A 42-Room Apartment Building with Nine Rooms Nobody Would Rent: Five Months Empty and 187,500 Baht in Lost Rent
Last updated: 6 Sep 2026 | 7 Views |
Rooms that stayed empty not because nobody came, but because everybody left
A 42-Room Apartment Building with Nine Rooms Nobody Would Rent: Five Months Empty and 187,500 Baht in Lost Rent
Why repainting, servicing the air conditioners and replacing the curtains changed nothing, and why thirty minutes of ozone did
The tenant moved out months ago, but their smell did not. And it is costing you more than forty thousand baht a month. This is the story of a Lat Phrao landlord with nine rooms she could not fill.
Khun Wipha is 54 and owns a 42-room apartment building near Lat Phrao 101 that her father built 22 years ago. The location is good, the rent is 4,200 baht a room, and for two decades occupancy never dropped below 95 percent.
Then in early 2025 eleven tenants moved out together, because the factory they worked for relocated to Chonburi. Khun Wipha treated it as routine: clean the rooms, repaint, post the listings, refill.
Five months later, nine of those eleven rooms were still empty. Not for lack of interest — more than sixty people came to view them. Almost every one of them opened the door, stood there for about ten seconds, and asked the same question: could I see a different room, please?
The story
The ten seconds that decided everything
Khun Wipha says she noticed the pattern by the third week. Viewers would climb the stairs cheerfully, ask about the water and electricity rates, ask about parking, and then open the door of the room and change expression instantly.
Some were polite enough to walk in, look at the bathroom, open the wardrobe, and then say they would think about it. Others were more direct. One woman asked her outright whether someone had smoked in this room.
Khun Wipha answered honestly: yes, the previous tenant smoked, but he moved out four months ago and the whole room has been repainted. The woman smiled, thanked her, and never made contact again.
The part that hurt most was that Khun Wipha could barely smell it herself. She was in that building every day, walking past those rooms several times a day. Her nose had adapted to the point where it no longer registered. But anyone walking in from outside caught it in the first second.
What the old tenants left behind
Going room by room, she found it was not one smell. Rooms 204 and 207 were cigarette smoke embedded in the walls and ceiling. Room 311 was cooking oil — the previous tenant had prepared and fried food in the room every morning to sell to a curry shop.
Room 405 was animal odour. The building does not allow pets, but the tenant had kept two cats for nearly two years. Room 108 was damp and musty: a corner room the sun never reached, where the tenant dried laundry indoors year round.
What all of these had in common is that none of them lived on a surface you can wipe. Cigarette residue sits in the old paint layer and the gypsum ceiling. Oil vapour settles into the porosity of the walls and inside the air conditioning system. Cat odour lives in tile grout and under the skirting boards. Musty smell is literal mould growing in the air conditioner coil and behind the wardrobe.
She repainted every room, which helped for about ten days. After that the original smell seeped back through the new paint, because the source was still underneath it.
The number nobody wants to calculate
Nine rooms at 4,200 baht is 37,800 baht a month. Times five months is 189,000 baht. Subtracting the two rooms that were finally let in the fourth month leaves real losses of roughly 187,500 baht.
That does not include repainting nine rooms at 3,500 baht each — 31,500 baht. Or servicing nine air conditioners at 5,400 baht. Or replacing every curtain at 12,600 baht. Or the odour sprays and air purifiers she bought to experiment with, another ten thousand.
Total money lost to one problem — smell — was over 240,000 baht, in a building whose annual profit does not reach a million.
But Khun Wipha says the number is not what kept her awake. It was the feeling that the building her father built with his own hands was becoming a building people walked into and walked straight back out of.
The day her son found the answer
Her son, 29, works at a hotel in Sukhumvit. He told her that when a guest smokes in a non-smoking room, housekeeping calls in an ozone team before the room is sold again, and the room goes back on sale the same day.
Khun Wipha had never heard of ozone treatment. She assumed it was some kind of chemical spraying. Her son explained that it is not: it is a gas released into a sealed room, and the gas reaches everywhere air reaches, including inside the air conditioning and behind the furniture.
She booked a trial on two rooms first — 204, the worst of the cigarette rooms, and 405, the cat room, because those were the two where viewers left fastest.
The team arrived on a Wednesday afternoon and spent about thirty minutes per room following the machine's cycle, then ventilated. Khun Wipha walked into room 204 at five in the evening and stood in the middle of the floor for a full minute, because she genuinely could not tell whether she smelled nothing because her nose was used to it, or because there was nothing left to smell.
What it actually costs
An empty room loses money daily, not monthly
At 4,200 baht a month, a room earns 140 baht a day. Nine rooms is 1,260 baht every single day. Every day a room stays unlet, that money is gone permanently — there is no way to recover it later and nobody compensates you for it.
Viewers decide in ten seconds
Prospective tenants do not decide based on room size or price. They decide on the feeling when the door opens. Smell is the first thing the brain processes, and it happens before they have consciously seen anything at all.
Reputation damage spreads well beyond the viewers
People who look and leave do not stay quiet. They tell friends, they post in room-hunting groups, and some review the building's page. A building that once had a waiting list becomes a building people describe as smelling — which is far harder to recover than a single vacancy.
