A Rental Condo Soaked in the Previous Tenant's Cigarette Smell: Empty for Four Months and 76,000 Baht of Lost Rent
Last updated: 6 Sep 2026 | 8 Views |
Ozone disinfection service 2026 for condos and rental units
A Rental Condo Soaked in the Previous Tenant's Cigarette Smell: Empty for Four Months and 76,000 Baht of Lost Rent
Why cigarette smell survives a fresh coat of paint, and what ozone does that cleaning cannot.
Cigarette smell that has soaked into a room is not just on the walls. It is in the curtains, the sofa foam, the gaps in built-in wardrobes, the air conditioning ducts and the bathroom grout. That is why repainting and servicing the air conditioning does not remove it — and why one condo in Ratchada sat empty for four full months.
Almost every landlord has had the same experience. The previous tenant moves out, you open the door and the smell hits you immediately. You hire a deep-cleaning crew, service the air conditioning, wash the curtains and repaint the whole unit.
Then two weeks later you go back and open the door. The smell is still there. Fainter, perhaps, but there. And it comes back at full strength every time the unit has been shut up for a few days.
This article explains why cigarette smell is harder to remove than any other odour, and why ozone treatment does what cleaning cannot — along with the true story of a landlord who lost 76,000 baht in rent before finding the answer.
The story
The previous tenant lived there three years, and smoked indoors for three years
Manat owns two rental condo units in Ratchadaphisek: thirty-two square metres, one bedroom, let at 19,000 baht a month, the market rate for that location.
The previous tenant stayed three full years, paid on time every month, never caused a single problem, and left on good terms when their job relocated. The one thing Manat did not know was that they had smoked indoors for all three years.
The day he took the unit back he opened the door and knew immediately there was a problem. It was not fresh smoke. It was a sour, sweetish stale smell embedded in everything in the room — even inside the closed built-in wardrobe.
The white walls had turned a faint yellowish cream across the whole unit, with no obviously dirty patch anywhere. And when he ran a hand along the wall near the air conditioning vent, a thin sticky film came away on his fingertips.
38,000 baht spent, and the smell still there
Manat did what most people do. He hired a deep-cleaning crew twice, had the air conditioning fully stripped and cleaned, washed both sets of curtains, scrubbed the floors and bathroom grout, and repainted the whole unit twice.
That came to 38,000 baht, and he left the unit with the windows open for another week before going back.
When he returned and opened the door, the smell was still there. Clearly fainter, but immediately noticeable on entry, especially in the bedroom corner and inside the built-in wardrobe.
Worse, when he closed the unit up and ran the air conditioning for thirty minutes as a test, the smell came back almost to its original strength — because the air conditioning was drawing air from walls and ceiling that still held residue and circulating it.
Four months unlettable, and eleven viewers who walked away
Over those four months, eleven prospective tenants came to view. Every one of them liked the location, liked the price, and liked the unit from the photographs.
But nine of the eleven said the same thing within the first thirty seconds of walking in: had someone been smoking in this unit?
The other two said nothing at all and never made contact again. The agent showing the unit told Manat plainly that this kind of smell is very hard to let, because anyone renting a condo immediately thinks about their own clothes and belongings picking it up.
Four months of lost rent came to 76,000 baht, plus common area fees still payable, plus the 38,000 baht already spent on cleaning and paint — over 100,000 baht of damage from a single unit.
The answer came from a different agent
Another agent Manat spoke to asked the question that went straight to the point: had he tried ozone treatment?
That agent explained that three other units in the same building with cigarette smell problems had all been solved this way, and those owners had let their units within two to three weeks of the treatment.
The reason it works is not that ozone masks the smell. It is that ozone is a gas, so it penetrates everywhere air reaches — into curtain fabric, sofa foam, the gaps in built-in wardrobes, the air conditioning ducts and the pores of the wall — and reacts directly with the odour molecules.
Manat booked an ozone treatment. The process took around thirty minutes per cycle on an automatic timer, then the unit was ventilated. When he went back the next day, the smell was completely gone, including inside the built-in wardrobe.
What it actually costs
A unit with a smell does not let slowly — it does not let at all
Condo tenants decide in the first thirty seconds. Smell is the one thing that makes someone who likes both the location and the price walk straight out, and no discount compensates for it in a tenant's mind.
Lost rent always costs more than the repairs
Manat spent 38,000 baht on cleaning and paint, but lost 76,000 baht in rent — which means the vacancy, not the repair, is the main cost.
The smell comes back stronger every time the unit is shut up
This is what confuses landlords most. A unit with the windows open seems fine, but shut it up and run the air conditioning and the smell returns, because residue is still in the walls, the ceiling and the air system.
Tenants fear their own clothes and belongings will pick it up
People reject a unit with cigarette smell not merely because it is unpleasant, but because they fear the smell transferring to their clothes, their bedding and themselves when they go out — a reasonable concern.
