By Anton van den Brand · Founder Shoefresh · July 2026
You see it more and more often: shoe dryers with an "ozone function" or "active oxygen." But what does that actually mean? And more importantly: is it safe?
As the founder of Shoefresh, I've been working with ozone technology in shoe dryers for over 12 years. In this article, I explain what active oxygen is, how it works in a shoe dryer, and what the safety standards say about it.
What is Active Oxygen (Ozone)?
Active oxygen — also known as ozone (O₃) — is an activated form of oxygen. While regular oxygen (O₂) consists of two atoms, ozone has three. That third atom is unstable and actively seeks out other molecules to bind with.
This property makes ozone a natural cleaning agent. It has been used for decades in drinking water purification, the food industry, and the medical sector. Not with chemicals, but through a natural process.
In a shoe dryer, the same principle is applied: ozone targets the bacteria and fungi that produce odor-causing smells.
How Does Ozone Work in a Shoe Dryer?
A shoe dryer with an ozone function has a built-in ozone generator. This converts regular oxygen from the air into ozone. The ozone is then blown through the shoe together with warm air.
Here's how it works step by step:
- Cleaning — The ozone flows through the entire interior of the shoe and binds to odor molecules. These are oxidized and neutralized. Bacteria and fungi that cause the odor are targeted.
- Drying — Simultaneously, warm air safely dries the shoe from the inside out. Moisture is the breeding ground for bacteria. By drying, you remove it.
- Decomposition — After cleaning, ozone breaks down within minutes back into regular oxygen (O₂). Nothing remains in your shoe or in the room.
The result: fresh, dry shoes without chemicals, sprays, or refills.
Is Ozone in a Shoe Dryer Safe?
This is the question I'm asked most often — and rightfully so. Ozone is a powerful agent, so it makes sense to want to know if it's safe to use at home.
The short answer: yes, provided the device is properly designed and CE-certified.
The Shoefresh Opod generates only a minimal amount of ozone per hour, and only during the short cleaning cycle. It is CE-certified and meets the strictest European standards. The ozone released is minimal and quickly breaks down back into oxygen. There are no health risks with normal use.
Tip: Place your shoe dryer in a well-ventilated space such as a utility room, garage, or hallway.
"I developed my first prototype with ozone technology in 2013. Since then, we've continuously refined the system. The amount of ozone we use is just enough to be effective, without ever posing a problem for the user or the environment."
— Anton van den Brand, Founder Shoefresh
Ozone Function vs. Shoe Dryer Without Ozone
Not every shoe dryer has an ozone function. What do you miss when it's absent?
| With ozone function | Without ozone function | |
|---|---|---|
| Drying | ✅ Yes | ✅ Yes |
| Targeting bacteria and fungi | ✅ Yes | ❌ No |
| Fighting odor at the source | ✅ Yes | ❌ Only removes moisture |
| Refills needed | ❌ No | Sometimes (sprays) |
| Shoes stay fresh longer | ✅ Yes | ❌ Odor returns faster |
A shoe dryer without ozone dries your shoes well, but doesn't address the cause of the smell. Bacteria and fungi survive and start multiplying again at the next use. You'll notice the difference especially in the long run.
Ozone vs. shoe spray: A spray temporarily masks odors. Ozone targets the source — the bacteria and fungi that produce the smell. Plus, with ozone you don't need refills or extra costs.
Do You Need Refills?
No. A shoe dryer with an ozone function generates the active oxygen itself, with a built-in ozone generator. You don't need to refill, replace, or reorder anything.
This also makes it environmentally friendly: no disposable products, no packaging, no chemicals. Just oxygen from the air that returns to regular oxygen after use.
Frequently Asked Questions About Ozone in Shoe Dryers
What exactly is active oxygen?
Active oxygen is another name for ozone (O₃). It's an activated form of oxygen that oxidizes odor molecules and targets bacteria and fungi. It's used in drinking water purification and the medical sector, among other applications.
Is ozone harmful to my shoes?
No. The amount of ozone a shoe dryer uses is minimal and safe for all materials. It actually extends the lifespan of your shoes by targeting bacteria and fungi before they cause damage.
Does ozone have a smell?
Ozone has a light, fresh scent that some people recognize as "the smell after a thunderstorm." With a shoe dryer, the amount is so small you'll barely notice it. Within a few minutes after the program, the scent is completely gone.
Does ozone work with all types of shoes?
Yes. Ozone is suitable for all materials, from athletic shoes to leather. With the Shoefresh Opod, you choose the program that matches the material: SPORT (60°C) for wet athletic shoes, SNEAKER (60°C) for lightly damp shoes, and LEATHER (40°C) for leather and delicate materials.
Is ozone safe to use at home?
Yes, when using a CE-certified device like the Shoefresh Opod. The amount of ozone generated is minimal and well within European safety standards. Place the shoe dryer in a well-ventilated space for optimal use.
Want to know which shoe dryer suits you? Read our complete guide to shoe dryers.