Mould and bacteria do not wait for a new tenant
A musty smell in a closed room is a signal that mould is actively growing. The longer a room sits empty with the air conditioning off and no ventilation, the further mould spreads from the coil into walls, ceilings and built-in furniture. What began as an odour becomes a real repair bill.
Why the usual fixes fail
Repainting over it
New paint masks odour for one or two weeks, because the paint smell is stronger. But the cigarette and cooking-oil molecules embedded in the original wall material and the ceiling board are all still there. As the paint smell fades, the original smell comes back exactly as it was.
Servicing the air conditioner
Cleaning the coil and filter genuinely helps with that part. It does not reach inside the duct work, the void above the ceiling, or the non-removable sections of the unit. More importantly, it does not touch the odour living in the walls, the floor and the skirting at all.
Odour neutralisers and air fresheners
Fragrance does not remove an odour molecule; it adds a new one on top. The result is a room that smells of cigarettes and synthetic flowers at the same time, which viewers immediately read as something being covered up — and that makes them more suspicious, not less.
Air purifiers
An air purifier filters particles from the air that passes through it. It cannot pull odour out of the material it is embedded in. Switch it off and the walls resume releasing odour into the air within hours.
Leaving the windows open to air it out
Ventilation dilutes airborne odour temporarily but does nothing to the source. In Bangkok it also brings in dust and humidity, which is fuel for the mould already growing in an unoccupied room.
The problem is not on the surface, it is in every cavity a hand cannot reach
Every method Khun Wipha tried shared one limitation: it only works where it physically touches the source. Brushes, cloths, chemicals and paint all operate on surfaces you can see and reach.
But the smell keeping those rooms empty was not there. It was in the porosity of the plaster, in the ceiling board, in the air conditioning duct, under the skirting, behind the built-in wardrobe, and in the bathroom grout — every place you would have to demolish something to reach.
Ozone solves this on an entirely different principle. Ozone is a gas. Released into a sealed room, it spreads everywhere air spreads, which is exactly where the odour is hiding. When an ozone molecule meets mould, bacteria or an odour compound, the third oxygen atom breaks away and oxidises it — destroying the cell wall of the organism and breaking the odour molecule into compounds that have no smell. Then the ozone itself decomposes back to ordinary oxygen, leaving no residue and adding no humidity.
10 reasons ozone treatment solves it
1. It reaches everywhere paint cannot cover
Ozone is a gas, so it penetrates wall porosity, ceiling board, the space behind built-in wardrobes, under skirting, inside air conditioning ducts and into bathroom grout — without dismantling a single thing.
2. It destroys the source rather than masking it
Ozone oxidises the odour molecules and the organisms producing them. Once the source is gone the smell does not return in ten days the way it does after repainting or spraying fragrance.
3. The Master Ozone Generator is certified by the Department of Medical Sciences
WHD uses the Master Ozone Generator, the only ozone brand in Thailand certified by the Department of Medical Sciences, Ministry of Public Health, and tested by Intertek UK.
4. 99.99% removal of embedded mould
Testing confirms 99.99% removal of deep-seated mould in air conditioning systems and furnishings, with virus and bacteria kill an order of magnitude beyond that. A room closed up for months is always a room with mould.
5. No chemical residue in a room someone will live in
Ozone decomposes back into oxygen. There is no film on the floor or walls, nothing for a new tenant to wipe off, and no chemical smell to explain away.
6. It adds no humidity
Scrubbing and steam add water to a room that is already closed and damp, which feeds mould directly. Ozone is a dry gas — it works without leaving moisture behind as fuel for the next cycle.
7. About thirty minutes per room
The automatic digital timer cycle runs roughly thirty minutes: two minutes to start, twelve to disperse, twelve to purify the air, twelve to rest. Then the room is ventilated and can be shown the same day.
8. Multiple rooms can be treated in sequence
For apartment buildings and dormitories the team works through a whole floor consecutively. The building does not close, other tenants are not disturbed, and nothing has to be moved out.
9. Every odour handled in one cycle
Cigarette, cooking oil, pets, damp, sweat and old paint are all addressed at once. You do not have to decide which smell to fix first.
10. Five-star hotels use exactly this method
The Ritz-Carlton, Fraser Suites, Andaz Hotels and Dusit International use ozone treatment on rooms they must sell to a paying guest the following night. The standard applied to your rental room is the same standard applied to theirs.
Before and after
Before
- Nine rooms unlet for five consecutive months, over 60 viewings and not one signature
- Approximately 187,500 baht of rent that should have been earned, gone
- More than 55,000 baht spent on repainting, air conditioner servicing, curtains and odour products with no result
- Viewers saying outright that the room smelled of cigarettes, then never contacting her again
- People beginning to mention the building in room-hunting groups as the one where rooms smell
- Occupancy falling from 95 percent to 78 percent for the first time in 20 years
After
- No detectable odour in any of the nine rooms, including the worst cigarette room
- All nine rooms let within three weeks of treatment
- About thirty minutes per room, all nine completed across two days
- The two-year-old musty smell in the corner room gone as well
- Occupancy back to 98 percent the following month
- A line in every listing stating that all rooms are ozone-disinfected before handover, which viewers ask about every week
How we get you started, in 3 steps
Survey and assessment
The team inspects each room, assesses the size, the type of odour and the likely accumulation points such as the air conditioner coil, the ceiling void and the space behind built-in furniture, then sets the treatment volume and cycle to suit that room.