Why the usual fixes fail
Repainting the whole unit
Fresh paint covers the yellowing and does reduce the smell somewhat. But smoke residue has soaked into the old paint layer, the plaster, the ceiling and every gap paint cannot reach, so the smell comes back through the new coat within weeks.
Fully stripping and cleaning the air conditioning
Servicing the air conditioning is genuinely necessary and helps. But it addresses the coil and the filter, while residue sits in the ductwork, the casing and the insulation, which cannot be stripped out. Run the unit and the smell circulates again.
Washing curtains and deep cleaning
Washing curtains and scrubbing floors handles reachable surfaces. It does not handle sofa foam, mattresses, the gaps in built-in wardrobes, the space behind the refrigerator, or the void above the false ceiling — where the smell accumulates most.
Air fresheners, charcoal and baking soda
Air fresheners mask the smell for a few hours before the original returns. Charcoal and baking soda absorb only odour molecules already floating in the air near them; they do nothing about residue embedded in materials.
Leaving the windows open for a week
Ventilation reduces the smell in the air, but it does not pull residue out of walls, upholstery and ductwork. Shut the unit again and the residue slowly evaporates back into the air.
Why ozone does what cleaning cannot
The crucial difference is that cleaning treats surfaces you can reach with a hand or a cloth, while ozone is a gas that penetrates everywhere air reaches — into fabric, into foam, into cabinet gaps, into ductwork, and into the pores of the wall.
Ozone, or O₃, does not mask an odour with another odour. It reacts by oxidation directly with the molecules that cause the smell, altering their structure so they no longer smell. Once it has reacted, ozone breaks back down into ordinary oxygen, O₂, leaving no residue.
World Health Disinfection's ozone 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, confirming 99.99 per cent effectiveness against mould.
10 reasons the AIROFOG U260 solves it
1. Ozone is a gas, so it reaches wherever air reaches
This is the fundamental difference from wiping and spraying. A gas penetrates curtain fabric, sofa foam, closed built-in wardrobes, air conditioning ducts and the pores of a wall — which is where cigarette smell actually accumulates.
2. It destroys odour molecules rather than covering them
Air fresheners add a new smell on top of the old one. Ozone oxidises the odour molecules until their structure changes and they no longer smell — which is why the smell does not return when the unit is closed up.
3. It breaks down back into oxygen, leaving no residue
After reacting, ozone naturally reverts to oxygen. There is no chemical residue on surfaces, nothing to wipe down, and a new tenant can move in without any concern about chemicals.
4. It adds no humidity to the room
Unlike steam treatment or liquid spraying, ozone treatment does not raise the humidity — which matters greatly for a condo that sits closed up, because added moisture is where the next problem, mould, begins.
5. It handles mould in the air conditioning and furniture at the same time
A unit closed up for a long time usually has both cigarette smell and mould in the air conditioning. The Master Ozone Generator is certified by the Department of Medical Sciences as removing deep-seated mould in air conditioning and furniture to 99.99 per cent.
6. It takes about 30 minutes per cycle
The automatic timer completes the process in around thirty minutes, after which the space is ventilated until the ozone smell is gone. The unit can be shown the same day or the next — not closed up for a week.
7. No need to remove furniture or repaint
Ozone treatment works on a fully furnished unit. Nothing has to be moved out, built-in units do not have to be stripped, and in many cases no repainting is needed — far cheaper than what landlords usually try first.
8. Certified by the Department of Medical Sciences and Intertek
The Master Ozone Generator is the only brand in Thailand tested by the Department of Medical Sciences, Ministry of Public Health, and by Intertek in the UK — something you can show a tenant or a building committee.
9. It works on every smell embedded in a room, not just cigarettes
Damp and musty smells, food, sweat, pets, paint and chemical odours are all handled by the same principle, so a unit with several smells mixed together is dealt with in one treatment.
10. It costs a fraction of one month's lost rent
Against 19,000 baht a month of lost rent, one ozone treatment is a small fraction. And on bookings of 15,000 baht or more you also receive a free medical-grade disinfection spray service using CHEMGENE HLD4H.
Before and after
Before
- The previous tenant smoked indoors continuously for 3 years
- Two deep cleans, a full air conditioning strip-down, washed curtains and two coats of new paint
- 38,000 baht already spent, and the smell returning every time the unit was closed with the air conditioning on
- 11 people viewed the unit; 9 asked about cigarette smell within the first 30 seconds
- Empty for 4 months, 76,000 baht of lost rent plus common area fees still payable
- Over 100,000 baht of total damage from a single unit
After
- The whole unit treated with ozone, with no furniture removed and no repainting
- Ozone reaching curtains, upholstery, built-in wardrobe gaps, ductwork and wall pores
- About 30 minutes per cycle, then ventilation until the ozone smell had gone
- The smell completely gone, including inside the built-in wardrobe, and not returning when closed up
- Let within two weeks of treatment, at the original market rent
- Certification documents from the Department of Medical Sciences and Intertek available to show tenants
How we get you started, in 3 steps
1. Survey and assess the space
We look at the size of the unit, the number of rooms, the furniture and materials, the air conditioning system, and how severe the odour or contamination is, in order to set the correct ozone exposure time. An ordinary room can be assessed and started immediately; a space with mould or viral contamination is checked for contamination level first.
