A House with Six Cats: Urine Odour Soaked into Carpet and Walls, Relatives Stopped Visiting, and Ripping Out Every Carpet Did Not Fix It
Last updated: 6 Sep 2026 | 11 Views |
Ozone disinfection service 2026 for homes with pets
A House with Six Cats: Urine Odour Soaked into Carpet and Walls, Relatives Stopped Visiting, and Ripping Out Every Carpet Did Not Fix It
Why cat urine is the hardest odour of all to remove, and why ripping out the carpet does not solve it.
Cat owners cannot smell their own house, while anyone walking in smells it the moment the door opens. That gap is why this problem drags on for years without the owner knowing where to start.
Cat urine odour is unlike any other, because cat urine contains compounds that crystallise as it dries into a substance that does not dissolve in water — and that substance releases odour again every time it meets humidity.
Which means that in the rainy season, or on any humid day, an odour you thought was gone comes back at full strength, however many times that spot has been mopped and wiped.
This article tells the true story of a home with six cats that took two years to resolve, explains why ripping out the carpet is not enough, and what ozone treatment — a gas that reaches wherever air reaches — does about it.
The story
A house full of love, and an odour the owner could not smell
Kanchana keeps six cats in a two-storey house in Nonthaburi. All the cats are well cared for, with five litter trays around the house, litter changed daily, and all of them neutered.
But over the past two years the oldest male cat had begun occasionally urinating outside the tray, particularly in room corners and behind the sofa — behaviour that appears as cats age or become stressed.
Kanchana cleaned up every time she found it, using a pet odour remover bought from a pet supply shop.
She smelled nothing particular in the house — until her sister visited and said plainly that the house smelled strongly of cat. That was the first she knew there was a problem.
What she did, and the cost that piled up
Kanchana started by ripping out the carpet in the living room and upstairs bedrooms entirely, assuming the odour was in the carpet. Removal and new flooring came to about 58,000 baht.
The smell was noticeably weaker for two weeks, then came back in the second month — particularly on rainy, humid days.
So she replaced the sofa, threw out the old chair cushions, washed every curtain in the house and repainted the downstairs walls — another 90,000 baht or so.
The result was the same: temporary improvement, then return. And over those two years, relatives who used to visit regularly came less and less until they barely came at all — which upset her far more than the money.
Why it came back every time it rained
When Kanchana consulted the vet who looks after her cats, it was the vet who explained this to her for the first time.
Cat urine contains a higher proportion of uric acid than other animals'. As the urine dries, that uric acid crystallises into salts that do not dissolve in water — which is why wiping with water and ordinary cleaners removes the liquid but leaves the crystals.
When humidity rises, as on a rainy day, those crystals absorb moisture and release the odour again — which explains why the smell returns in cycles with the weather.
The vet also pointed out that urine that has soaked into floor joints, grout, the lower part of walls and the timber beneath the floor remains even after the carpet has been removed — which explains why replacing the flooring was not enough.
What the animal hospital recommended
The same vet suggested Kanchana try ozone treatment, mentioning that the animal hospital itself uses it on rooms with odour problems and on kennels after infectious cases.
The reason it works on pet odour is that ozone does not wash the substance away like water. It reacts by oxidation directly with the molecules causing the odour — including those locked in crystals that water cannot dissolve.
And because ozone is a gas, it reaches floor joints, grout, the lower walls, behind cabinets, under sofas and into the air conditioning system — every place urine has soaked into and no cloth can reach.
Kanchana boarded all six cats at the animal hospital for a day and had the whole house treated, cycles of about thirty minutes covering every room, the bathrooms and the air conditioning, then ventilated. When she brought the cats home that evening, the smell was completely gone.
What it actually costs
Homeowners cannot smell their own house
The human nose adapts to a continuously present odour within minutes, so a pet owner is the last person to know there is a problem — and usually finds out from an uncomfortable remark by someone else.
The smell returns every time humidity rises
Uric acid crystals from cat urine absorb moisture and release odour again, so a smell you thought had gone returns at full strength every time it rains — leaving the owner unsure whether it can be fixed at all.
Relatives and friends stop visiting without saying why
Most people will not mention someone else's house smelling. They simply visit less — a loss the owner feels but cannot connect to a cause.
Money spent repeatedly without touching the cause
Kanchana spent 58,000 baht ripping out carpet and laying new flooring, then 90,000 baht on a new sofa, discarded cushions, washed curtains and repainting — nearly 150,000 baht in two years, and the smell still came back.
