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H1: Professional odour removal and ozone treatment
A landlord in Horfield rang us about a one-bed flat that had been smoked in for twelve years. The tenant had moved out. The landlord had repainted, replaced the carpets, and left the windows open for a fortnight. The flat still smelled like an ashtray.
He’d spent about £400 on paint and carpet. He was about to spend more on new plaster. We told him not to. We ran ozone treatment for 48 hours, followed up with thermal fogging, and the smell was gone. The new paint and carpet stayed. The plaster stayed. Cost him a fraction of what he was planning to spend on ripping the place apart.
That’s what professional odour removal actually does. It doesn’t cover smells up. It breaks down the molecules causing them.
Got a smell that won’t shift? Call us on 07985 505061. We’ll tell you what’s causing it and whether we can fix it.
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Trust Bar
25 years’ experience | £2M insured (AXA) | IICRC certified | Ozone, thermal fogging and hydroxyl treatment
Why Odours Persist (And Why Air Freshener Makes It Worse)
The reason a bad smell comes back after you’ve cleaned, scrubbed, painted, and opened every window is simple. You haven’t reached the molecules causing it.
Odour molecules are tiny. They’re measured in nanometres. They penetrate into porous materials: plaster, concrete, wood, carpet underlay, soft furnishings, insulation, even paint. Once they’re embedded, no amount of surface cleaning will remove them. The smell isn’t sitting on top of the wall. It’s inside it.
Air fresheners, scented candles, odour-neutralising sprays. All they do is add a new smell on top of the old one. Your nose adjusts to the new fragrance within an hour, and the original smell is still there underneath. Plug-in diffusers are the same. They mask. They don’t destroy.
Repainting over a smoke-damaged wall seals in the odour temporarily. Then the paint cures, becomes slightly porous, and the smell comes through again. We’ve seen this dozens of times. People repaint three or four times before they call us, and we still have to treat the wall before the paint will hold the smell back.
Here’s what actually works: you need to reach the same places the odour molecules reached, and you need to break those molecules apart chemically. That’s what ozone, thermal fogging and hydroxyl treatment do. More on each below.
Types of Odours We Eliminate
Not all smells are created equal. Different odour sources produce different compounds, and some are far harder to remove than others.
Death and decomposition
The hardest odour to remove. Decomposition produces a cocktail of compounds including putrescine, cadaverine, hydrogen sulphide, and dozens of volatile organic compounds. These penetrate deep into building materials and can persist for months or years without treatment. We work closely with our trauma cleaning team on these jobs. The biohazard decontamination comes first. The odour treatment follows.
Fire and smoke
Smoke from a house fire contains hundreds of chemical compounds. What burned matters: synthetic materials like plastic, foam and nylon produce particularly stubborn residues. Smoke particles are microscopic and travel through entire properties via air circulation, getting into rooms that weren’t anywhere near the fire. See our fire damage restoration page for the full process. Odour removal is always part of it.
Sewage and drains
Raw sewage contains bacteria, methane, hydrogen sulphide and ammonia. Even after a sewage backup has been cleaned and disinfected, the smell can linger in subfloor materials, behind skirting boards and in wall cavities. Drying alone won’t fix it. The compounds need to be neutralised.
Pet odour
Dog and cat urine soaks through carpet into the underlay and sometimes into the floorboards or concrete beneath. The uric acid crystals are almost impossible to remove with household products. They reactivate with humidity, which is why pet smells are often worse in damp weather. We’ve treated rental properties in Bishopston and St George where the previous tenant’s cats had used the spare bedroom as a litter tray for years. The carpet was replaced. The smell was still coming up from the floorboards.
Damp and musty smells
Persistent damp odour usually signals an underlying moisture problem. We can eliminate the smell, but it’ll come back if the moisture source isn’t addressed. We’ll tell you honestly if you need a damp surveyor before we treat the odour. Sometimes the answer is fixing a leaky gutter or improving ventilation, not running an ozone machine. Our mould removal service often runs alongside damp odour treatment.
Cooking odours
Commercial kitchens, takeaway properties, and homes where heavy cooking (particularly frying) has been done over years. Grease particles carry odour deep into extraction systems, wall surfaces, ceiling tiles and soft furnishings. Curry, fish, deep-frying. They all leave different residues. We’ve treated former takeaway premises on Gloucester Road and Stapleton Road that were being converted to other uses. The food was long gone. The smell wasn’t.
