A Story from the Field: The 27th-Floor Unit the Water Never Touched

Prae is a 32-year-old marketing executive who lives in a one-bedroom unit on the 27th floor of a condominium near Phetchaburi Road in Ratchathewi, Bangkok. Like many people who choose high-rise living, she always assumed that being up so high meant one thing for certain: whatever happened during the rainy season, floodwater would never be her problem. And in one sense she was right. During the 2026 floods, not a single drop of water reached her unit.

What she had not considered was everything that sits below her. When the streets around the building flooded, water poured down the ramp into the underground car park and reached the main electrical room and the water pump room. For safety, the juristic person managing the building had no choice but to cut power to the entire tower. The lifts stopped. Tap water could no longer be pumped to the upper floors. The corridor ventilation fans and the central air conditioning serving the lobby and common areas went silent. Prae walked down more than twenty flights of stairs with a single bag and went to stay with her parents in Nonthaburi for almost two weeks.

Before she left, she did what most of us would do. She closed every window in case rain blew in. She did not think about the load of laundry still sitting damp in the washing machine, the towels draped in the bathroom, the fridge full of fresh food and milk, or the water still sitting in the drain tray of her split air conditioner. All of it was sealed inside a unit with no electricity, no air conditioning and no air movement, in the hot, heavy humidity of a Bangkok September and October.

On the day power returned and the lifts came back, Prae opened her front door and stepped straight back out again. A thick, musty smell mixed with the sour stench of spoiled food from the fridge hit her at once. Her leather sofa was covered in pale grey spots of mold. The bottom hems of her curtains had black specks. The clothes in her wooden wardrobe smelled like laundry that had never dried. When she switched on the air conditioner, hoping to dry the room out, the air that came out smelled even worse than the room. Her mother, who has dust and mold allergies, came to help her sort things out and lasted barely half an hour before she began sneezing and complaining that her nose was blocked.

"Water never came into my room. How can it be like this?" was the first thing Prae asked our team. The shortest honest answer is this: a fully sealed room with no power, no air conditioning and several sources of moisture inside it is exactly the environment mold loves in a tropical climate. You do not need a flood inside your unit to end up with a flood-season mold problem.

Why a Unit That Never Flooded Can Grow Mold So Quickly

Most people think of post-flood mold as something that only happens to ground-floor homes that sat in water. In reality, mold needs only three things to thrive: high humidity, warmth, and something to feed on, such as dust, fabric, leather, wood, paper or food residue. A condo unit left sealed during a long power outage has all three in abundance. Here is what typically happens.

• The air conditioner was your main dehumidifier. In everyday life, a split air conditioner constantly pulls moisture out of the air as it cools. Many residents never realise how much water it removes until it stops. After several days without power, indoor humidity climbs until it matches the very damp outdoor air of the flood season.
• Moisture sources inside the unit. Wet laundry in the machine, damp towels and bath mats, water in the air conditioner drain tray, melting ice from the freezer and even the water in toilet bowls and sink traps all release vapour into a room that has no way to vent it.
• Condos are sealed more tightly than houses. Modern condominiums are designed to be airtight to save energy. Once the bathroom exhaust fan and the corridor ventilation stop, the air inside a unit is barely exchanged at all. There are no gaps under the roof, no open eaves and often only one wall with windows.
• Corridors and shafts become stale too. When the corridor fans and the central air in common areas stop, damp air and odours from the flooded lower levels can rise through stairwells and service shafts and seep into units through the gap under the front door.
• A fridge without power. Spoiled food is not just a smell. It becomes a breeding ground for bacteria and mold, and the odour soaks into the rubber door seals, plastic liners and the drip tray underneath.

In short, a high-floor unit does not suffer the same damage as a flooded house. Its problem is accumulated humidity and odour absorbed into soft materials, and that calls for a slightly different approach.

