A typical scenario (an illustrative example case, not an interview with any resident)

May works in an office near Ratchadaphisek Road and rents a ground-floor unit in a mid-sized condominium off Pracha Uthit. She chose the ground floor for simple reasons: lower rent, no waiting for the lift, and a small balcony that opens onto the building's garden.

On the evening the rain would not stop, she was stuck in traffic for hours. When she finally opened her door, water had crept in along the balcony door frame. The laminate floor was wet in a long strip, the doormat was soaked, and the legs of her fabric sofa and bed had wicked up a brown tide line. Downstairs, the housekeeper was squeegeeing water off the marble lobby floor, and in the car park, water sat in the corners while the floor drains gave off a sewer smell.

Three days later everything looked dry, but the smell in the unit was getting worse, not better. It was a stale, damp odour mixed with a drain smell that clung to the curtains and to the clothes in her wardrobe. Every time she switched on the air conditioner, the cold air seemed to push the smell into every corner. Small black dots appeared along the wall next to the balcony. May started waking up with a blocked nose, and her flatmate, who has allergies, sneezed every time she walked in.

What May experienced is common. A city condominium does not need to be under a metre of water to have a problem. A few centimetres of water entering a ground-floor unit, or standing for hours in a car park or plant room, is enough to leave behind germs and the moisture that mold needs to grow.

Where Huai Khwang Flooded in 2026, According to News Reports

The points below come from news reports and official announcements published in late September 2026. Water levels were measured at the time of each report and change constantly.

• Vibhavadi Rangsit Road, Huai Khwang section: on the morning of 25 September 2026 the road was flooded 10 to 15 cm deep over roughly 600 metres, while Phetchaburi Road had about 5 to 10 cm of water (Nation TV).
• New Phetchaburi Road near Singha Complex: on 26 September 2026 the water level was measured at 14.7 cm; the waterlogging began at about 15:10 on 25 September (Thai PBS).
• Pracha Uthit Road, opposite the Huai Khwang District Office: listed as one of Bangkok's waterlogged points at 18:30 on 25 September 2026 (Naewna).
• Official assistance zone: the Department of Disaster Prevention and Mitigation (DDPM) declared Bang Kapi, Samsen Nok and Huai Khwang subdistricts as flood assistance zones.

Across Bangkok, rainfall on 25 and 26 September 2026 exceeded 300 mm in about 48 hours. On 26 September all 50 districts were declared disaster areas. Waterlogged points rose from 43 on the evening of 25 September to 135 on 27 September, and a DDPM report on 6 October 2026 put the number of affected Bangkok households at 329,000 (Thai PBS, Naewna, Bangkok Biz News).

Huai Khwang is one of Bangkok's densest condominium districts, with towers and apartment blocks along Ratchadaphisek, Pracha Uthit and New Phetchaburi. These buildings did not go under water, but their lowest points always take the water first: car park ramps, pump rooms, bin rooms, ground-floor units with garden-level balconies and lobbies whose doors open straight onto the street.

Condo Ozone Disinfection After Floods in Huai Khwang: What City Floodwater Leaves in Your Unit

Floodwater on Bangkok's roads is not clean rainwater. When heavy rain overwhelms the drains, the water on the street mixes with drain water, overflow from sewer manholes, rubbish, food waste, animal droppings and road grime. That mixture can reach lobbies, car parks and ground-floor units through doors, ramps and floor drains that back up. What it brings in and leaves behind falls into several groups.

Bacteria from sewage

Bacteria carried by sewage-contaminated water, such as E. coli and Salmonella, cause diarrhoea, stomach cramps, nausea and vomiting. They stay on floors, skirting boards, table legs, rugs and anything the water touched. A hand that touches a contaminated surface and then food, or a toddler crawling on the floor, can pick them up. Standing urban floodwater also carries a risk of leptospirosis, spread through water or soil contaminated with rat urine, especially for people who waded home or went down to the car park to move belongings.

Viruses on surfaces and in shared spaces

Norovirus and rotavirus, which cause diarrhoea and vomiting, can travel with sewage and survive on surfaces. Respiratory viruses such as influenza and RSV spread more easily when people are crowded in closed, humid rooms and worn down from days of cleaning. In a condominium, the lift buttons, handrails and lobby doors are touched by many hands every day.

Mold that grows quietly after the water recedes

Mold arrives later than other germs but stays the longest. Its spores are always in the air, and once they find a damp surface with something organic to feed on, such as gypsum board, wallpaper, laminate, plywood, curtains or sofa cushions, they can start growing within 24 to 48 hours. That is why the WHO and the US CDC advise cleaning and drying as soon as possible after a flood. Mold triggers allergies, sneezing, a blocked nose and itchy eyes, and can make asthma worse.