Why the usual fixes fail
Ripping out the carpet and laying new flooring
Removing carpet genuinely helps, because carpet is a major reservoir. But urine that has soaked into floor joints, grout and the timber beneath remains, and releases odour through the new floor in the second month.
Wiping with a pet odour remover
These products work well on fresh urine that has not yet dried. Against dried, crystallised uric acid, surface wiping removes only the top layer while what has soaked deeper stays.
Replacing the sofa and discarding old cushions
Replacing visibly stained furniture is worth doing. But if the other sources in the house remain, a new sofa begins absorbing odour from the household air within weeks.
Repainting the downstairs walls
Urine that soaked into the lower walls sits beneath the original paint. Painting over simply covers it, and the odour permeates through the new coat when humidity rises — exactly as with cigarette smoke.
Air purifiers and air fresheners
An air purifier filters particles but does nothing about a source releasing odour continuously. Fresheners add a new smell on top of the old one, which visitors detect immediately and usually find worse.
Why ozone handles pet odour differently from cleaning
The fundamental difference is that wiping and washing work by dissolving and carrying substances away, which works for water-soluble compounds. Uric acid crystals from cat urine are not water-soluble, so they remain after cleaning.
Ozone works differently. It does not carry anything away; it reacts by oxidation directly with the molecule until its structure changes and it no longer smells — which works on water-insoluble substances too.
And because ozone is a gas, it penetrates floor joints, grout, lower walls, behind cabinets, under sofas, into curtain fabric and into the air conditioning system — everywhere urine can reach. This service uses the Master Ozone Generator, the only brand in Thailand certified by the Department of Medical Sciences, Ministry of Public Health, and tested by Intertek in the UK.
10 reasons the AIROFOG U260 solves it
1. It reacts with substances water cannot dissolve
This is the main reason ozone handles cat urine differently from cleaning: uric acid crystals do not dissolve in water, so washing cannot carry them away, while ozone reacts with the molecules directly.
2. It reaches floor joints, grout and lower walls
Urine soaks into joints and crevices no cloth can reach. Ozone, as a gas, penetrates wherever air reaches — including all of them.
3. It treats behind cabinets, under sofas and the corners cats favour
Cats urinating outside the tray choose enclosed corners and the space behind furniture — the hardest places for an owner to clean. Treating the whole house covers those without moving any furniture.
4. It reaches the air conditioning that circulates the odour
The air conditioning draws in air carrying odour molecules and distributes it throughout the house every day. Treating with the unit on recirculation lets ozone deal with the system too — a place nobody cleans.
5. No chemical residue for a pet to lick
Ozone reverts to oxygen after reacting, so there is no chemical residue on floors or furniture that an animal might lick or lie on — a serious concern for pet owners.
6. It adds no humidity, which is what triggers the odour
Humidity is what makes the crystals release odour again, so washing floors with water actually triggers the smell in the short term. Ozone is a gas and adds none.
7. No need to rip out more flooring or discard more furniture
Many owners throw a great deal away before learning there is another approach. Ozone treats what is still in the house, far cheaper than replacing it.
8. It works on every pet odour, not just cat urine
Dog odour, bird cages, litter trays and the smell of a sick animal are all handled by the same principle, so a multi-pet household is dealt with in one treatment.
9. About 30 minutes per cycle, with pets boarded for one day
The treatment runs about thirty minutes per cycle, then the house is ventilated until the ozone smell has gone. Pets must be out during treatment, but come home the same evening.
10. It costs less than re-flooring one room
Kanchana paid 58,000 baht to rip out carpet and lay new flooring, and the smell came back. Treating the whole house costs far less — and on bookings of 15,000 baht or more you also receive a free CHEMGENE HLD4H disinfection spray service.
Before and after
Before
- Six cats, five litter trays, litter changed daily, all neutered
- An older male cat occasionally urinating in corners and behind the sofa
- The owner unable to smell it, until her sister said plainly that the house smelled strongly
- Carpet ripped out and new flooring laid — 58,000 baht; smell weaker for 2 weeks then back
- New sofa, discarded cushions, washed curtains and repainting — another 90,000 baht
- The smell returning strongly every time it rained, and relatives who used to visit barely coming at all
After
- Understanding that uric acid crystals from cat urine do not dissolve in water, so cleaning cannot remove them
- All six cats boarded at the animal hospital for one day
- The whole house ozone-treated, every room plus bathrooms and the air conditioning, about 30 minutes per cycle
- Ozone reaching floor joints, grout, lower walls, behind cabinets and under the sofa
- Cats home the same evening, with the smell completely gone
- Still gone on rainy, humid days — the real test
How we get you started, in 3 steps
1. Survey the house and find where the animals actually go
We look at the size of the house, the number of rooms, the floor and wall materials, where the litter trays are, and the spots the owner has noticed the animals using outside the tray — to set exposure time and the order of rooms.