The Impact Goes Far Beyond an Unpleasant Smell

Health. Airborne mold spores are a major trigger for allergy symptoms: sneezing, a blocked or runny nose, itchy eyes and a lingering cough. They can also make asthma worse. People who spend time in a stale, musty room often experience headaches, a feeling of not being able to breathe freely, or poor sleep without realising why. Spoiled food in a fridge carries a risk of stomach upsets and diarrhoea if containers and shelves are handled without proper cleaning. And residents who need to go down to the car park or the lower levels where floodwater stood should be careful about leptospirosis, a bacterial infection that can be picked up from contaminated water and mud, especially through cuts on the feet. Wear boots, and if you develop a fever after contact with floodwater, see a doctor and mention the exposure.

Belongings. Leather sofas, fabric cushions, mattresses, curtains, clothes in wardrobes, leather bags, shoes and books are the items most likely to grow mold in a closed room. The longer they are left, the more likely the stains become permanent. Some of them may need to be thrown away even though they never touched a drop of water.

Time and work. Most condo residents in central Bangkok work in the city. Coming back to a unit you cannot live in means taking leave, staying elsewhere for longer, or putting up with the smell night after night, often carrying it on your clothes to the office.

Property value. For units that are rented out, a musty smell and mold stains are the very first things a tenant or buyer notices. A unit with a history of mold and odour can be harder to let and harder to negotiate on.

Before You Start: What to Check with the Juristic Person

Working in a condo is different from working in a detached house, because your unit is connected to shared building systems for electricity, water and air. Before you begin restoring your room, it is worth asking the building's juristic person about the following.

• Has the building's electrical system been inspected by the building engineer or a qualified electrician, and is there any advice about switching appliances back on inside the units?
• Has the water supply been restored according to the building's procedures, for example after cleaning the storage tanks? It is sensible to run the taps for a while before using the water.
• Are the corridor ventilation fans and the central air conditioning in common areas fully working again? If not, you may need to plan for extra ventilation inside your unit.
• What are the building's rules for contractors and service teams entering a unit, such as advance notice, booking the service lift and permitted working hours?
• If you plan an ozone treatment inside your unit, let the juristic person know in advance. They can help reassure neighbours who ask questions, and it allows the service team to seal the gap under the corridor door properly.

Electrical safety inside your unit is a job for an electrician, not something a disinfection team should decide for you. If any socket or appliance smells of burning or behaves strangely, stop using it and call an electrician first.

Why the Usual Quick Fixes Do Not Solve the Problem

• Running the air conditioner all day to dry the room. If the cooling coil and drain tray of the air conditioner already have mold growing on them, running the unit simply blows spores and odour around the whole room. It should be cleaned by an air conditioning technician first.
• Spraying air freshener. A fragrance only masks the musty smell for a short time. It does nothing about the source, and the combination of perfume and mildew often makes the room smell strange and even more unpleasant.
• Wiping mold with bleach alone. Bleach can lighten stains on hard, smooth surfaces, but it is not suitable for leather, fabric or wood. Its sharp fumes are unpleasant in a closed room, and it does nothing about spores floating in the air or hiding behind furniture.
• Opening the balcony door and calling it done. High-floor units often get strong wind but open on only one side, so air does not circulate evenly. The inside of the wardrobe, the space behind the sofa and under the bed stay just as stale as before.
• Cleaning only the inside of the fridge. Odour from spoiled food tends to soak into the rubber door seals and the drip tray at the bottom. If those parts are not cleaned, the smell keeps coming back.
• Repainting or buying new furniture straight away. If the humidity and the spores in the room are not dealt with first, new items can grow mold again within a few weeks.