Cannabis and cigarette smoke
Cannabis smoke is oilier than tobacco smoke. It bonds to surfaces differently and is often harder to shift. Cigarette smoke is more pervasive because of the sheer volume people produce over time. Both require treatment beyond the surface. Repainting alone won’t do it.
Our Methods
We don’t use one tool for every job. Different odours and different building materials respond to different treatments. Sometimes we use one method. Often we combine two or three.
Ozone treatment
Ozone (O3) is a powerful oxidiser. An ozone generator converts oxygen in the air into ozone, which reacts with odour-causing molecules and breaks them down into harmless compounds. It reaches everywhere air reaches: into wall cavities, behind furniture, through carpet fibres, inside ductwork.
The property must be completely vacant during treatment. No people, no pets, no plants. Ozone at the concentrations we use is harmful to breathe. Treatment typically runs for 24 to 72 hours depending on severity. After treatment, we ventilate the property thoroughly and check ozone levels have returned to safe limits before anyone re-enters.
Ozone is particularly effective against smoke, decomposition and biological odours. It’s less effective against odours caused by ongoing moisture problems, because the source keeps producing new compounds.
Thermal fogging
A thermal fogger heats a deodorising solution to produce a dense fog of ultra-fine particles. These particles are the same size as smoke particles, so they follow the same paths through a property. Into cracks, joints, wall cavities, fabric weaves, carpet pile. Anywhere smoke went, the fog goes.
We use thermal fogging heavily in fire damage restoration and post-trauma work. It’s also effective as a follow-up to ozone treatment, reaching residual odour in places even ozone may not fully penetrate.
The fog dissipates within a few hours. There’s no residue to clean up.
Hydroxyl generators
Hydroxyl radicals occur naturally in the atmosphere. They’re one of the ways the Earth’s atmosphere cleans itself. Our hydroxyl generators replicate this process indoors, producing hydroxyl radicals that break down odour molecules on contact.
The advantage of hydroxyl over ozone: it’s safe for occupied spaces. People, pets and plants can remain in the building during treatment. This makes it the right choice for situations where full evacuation isn’t practical, such as commercial premises, care homes or multi-unit residential buildings where only one flat is affected.
Hydroxyl treatment is slower than ozone. It typically takes longer to achieve the same result. But for many situations, the ability to keep the space occupied outweighs the extra time.
Our Process
Step 1: Assessment and diagnosis
We visit the property and identify the odour source. This sounds obvious, but it’s the step most people skip. Treating the smell without identifying what’s causing it is a waste of money. Is it smoke residue? A dead animal in a wall cavity? A slow sewage leak under the floor? Rising damp? We need to know before we choose a treatment method.
Sometimes the source is obvious. Sometimes it takes investigation. We’ve found dead rats in loft insulation, leaking waste pipes behind bath panels, and cat urine soaked into concrete subfloor. Once we know what we’re dealing with, we can tell you exactly what treatment will work and what it’ll cost.
Step 2: Source removal
If the odour has a physical source, that has to go first. No amount of ozone will fix a smell if the thing causing it is still there. Contaminated carpet and underlay gets removed. Saturated plasterboard gets taken out. Dead animals get extracted. The source removal is often the hardest part of the job.
Step 3: Treatment
We deploy the appropriate combination of ozone, thermal fogging and hydroxyl treatment based on the odour type, building materials and occupancy situation. For ozone treatment, we seal the property, set up generators, and run them for the required duration. For thermal fogging, we fog systematically room by room. Hydroxyl generators run continuously until the odour is neutralised.
Step 4: Ventilation and verification
After treatment, we ventilate the property and conduct a nose test. Yes, literally. Instruments can measure airborne compounds, but the human nose remains the most sensitive odour detector available. If we can still smell it, we treat again. We don’t sign off until it’s gone.
Step 5: Follow-up
Some odours, particularly decomposition and heavy smoke, can require a second treatment after a few days. The initial treatment breaks down the surface-level molecules, but deeper compounds can continue to off-gas. We build this into our quotes where we think it’s likely. No surprise charges.
Before and After
[Before/after documentation from real odour removal jobs]
Photos and case studies from actual BCH odour removal projects. No stock images.
Honest Talk About What We Can and Can’t Do
In my experience, about 90% of odours can be completely eliminated with the right treatment. The other 10% can be reduced significantly but may never be 100% gone.
