Ozone Treatment for Odour Removal: How It Works and When to Use It

I get asked about ozone at least twice a week. Landlords who can’t shift a smell. Property managers with a flat that’s been smoked in for years. Families who’ve had a flood and the damp smell won’t go away.

“Does that ozone thing actually work?”

Short answer: yes, for the right problems. Long answer: read on.

How Ozone Works

Ozone is O₃. Three oxygen atoms instead of the usual two. That third atom is unstable. It wants to break away and attach to something else.

When ozone meets an odour molecule, that extra oxygen atom breaks off and bonds with the molecule, changing its chemical structure. The odour molecule is oxidised. Destroyed, essentially. It’s not masked or covered up. It’s chemically altered so it no longer smells.

This is the same process that happens naturally during thunderstorms. That fresh, clean smell after lightning? That’s ozone doing its thing at a smaller scale.

We generate ozone artificially using commercial ozone generators. These machines take oxygen from the air and pass it through a high-voltage electrical discharge (corona discharge) or UV light to create O₃. The ozone fills the room, contacts every surface, and gets into places that physical cleaning can’t reach.

Into fabrics. Into carpet pile. Into the pores of brick and plaster. Behind skirting boards. Inside cupboards. Everywhere the air goes, the ozone goes.

That’s what makes it so effective. You can’t physically scrub the inside of a wall cavity. But ozone gas can reach it.

What Ozone Eliminates

Ozone works on odours caused by organic compounds. That covers most of the stubborn smells we deal with.

Cigarette and tobacco smoke. Thirdhand smoke residue causes persistent odour that soaking into walls, ceilings, and fabrics over years. Ozone oxidises the nicotine and tar compounds responsible.

Cannabis smell. The terpenes in cannabis are organic compounds. Ozone breaks them down effectively.

Pet odours. Urine, dander, general animal smell. Particularly effective on cat urine, which contains uric acid crystals that are notoriously hard to eliminate any other way.

Decomposition odours. The compounds produced during decomposition - putrescine, cadaverine, and others - are organic molecules that ozone oxidises. This is one of the most important applications. Nothing else truly removes the smell of death from a property.

Fire and smoke damage. Smoke particles and soot residues contain organic compounds. Ozone treatment after thorough cleaning removes the lingering smoke smell.

Cooking odours. Curry, fish, fried food - years of cooking smells embedded in a kitchen. Ozone breaks down the fat-based compounds.

Damp and mould. The musty smell from mould (caused by microbial volatile organic compounds, or MVOCs) responds well to ozone treatment. Though you need to fix the moisture source and remove the mould itself too, or the smell comes back.

Sewage. Hydrogen sulphide and other sulphur compounds from sewage contamination. Ozone oxidises these efficiently.

Honestly, I’ve yet to meet an organic odour that ozone can’t handle. The question is always whether the source has been removed first. Ozone treats the residual smell. It doesn’t fix the cause.

The Process

Ozone treatment isn’t complicated, but it needs doing properly. Here’s how we run it.

1. Source removal first. This is the most important step and it happens before the ozone machine even comes out of the van. Whatever caused the smell needs addressing. Clean up the contamination. Remove spoiled materials. Treat the mould. Strip the smoke-damaged surfaces. If you skip this step and just run ozone, the smell comes back within days.

2. Clean all accessible surfaces. Thorough cleaning with appropriate products before ozone treatment. This removes the bulk of odour-causing material. Ozone then handles what cleaning can’t reach.

3. Prepare the space. Remove all people, pets, and plants. Ozone in the concentrations we use is harmful to breathe. This isn’t a treatment you do while people are in the building.

Remove or protect sensitive items. Ozone can degrade rubber seals, certain plastics, and some electronics over extended exposure. We assess each property individually.

4. Seal the space. Close all windows and doors. Seal gaps with tape if necessary. Block ventilation openings. The ozone needs to build up to effective concentration levels within the space. Any leakage reduces effectiveness and wastes time.

5. Run the generator. We position one or more commercial ozone generators depending on the size of the space. These aren’t the small domestic units you can buy online for £50. Our machines produce significantly higher ozone concentrations.

The generators run continuously, cycling ozone through the space. We often use fans to circulate the ozone evenly.

Treatment duration varies:

• Mild odours (cooking, light pet): 2-4 hours
• Moderate odours (smoke, cannabis): 6-12 hours
• Severe odours (decomposition, fire damage): 12-24 hours
• Extreme cases: multiple 24-hour treatments with surface cleaning between rounds

We’ve run 3 consecutive 24-hour cycles on a property in Bishopston where a heavy smoker had lived for 30 years. That was an extreme case. Most jobs are done in a single treatment.

6. Ventilate. After treatment, the property must be thoroughly ventilated before anyone enters. We open all windows and doors and allow at least 2 hours for ozone levels to dissipate to safe levels. Ozone breaks down naturally back to O₂, but this takes time.

7. Assessment. We return after ventilation to check results. Our noses are calibrated by 25 years of experience. If there’s residual odour, we determine whether another treatment round is needed or if there’s a source that wasn’t fully addressed.

Limitations

Ozone isn’t magic. It has real limitations that anyone selling the service should be honest about.

It doesn’t remove the source. If there’s a dead animal in the wall cavity, ozone will temporarily reduce the smell, but it’ll return. The source must be found and removed. We always investigate the cause before treating the symptom.

Heavy contamination needs physical cleaning first. A room with nicotine-yellowed walls needs washing down with TSP or equivalent before ozone treatment. Running ozone on thick surface contamination is like trying to freshen up a rubbish tip with air freshener. Deal with the bulk first, then use ozone for what’s left.

It won’t work on non-organic odours. Chemical smells from new paint, fresh carpet adhesive, or manufactured materials aren’t effectively treated with ozone. These are VOCs that dissipate over time naturally but don’t respond well to oxidation.

Some materials absorb and hold odour so deeply that ozone alone isn’t enough. Thick underlay beneath carpets in a smoker’s house, for example. Sometimes the material simply has to go. No amount of ozone will fix a carpet pad that’s saturated with 20 years of cigarette smoke.

Repeat treatments. Severe contamination occasionally needs 2-3 rounds. This adds cost and time. We’re upfront about this likelihood during the initial assessment.

Safety. Ozone is an irritant and toxic at the concentrations we use for treatment. Nobody can be in the property during treatment. This means the property is out of use for the treatment period plus ventilation time. For landlords, that’s another day or two of void period.

Cost

Ozone treatment on its own (without additional cleaning) typically runs £200-600 depending on the property size and treatment duration needed. As part of a full odour removal service including source treatment, cleaning, and ozone, costs range from £500 to several thousand.

We always quote after seeing the property. The severity and source of the odour determine the approach and cost.

Need stubborn odours removed from a property in Bristol? Call 07985 505061 or email hello@bristolcleaningheroes.co.uk. We’ll assess the problem and give you a straight answer about whether ozone treatment is the right solution.