Musty odours, drain smells and smelly air conditioners

The musty smell comes from volatile compounds released by mold and bacteria as they break down wet materials. The drain smell comes from sewer gas pushed up through the plumbing. Both soak into fabric, foam, wood and porous walls. Condos have one more hiding place that people forget: the air conditioner. When humidity is high and mold spores are in the air, the cooling coil, drain tray and blower wheel collect damp dust and mold, and every time the unit runs, it spreads the smell around the room.

Who is most at risk

Older people, young children who put their hands in their mouths, pregnant women, people with chronic conditions such as diabetes, kidney or lung disease, and anyone with allergies or asthma need extra care. So do building staff working in car parks and plant rooms. Anyone who develops a fever, muscle pain (especially in the calves), red eyes, persistent diarrhoea or difficulty breathing after contact with floodwater should see a doctor and mention the flood exposure. Do not wait for symptoms to get worse.

What Owners, Tenants and Juristic Persons in Huai Khwang Face

Health. People living with musty air and mold usually start with small symptoms: a blocked nose on waking, a scratchy throat, an itchy rash. Over time these can disturb sleep.

Money. If mold is allowed to spread into gypsum walls, built-in wardrobes and under laminate flooring, repairs cost far more than dealing with it early. Some furniture holds a smell so stubbornly that it has to be thrown out. For landlords, a smelly unit can lead tenants to move out or ask for lower rent.

Time. Scrubbing, spraying and airing things out again and again while the smell keeps coming back eats up weekend after weekend, and city workers rarely have time to spare.

The building's reputation. For a condominium's juristic person, a sewer smell in the lobby or a musty car park is the first thing residents, visitors and prospective buyers or tenants notice. Posts in residents' online groups travel fast and affect rents and resale prices.

Why the Usual Fixes in a Condo Do Not Make the Smell and Germs Go Away

Wiping floors with disinfectant only. Disinfectants and bleach work on smooth surfaces you can reach, but not in the joints of laminate flooring, behind built-in wardrobes, under beds, inside curtain fabric or in the air. Strong bleach in a closed condo unit also gives off harsh fumes that irritate the airways, and it must never be mixed with toilet cleaners or ammonia, because that releases dangerous gases.

Running the air conditioner to dry the room. Air conditioning removes some moisture, but if spores and odours are already in the room, it circulates them, and mold may settle in the cooling coil so the unit starts to smell on its own even after the room is dry.

Painting over mold. Fresh paint on a wall that is still damp or has mold inside looks clean for a few weeks. Then the black spots push through again and you pay twice.

Opening the window and running a fan. Many condo units have windows on one side only, so there is no cross-breeze. Fans do help surfaces dry faster, and you should use them, but they do not kill germs or break down odour molecules trapped in materials.

Treating only your own unit. If your unit is clean but the corridor, lobby or car park still smells, germs and odour come back in on shoes, suitcase wheels and the air through the door. Effective recovery means talking to the juristic person and planning the common areas and the units together.

How Condo Ozone Disinfection After Floods in Huai Khwang Works with WHD

Ozone (O3) is oxygen with one extra atom and a strong oxidising effect. Released into a sealed room, it spreads through the whole space, including corners, the underside of furniture, the inside of fabrics and gaps that a cloth cannot reach. Ozone breaks down the cell structures of viruses, bacteria and mold and breaks apart the molecules that cause odours, rather than covering them up. Afterwards it reverts to ordinary oxygen (O2), so it leaves no chemical residue on surfaces.

According to test results the company has had certified by Thailand's Department of Medical Sciences and Intertek (UK), the ozone system used by World Health Disinfection (WHD) eliminates viruses, bacteria and mold at 99.99%. You can see the documents on the certification page.

The service process for units and common areas

1. Talk it through by phone or LINE. Tell the team the condo name, floor, unit size, where the water came in and what the smell is like, and send photos for an initial assessment. For common areas, the juristic person coordinates.
2. Book a date and arrange building access. Appointments are made in advance according to the queue, with no same-day promise.
3. Prepare the space. Make sure mud has been removed, soaked items thrown out and the unit dried. Everyone, including pets and plants, leaves the space. Windows and doors are closed.
4. Treat zone by zone. The machine runs one zone at a time, for example bedroom, living room and bathroom, or sections of the car park and lobby. A typical cycle is about 30 minutes per zone, depending on size and smell.
5. Contact time and rest. The ozone works for the set time, then the space rests while ozone reverts to oxygen.
6. Ventilate before re-entry. Open up and go back in only when the technician says it is safe.

It is worth stressing again: ozone treatment is done in an empty, closed space with no people, pets or plants, because high concentrations irritate the airways. In a condominium this means planning with the juristic person to close common areas temporarily and telling residents in advance. Ozone is a step after mud removal, cleaning and drying. It does not replace removing soaked materials, fixing leaks or backflowing drains, or seeing a doctor when someone is ill.

The service suits individual units, monthly rentals, apartment blocks, lobbies, gyms, bin rooms and car parks. Read the full details on the residential ozone disinfection service page, or see how ozone handles odours on the ozone cleaning service page.