The Right Order: Remove the Moisture Sources First, Then Disinfect

1. Protect yourself before going in. Wear a mask that filters fine particles well and rubber gloves, and leave the front door open for a while before you start working. People with allergies or asthma, young children and older relatives should not be the ones sorting things out on the first day.
2. Deal with the fridge. Throw out all spoiled food in thick, tightly sealed bags and dispose of them where the juristic person tells you to. Then wash the shelves, the door seals and the drip tray underneath.
3. Remove wet and musty textiles. Laundry left in the washing machine, towels and bath mats should be rewashed or thrown away. Run the washing machine's drum-cleaning programme.
4. Have the air conditioner cleaned. An air conditioning technician should clean the cooling coil, the blower wheel and the drain tray, and check that the drain pipe is not blocked. This step alone removes one of the biggest sources of musty odour.
5. Sort out moldy items. Heavily molded items such as a mattress with a strong smell, pillows or cardboard boxes may need to go. Valuable leather goods and special items may need a professional cleaner.
6. Disinfection fogging of surfaces. A fine-mist fogging system reaches every corner to deal with germs on surfaces.
7. Ozone treatment. In a room that can be closed, ozone deals with spores and breaks down odour molecules trapped in fabrics and materials.
8. Keep ventilating and controlling humidity. Run the cleaned air conditioner or a dehumidifier to keep indoor humidity at a comfortable level.

The Solution: Disinfection Fogging and Ozone Treatment by World Health Disinfection

The World Health Disinfection (WHD) team restores condo units after floods and long power outages using two core services that work together.

Disinfection fogging service. We use CHEMGENE HLD4H disinfectant with ULV fogging equipment that turns the solution into an extremely fine mist. The mist spreads into corners, behind the sofa, inside open wardrobes and onto surfaces that are hard to reach by hand, which makes it well suited to dealing with bacteria and mold on surfaces throughout the unit.

Ozone treatment service. We run an ozone generator in a closed room. Ozone is a gas that spreads through the entire space, so it reaches into curtain fabric, upholstery, clothes in wardrobes and gaps that liquid mist cannot. It helps deal with airborne mold spores and breaks down the molecules responsible for musty smells, the stench of spoiled food and odours trapped in soft materials.

Used together in the right order, the two methods give the room both surface disinfection and odour removal from the air and materials. That combination is exactly what do-it-yourself cleaning usually misses.

How the WHD Team Works in a Condo Unit

1. Enquiry and assessment. We talk through the details by phone or LINE, ask for photos of the unit and the areas with mold or odour, estimate the size of the job and the time needed, and book a date that fits the building's rules.
2. Preparation advice. We recommend dealing with the fridge, wet textiles and air conditioner cleaning before treatment day. If some of these tasks are still pending, we advise on the best sequence.
3. Protecting sensitive items. Expensive electronics, sensitive equipment, artworks and certain collectibles are covered or moved out of the room. All indoor plants must be removed.
4. Fogging with CHEMGENE HLD4H. Fine mist is applied throughout the living area, bedroom, bathroom, balcony, open wardrobes and the entrance area.
5. Controlled-dose ozone treatment. Windows are closed, the gap under the corridor door is sealed, a warning sign is placed on the door, and the generator runs for a duration matched to the room size and odour level. No people or pets may be inside during this stage.
6. Ventilation. When the treatment time is complete, the team opens windows and balcony doors to clear the ozone until the room is ready for re-entry.
7. Re-check and aftercare advice. We check the smell and the areas that previously had mold, explain how to manage humidity during the first week, and arrange a follow-up check if needed.

Ozone Safety in a Condominium

• No people, pets or plants may be inside the unit during ozone treatment. If you have a cat or dog, arrange for it to stay somewhere else on the day.
• The room must be fully ventilated before anyone goes back in. The team will tell you when it is ready.
• We use a controlled dose, because very high concentrations of ozone over long periods can age rubber, some plastics and certain fabrics more quickly. Sensitive electronics and artworks are covered or removed.
• The gap under the corridor door is sealed so that ozone does not leak into the common corridor or neighbouring units.
• Always inform the juristic person in advance so the building can coordinate smoothly.

