep in mind that some materials react with ozone to varying degrees. While ozone machines are used to eliminate odors (cigarettes, smoke from fires, crime scenes, etc.), some materials when exposed to ozone can create a lingering odor. This odor is not ozone but is the smell of the materials that react to ozone.

Ozone, like air, cannot penetrate drywall, wood, or other non-porous surfaces or products. Ozone does not leave a residue because it is a gas. What can be left is anything that has reacted to ozone. Certain fabrics, leather, rubber, and certain plastics do not do well when exposed to ozone.

While ozone can break down chemicals (including VOC’s) it can react with other chemicals in your environment (like formaldehyde in your new furniture, carpet, or building materials), to create additional toxic pollutants.

If you think there is ozone in your home, it is best to ventilate the area and run an air purifier- preferably one with a carbon filter or using PECO technology. These are strategies used in cities with poor air quality.

Also, be aware that some people are highly sensitive to certain chemicals and fragrances. What used to be called “multiple chemical sensitivity” is now referred to as “Idiopathic environmental intolerance (IEI). People with IEI can detect even one molecule of a substance to which they are sensitive even at a distance, and can become incapacitated by the odor. Typical odors include perfumes, fragrances, cleaners, cigarette smoke, air fresheners, pesticides, etc.

If you have any questions about using an ozone generator safely, please let me know.

If you have been using an ozone generator safely in your hot tub, pool, spa, or cold plunge, and have any additional tips please email me, post in my Facebook group, or fill out the contact form on my website.

Comments, questions, and civil discourse are encouraged.

What Ozone Generators to Avoid

These ozone generators do not work well for a chest freezer cold plunge and should be avoided. They will either not keep your water clean or cause a risk to your health:

• Meant for kitchen use (ex. A2Z Ozone’s Aqua 6, Aqua 8, and countless other brands of cheap ozone generators available on Amazon)
• Designed for larger volume hot tubs
• Designed for air purification

Any ozone generator that is not suited for the intended purpose can either produce too much or too little ozone.

Too much ozone in the area around your cold plunge can harm your health when inhaled.

Too little ozone in your water can result in thriving microbes, which can cause skin rashes or worse., such as E. coli infection. This can happen when the ozone generator is undersized by concentration or does not have a strong enough pump.

Ozone not installed correctly (chest freezer not sealed, crimped air hose) or not running correctly (operated too long or at the wrong time), can result in health issues (breathing ozone, or thriving microbes in your water).

What Ozone Generator is Best for Your Chest Freezer Cold Plunge?

There isn’t a single perfect ozone generator for every cold plunge, and I no longer sell ozone units directly to individuals. I was in the business for about six years, and the units I recommended and carried are no longer available. Models and pricing also change often enough that specific brand recommendations in an article like this go out of date quickly.

Instead, here’s what to look for:

• Designed for water, not air
  Choose a spa / pool / water-treatment ozone generator, not a kitchen gadget or room air purifier.
• Sized appropriately for your tub
  For a typical 50–120 gallon cold plunge, look for a small spa-style corona discharge unit with modest output and run time controlled by a timer (for example, roughly 30–60 minutes per day to start).
• Moderate ozone output (concentration)
  For most home cold plunges, something in the range of about 0.05 g/hr of ozone output is usually sufficient when run on a timer. If you go much higher, you increase the risk of off-gassing problems; much lower, and it may not keep up with the bather load.
• Can move ozone into the water effectively
  Either:
  • has an internal air pump strong enough to push ozone through tubing and a diffuser/stone, or
  • is designed to be pulled in through a venturi injector on a circulation line.
• Simple to control with a timer
  A basic on/off control that can be paired with an external timer works fine. You want predictable, repeatable runtime, not something you’re constantly turning on and off manually.

If you use a water-rated unit that meets these criteria, install it correctly, and follow the safety guidelines in this article, you will be in the right ballpark. For current, model-specific advice, you’re always welcome to ask in my Facebook group..