Full honesty. Here are the situations where complete elimination is hardest:
- Decomposition that has soaked into concrete subfloor. We can reduce it dramatically, but concrete is porous and deep. Sometimes the slab needs sealing or, in extreme cases, skimming over.
- Smoke damage to unfinished timber. Bare wood absorbs smoke compounds deep into the grain. Treatment helps, but heavily affected timber may need sanding or replacing.
- Pet urine in chipboard flooring. Chipboard swells and breaks down when saturated with urine. Treatment can reduce the smell, but badly damaged chipboard usually needs replacing.
We’ll always tell you upfront if we think complete elimination is unlikely. Better you know before we start than after you’ve paid.
What we won’t do is sell you a treatment we don’t think will work.
Frequently Asked Questions
How much does professional odour removal cost?
It depends on the odour type, the size of the property, and how deep the contamination goes. A single room with moderate smoke smell: £300 to £600. A whole property ozone treatment after a death or fire: £800 to £2,500. Heavy pet odour with underlay and floorboard treatment: £500 to £1,500 per room. We quote after inspection. No ballpark guesses over the phone, because getting it wrong either way doesn’t help you.
How long does ozone treatment take?
The ozone generator typically runs for 24 to 72 hours depending on severity. The property must be vacant during this time. After treatment, we ventilate for several hours before the space is safe to re-enter. Total turnaround for a straightforward ozone job: two to four days. Severe cases involving multiple treatment cycles can take a week.
Is ozone treatment safe?
Ozone at treatment concentrations is not safe to breathe. That’s why the property must be completely empty: no people, no pets, no houseplants. After treatment, we ventilate until ozone levels drop back to safe ambient concentrations. Once we’ve confirmed this, the property is perfectly safe to occupy. Ozone breaks down into ordinary oxygen. It leaves no chemical residue.
Can you remove the smell of death from a house?
Yes. It’s some of the most challenging work we do, but we have a very high success rate with decomposition odour. We use a combination of all three methods: ozone, thermal fogging and hydroxyl treatment. The key is thorough source removal first. Any contaminated building materials need to come out before odour treatment starts. We work alongside our trauma cleaning team on these jobs.
Will painting over smoke damage get rid of the smell?
No. This is one of the most common mistakes we see. Paint seals the smell in temporarily, but standard paint is slightly porous once cured. The odour compounds migrate through and the smell returns within weeks. Even specialist sealant primers (like Zinsser B-I-N) only work after the underlying contamination has been treated. Paint on top of untreated smoke damage is money wasted. Treat first, then paint.
How do you remove pet urine smell from carpets?
If the urine is only in the carpet, we can extract and treat it. If it’s soaked through to the underlay, the underlay needs replacing. If it’s reached the floorboards or concrete, those need treatment too. The uric acid crystals in pet urine reactivate with moisture, which is why the smell seems to come and go. We break those crystals down permanently. A common pattern: people replace the carpet, the new carpet smells fine for a few weeks, then the smell comes back. That’s the subfloor. The carpet was never the problem.
Do you offer odour removal for commercial properties?
Yes. We treat offices, restaurants, retail units, care homes, GP surgeries and rental properties across Bristol. For premises that can’t close during treatment, we use hydroxyl generators, which are safe for occupied spaces. For properties that can be vacated, ozone treatment is typically faster and more thorough. We’ve treated commercial kitchens on Whiteladies Road, office spaces in Temple Quarter, and rental flats across BS1 to BS16.
Related Services
- Fire Damage Restoration — Smoke and soot removal with full odour treatment
- Trauma Cleaning — Biohazard decontamination followed by decomposition odour removal
- Deep Cleaning and Disinfection — Full property sanitisation, often paired with odour treatment
- Flood Damage Cleaning — Damp, mould and sewage odour treatment after flooding
Get Rid of the Smell. For Good.
Air fresheners are a sticking plaster. We’re the surgery.
If you’ve got a smell that cleaning, painting and ventilation haven’t fixed, it needs professional treatment. We’ll visit, identify the source, and give you a straight answer about what it’ll take.
We’re at 290-294 Southmead Road, Bristol BS10 5EN. We cover all of Bristol, Bath, South Gloucestershire and North Somerset.
Phone: 07985 505061 WhatsApp: 07985 505061 Email: hello@bristolcleaningheroes.co.uk
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