Preparation and sealing
Any visible staining or mould is surface-disinfected first. Doors and windows are sealed, the air conditioning is set to recirculate so the duct work is treated too, and everyone leaves. Nobody is in the room during the cycle.
Ozone cycle, ventilation and check
The machine runs its automatic cycle of about thirty minutes. The room is then fully ventilated, surface moisture is checked, and it is ready to be shown or handed over the same day.
What a customer says
“At first I thought I would have to tear out the whole ceiling, because the contractor said the cigarette smell had gone all the way up into it. He quoted over twenty thousand baht per room. I tried ozone on two rooms first, and when I walked in that evening I stood in the middle of the floor for a long time because I did not believe it. In the end we did all nine rooms in two days and they were all rented within three weeks. Now I ozone-treat every room before handing it to a new tenant, as standard.”
Khun Wipha T. — owner of a 42-room apartment building, Lat Phrao
Why rental rooms accumulate odour more than almost any other space
A rental room is a small sealed volume occupied continuously. Cooking, drying laundry, smoking and sleeping all happen in the same air, for years, with almost no real ventilation because most tenants run the air conditioning and keep the windows shut.
The materials used in rental rooms are also highly absorbent: painted plaster walls, gypsum ceilings, plywood built-ins and fabric curtains. All of these are porous enough to hold odour molecules for years.
Combine that with Thailand's humidity, which sits at 70 to 80 percent for most of the year, and a closed room with organic residue becomes close to an ideal environment for mould and bacteria.
This is why a room left standing empty gets worse rather than better. With no air conditioning running and no ventilation, the organisms in a static system grow freely — the smell intensifies over the months instead of fading.
What every landlord should do the moment a tenant moves out
The lesson Khun Wipha took from this is that ozone treatment should not be something you do when there is a problem. It should be a standard step at every move-out, the way hotels handle any room with an odour issue.
The cost of treating one room is a small fraction of one month's rent, while one month of an unlettable room is a full month's rent lost with no possibility of recovery. The mathematics are not close.
The second benefit landlords overlook is marketing. A listing that states every room is ozone-disinfected and deodorised before handover is something almost no competitor in the same neighbourhood says — and it answers the question every tenant is worried about but too polite to ask.
The third is the health of the new tenant. An ozone-treated room is not merely odour free; it is free of mould in the air conditioning, free of dust mites in the corners and free of the bacteria the previous tenant left behind. For an allergic tenant, that is the difference between a room they can live in and a room they leave within three months.
Frequently asked questions
How long does one room take?
The automatic cycle is about thirty minutes, plus ventilation. A room can be shown or handed over the same day. For buildings with multiple rooms the team works through them consecutively.
Do I have to empty the room first?
No. Ozone is a gas that reaches into cupboards and behind furniture, so nothing needs to be removed. We do recommend leaving wardrobes and drawers open so the gas circulates fully.
Is it safe for tenants in neighbouring rooms?
Yes. The treated room is sealed during the cycle and nobody is inside it. After the cycle the room is fully ventilated before use. Ozone decomposes back into ordinary oxygen, so there is no residue to travel elsewhere.
Can it really remove cigarette smell that has been there for years?
Yes, because ozone does not work on the surface — it is a gas that reaches the wall and ceiling porosity where the residue actually is. Very deeply embedded cases may need more than one cycle, which the team will assess at the survey.
Will I still need to repaint afterwards?
No. If you have already painted, that is not wasted, but if you have not, treat first and then decide. Many rooms need no repainting at all once the smell is gone, saving several thousand baht per room.
Does ozone damage paint or furniture?
No. The cycle is controlled for concentration and duration by the certified machine's digital timer. It does not strip paint, does not fade curtains and leaves no moisture to swell timber.
What certifications does the equipment hold?
WHD uses the Master Ozone Generator, the only ozone brand in Thailand certified by the Department of Medical Sciences, Ministry of Public Health, and tested by Intertek UK.
Is there anything included for multi-room bookings?
For bookings of 15,000 baht and above, WHD includes free hospital-grade CHEMGENE HLD4H spray disinfection — well suited to apartment buildings treating several rooms at once.
Five months empty cost her nearly 200,000 baht. Ozone takes half an hour per room.
If viewers are leaving your rooms unusually fast, the problem may not be the price or the location. It may be what they smell in the first ten seconds — a smell you can no longer detect because you have lived with it too long.
Ozone treatment reaches the odour where painting and cleaning cannot, destroys the source instead of covering it, leaves no residue in a room someone will live in, and finishes in about thirty minutes per room using equipment certified by the Department of Medical Sciences.
For bookings of 15,000 baht or more, WHD includes free hospital-grade CHEMGENE HLD4H spray disinfection.
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