2. Move the pets out and run the treatment
Pets and people must be out of the house during treatment. Most owners board their animals at a vet or a boarding facility for the day. The house is then sealed, the air conditioning set to recirculate so ozone reaches the system, and the treatment runs at about 30 minutes per cycle.
3. Ventilate and test on a humid day
Doors and windows are opened until the ozone smell has gone and the pets can come home. The real test is a rainy or humid day, because that is the condition that makes any remaining crystals release odour. No smell on that day means it has genuinely been dealt with.
What a customer says
“I ripped out every carpet, laid new flooring, replaced the sofa, repainted — nearly 150,000 baht — and every time it rained the smell came straight back. It was the vet who explained that cat urine contains uric acid that crystallises and does not dissolve in water, so no amount of washing removes it; you need something that reacts with it directly. One day of ozone treatment and it was done, and it has not returned through several rainy spells since.”
Kanchana — Owner of six cats, Nonthaburi
Why cat urine differs from every other pet odour
All animal urine contains waste from protein metabolism, but different species excrete it in different forms. Humans and dogs excrete most of it as urea, which dissolves readily in water.
Cats evolved from desert-dwelling ancestors, so their bodies conserve water and produce more concentrated urine, with a higher proportion of uric acid and related compounds than other pets.
As the urine dries, the urea component breaks down and partly evaporates, but the remaining crystals do not dissolve in water — so wiping with water and ordinary cleaners cannot carry them away, and those crystals absorb moisture and release odour again whenever the air is humid.
That is the chemical reason cat urine is the hardest household odour to remove, and why a method that reacts with the molecules directly works better than one relying on dissolving and washing away.
Homes with pets, and the thing guests never say
Socially, telling a homeowner that their house smells is something most people will not do, because it is delicate and risks the relationship.
What happens instead is that guests gradually visit less, suggest meeting out instead, or find other reasons to decline — which the owner feels but usually reads as everyone simply being busy.
Meanwhile the owner cannot smell it themselves, because their nose has adapted, so there is no way to know there is a problem until someone finally says it — which can take years.
The simplest check is to leave the house for at least thirty minutes of fresh air and then walk back in paying deliberate attention to the first breath, or ask someone you trust to be honest. Every pet owner should do this once a year.
Frequently asked questions
Do the pets have to leave the house?
Yes, during treatment and the ventilation period. Most owners board them at a vet or boarding facility for the day and bring them home the same evening once ventilation is complete.
Is there any residue afterwards that a pet might lick?
No. Ozone reverts to oxygen after reacting, so there is no chemical residue on floors, furniture or pet bedding — a significant advantage over many chemical products.
Do we need to rip out flooring or replace furniture first?
In most cases no. Ozone treats what is still in the house, except for materials so saturated they are physically damaged — such as cushions soaked repeatedly until they have degraded. We will tell you at survey.
Will the smell come back when it rains?
Not if the ozone has reached the places where crystals accumulated and reacted with them. That is why we recommend testing on a humid day — it is the real test of whether everything has been reached.
Should we treat if the cat is still urinating outside the tray?
You should address the cat's behaviour and health alongside, because urinating outside the tray usually has a health or stress cause. We recommend consulting a vet in parallel, or the problem will simply recur.
Does it work on dog odour and bird cages?
On all of them. Dog odour, bird cages, litter trays and the smell of a sick animal are handled by the same principle, so a multi-pet household is dealt with in a single treatment.
How long does it take?
About 30 minutes per cycle, with the number of cycles depending on the size of the house, then ventilation until the ozone smell has gone. Most homes are finished within a single day.
What does it cost?
It depends on the size of the house and the severity of the odour. Send us the house size, number of rooms and details of the problem for an assessment — and on bookings of 15,000 baht or more you receive a free CHEMGENE HLD4H disinfection spray service.
If the smell returns every time it rains, you have not actually dealt with it
Kanchana spent nearly 150,000 baht over two years ripping out carpet, laying new floors, replacing the sofa and repainting — and the smell returned every time it rained, because those methods rely on washing away a substance that cannot be washed away.
Ozone treatment reacts with the odour molecules directly, reaches floor joints, grout, lower walls and the air conditioning, adds no humidity to trigger the smell, and leaves no residue for a pet to lick.
If your home has pets and an odour that returns in cycles, send us the house size, the number of rooms and the problem areas, and we will assess how many cycles it needs and how long it will take.
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