2. Prepare the environment and run the treatment
The space is sealed and everyone leaves the area to prevent ozone escaping, then the treatment runs for the set time. The automatic timer completes the process in around 30 minutes. Where mould or virus is present, surfaces are disinfected first and the ozone treatment follows immediately.
3. Ventilate and verify
When the process finishes, doors and windows are opened to clear any remaining ozone smell, after which the space returns to normal use. Where surface mould was present, we check surface moisture levels to confirm no mould remains.
What a customer says
“I repainted twice, serviced the air conditioning, washed the curtains — 38,000 baht — and the smell still came back every time I closed the unit and ran the air conditioning. It sat empty four months and cost me 76,000 baht in rent. Eleven people viewed it and nine asked about cigarette smell as they walked in. One ozone treatment and the smell was gone, even inside the built-in wardrobe, and it let within two weeks.”
Manat — Condo landlord, Ratchadaphisek, Bangkok
Why cigarette smell is harder to remove than any other odour
Cigarette smoke is not simply a smell. It is an aerosol of thousands of compounds, part gaseous and part oily. It is the oily part that clings to surfaces and soaks into materials.
When someone smokes in a closed room over a long period, that oily residue builds as a thin layer across every surface — including surfaces nobody sees: the top of the false ceiling, the back of cabinets, the inside of air conditioning ducts and the pores of plastered walls.
That layer does not evaporate all at once. It releases odour molecules slowly over years, which is why a room seems odour-free with the windows open and smells again once it is closed.
Wiping and painting therefore only address the outermost layer, while ozone gas penetrates to the layers beneath and reacts with those molecules directly. That difference is what decides the outcome.
What ozone is, and why it is safe when used correctly
Ozone is three oxygen atoms bonded together, written O₃, while the oxygen we breathe is O₂. That third atom is unstable, so it readily detaches to react with other things.
That is the source of both its effectiveness and its precautions. The detaching atom oxidises the cell walls of bacteria, mould and viruses, and the molecules that cause odours, damaging their structure so they no longer function or no longer smell.
When the reaction is complete, what remains is ordinary O₂ oxygen. There is no chemical residue on surfaces and nothing to wipe down — unlike many spray-applied products.
The precaution is that while ozone levels are high, people and pets must not be in the area. That is why the standard procedure requires sealing the space, leaving during the treatment, and ventilating until the ozone smell is gone before returning.
Frequently asked questions
Does ozone really remove cigarette smell?
Yes, when done correctly with the exposure time matched to the severity of the odour, because ozone reacts directly with the odour molecules rather than masking them. In a unit smoked in continuously for years, more than one cycle may be needed, which we assess during the site survey.
Do we have to move the furniture out?
No. Ozone treatment works on a fully furnished unit, and in fact the furniture should be there — upholstery, curtains and built-in wardrobes are exactly where the smell accumulates, so treating the whole unit at once is more thorough.
How long does it take?
The treatment takes around 30 minutes per cycle on the automatic timer. The space is then ventilated until the ozone smell has gone, after which it returns to normal use. For a typical condo unit, it is finished within a single day.
Is it safe for people and pets?
Yes, when the procedure is followed. People and pets must not be in the area during treatment, and you wait until ventilation has cleared the ozone smell before returning. Afterwards there is no chemical residue, because ozone reverts to oxygen.
Will it damage furniture or fabrics?
No, when concentration and exposure time are properly controlled — which is what the team assesses from the materials in the room during the survey. That is why assessing the space first is always the initial step.
Will I still need to repaint?
In many cases, no. If the problem is odour alone, ozone treatment solves it without painting. If the walls are visibly yellowed enough to affect the unit's presentation, painting becomes a cosmetic decision rather than an odour one.
Does it work on other smells, such as damp or pets?
On all of them. The same principle applies to musty damp, food, sweat, pet, paint and chemical odours, so a unit with several smells mixed together is handled in a single treatment.
What does it cost, and is anything included?
The price depends on the size of the space and the severity of the problem. Send us the unit size and details for an assessment — and on bookings of 15,000 baht or more you also receive a free medical-grade disinfection spray service using CHEMGENE HLD4H.
One month of lost rent costs several times an ozone treatment
Manat lost over 100,000 baht on a single unit — 38,000 baht on cleaning and paint and 76,000 baht in rent over four months — before learning that the problem was not cleanliness but what was embedded in the materials, where a cloth cannot reach.
Ozone treatment takes around thirty minutes per cycle, requires no furniture removal and no repainting, leaves no residue, and costs a fraction of a single month's lost rent.
If you have a condo, a rental unit, an apartment or a house with an embedded smell that makes it unlettable, send us the size of the space and details of the problem, and we will tell you how many cycles it needs and how long it will take.
See the ozone disinfection and odour removal service — click here
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Call 065-556-6294 or add LINE @whd268
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