10 Reasons a Condo Unit Needs Proper Treatment After a Long Blackout

1. A sealed room without air conditioning for several days accumulates enough humidity for mold to grow, even when water never entered the unit.
2. Airborne mold spores trigger allergies and asthma, and ozone treatment helps deal with spores floating in the room.
3. Musty and spoiled-food odours soak into curtains, upholstery and clothing, and wiping alone cannot remove them.
4. Fine-mist disinfection fogging reaches places hands cannot, such as behind furniture and inside cabinets.
5. CHEMGENE HLD4H is used for surface disinfection without relying on bleach and its harsh fumes in a closed room.
6. It helps you keep belongings that are still usable instead of throwing them away just because they smell.
7. It saves time for busy city workers, so you do not have to put up with the smell or stay elsewhere longer than necessary.
8. Rental units are ready for tenants sooner, reducing the risk of losing a tenant or a sale.
9. Our team is used to working within condominium rules, booking service lifts and coordinating with juristic persons.
10. You get practical aftercare advice, including information on residential ozone disinfection, so the mold does not come back.

Before and After

Customer Voice

"At first I thought opening the windows for a few days would fix it, but the longer I stayed, the more I noticed the smell on my clothes at work. The team told me to get the air conditioner cleaned and empty the fridge first, then they did the fogging and the ozone. When I walked back in, it felt like I had my old room back. My mum can sit in the living room for hours now without sneezing." Prae, condo resident in Ratchathewi (a representative scenario from our field work)

Keeping Your Unit Dry for the Long Term

• For the first two weeks, run the air conditioner or a dehumidifier regularly and keep an eye on the corners where mold appeared before.
• Open wardrobe doors from time to time to let air circulate, and avoid packing clothes too tightly.
• Avoid drying laundry inside a closed room. If you must dry clothes indoors, run a dehumidifier at the same time.
• If you will be away for a long period in the future, do not leave wet laundry behind, empty the fridge if a power cut is likely, and empty the air conditioner drain tray if you can.
• Have your air conditioner serviced on schedule and dust the room regularly. If someone in the household is allergic to dust mites, consider our dust mite removal service as well.
• Ask the juristic person whether the building plans any improvements to protect the electrical room from future floods. Knowing the plan helps you prepare your unit before the next rainy season.

Frequently Asked Questions (FAQ)

Q: Water never entered my unit. Do I really need disinfection fogging?
A: If mold has appeared or there is a spoiled-food smell, fogging treats surfaces much more thoroughly than wiping by hand. If the unit only has a mild musty smell, the focus may be on ozone treatment and humidity control. Our team will assess the room first and recommend what is actually needed.

Q: Should the air conditioner be cleaned before the ozone treatment?
A: Yes, we recommend it. A moldy coil and drain tray are a source of odour that returns every time you switch on the air conditioner. Cleaning should be done by an air conditioning technician.

Q: Will the ozone treatment affect the units next door?
A: The team seals the gap under the corridor door, closes the windows and uses a controlled dose. We also recommend informing the juristic person in advance so the work runs smoothly with neighbours.

Q: How long do I need to stay out of the unit?
A: It depends on the size of the unit and how strong the odour is. As a rough guide, set aside around half a day including the ventilation period. The team will give you a clear time once the room has been assessed.

Q: Can my moldy leather sofa be saved?
A: If the mold is only on the surface, it can often be cleaned, but you should use products made for leather or send it to a leather care specialist. Fogging and ozone help with germs and odour in the room, but they do not repair stains or colour damage on leather.

Q: Do you serve buildings outside Ratchathewi?
A: Yes. We serve condos, houses, shophouses and offices across Bangkok and the surrounding provinces. Contact us by phone or LINE to check availability.

Let Your Ratchathewi Condo Breathe Again

Talk to the World Health Disinfection team about ozone treatment for musty odours and disinfection fogging after a long power outage. We are available every day.

Book Ozone Treatment, Click Here

View Disinfection Service, Click Here

Call 065-556-6294 · LINE @whd268 · worldhealthdisinfection@gmail.com

Related Links

• Residential ozone disinfection
• Ozone treatment for odours and chemical residue
• Master Ozone Generator
• All articles
• External source: WHO: Floods and health and Department of Health, Thailand