10 Reasons to Choose Condo Ozone Disinfection After Floods in Huai Khwang

1. It reaches where a cloth cannot. As a gas, ozone gets under beds, behind wardrobes, into floor joints and into curtain fabric.
2. It tackles several kinds of germs in one treatment. Bacteria, viruses and mold, at 99.99% according to the company's certified test results. See the ozone service page.
3. It breaks down odour at the source instead of layering a perfume over musty and drain smells.
4. No chemical residue. Ozone reverts to oxygen, which matters when young children or older relatives move back in.
5. It helps with smelly air-conditioned rooms. Combined with cleaning an air conditioner that sat in damp air, it stops the airflow from bringing the musty smell back.
6. It is quick. About 30 minutes per zone, so it can be done during a working day.
7. It suits building common areas. Lobbies, car parks, bin rooms and gyms can be treated in zones on the juristic person's schedule. More on the building ozone service.
8. It protects the value of the unit. A unit without a smell is easier to rent out or sell.
9. It works well with cleaning. After washing and drying, ozone finishes the job where liquids cannot go.
10. The team is based in Bangkok. WHD's office is in Bang Khae, and service in Huai Khwang can be booked in advance by phone or LINE, with the date confirmed according to the queue.

Example Case: A Juristic Person on Pracha Uthit Road

(An illustrative example case to explain the process, not a review from any customer)

Ton manages the juristic person of an eight-storey condominium off Pracha Uthit. After the late-September downpour, water ran down the ramp into the ground-level car park and into two or three ground-floor units next to the garden. The car park floor drains backed up. When the water receded, a thin film of mud covered the floor and a sewer smell drifted up into the lobby.

His plan went like this. On day one, housekeepers and a contractor hosed the mud out of the car park, scrubbed the drains, checked the manhole covers and ran industrial fans to dry everything. On day two, he asked ground-floor owners to throw out soaked rugs and mattresses and remove swollen skirting boards. Only then did he book the ozone team. The car park was closed half at a time while residents parked out front, the lobby was treated late at night when no one was using it, and the ground-floor units were done on days when the owners were out.

What Ton says he learned: ozone applied while floors are still wet does not perform as well, because the moisture lets mold grow back. Following the order of wash, discard, dry and then treat is what stops the smell from returning.

Condo Recovery Checklist: Before and After Ozone

Before ozone

• Photograph the damage in the unit and common areas for insurance claims or the juristic person.
• Switch off the unit's breaker before cleaning. If water reached the sockets, have an electrician check before using power.
• Wear rubber gloves, boots and a mask while cleaning, and wash your hands after every session.
• Throw out rugs, mattresses, cushions and absorbent items that stayed soaked too long to clean.
• Remove swollen skirting, lower gypsum panels or laminate so the cavity can dry.
• Wash floors and walls with clean water and detergent, then dry with fans or a dehumidifier.
• Clean the air conditioner, drain tray and filters if the unit sat in damp air for days.
• Pour water into bathroom and balcony floor drains so the traps hold water and block sewer gas.
• Remove people, pets, plants and fresh food before the appointment.

After ozone

• Wait for the technician's go-ahead, then ventilate as advised.
• Keep humidity under control with dry mode or a dehumidifier during continued rain.
• Watch the walls for new dark spots over the next two to three weeks. If they appear, moisture is still coming in and the source must be fixed.
• If water still seeps through the balcony or drains still back up, report it to the juristic person or a plumber before the next storm.
• If anyone has a fever, diarrhoea, calf pain or breathing problems, see a doctor.

More flood safety advice: CDC Floods and the Department of Disease Control.

FAQ: Condo Ozone Disinfection After Floods in Huai Khwang

Q: My unit is on a high floor and stayed dry, but it smells musty. Should I use ozone?
A: High-floor units can smell because of humidity during days of rain, laundry that never dried, or a moldy air conditioner. Find the cause first: clean the AC and check for window leaks. If the smell remains, ozone can deal with odour and germs in the air.

Q: How long do I need to stay out?
A: Each zone typically takes about 30 minutes, plus rest and ventilation time. The technician will tell you the right timing for your unit and when it is safe to go back in.

Q: Can I treat just my unit? Do I need permission from the juristic person?
A: Yes, a single unit can be treated, but you should inform the juristic person about the team's access and equipment according to the building's rules.

Q: Will ozone stop my air conditioner from smelling?
A: Ozone reduces odour and germs in the room, but if slime and mold have built up in the coil and drain tray, the AC should be cleaned as well for a better and longer-lasting result.

Q: The walls are still damp. Can I treat now?
A: Wait until they are dry. If materials are still wet, mold can grow back after treatment. Always clean and dry first.

Q: How much does it cost?
A: It depends on the area, the number of zones and the condition of the space. The team assesses and quotes by phone at 065-556-6294 or LINE @whd268. Jobs of 15,000 baht or more come with a free medical-grade disinfectant spray.

Q: I got diarrhoea after cleaning up. What should I do?
A: Drink oral rehydration solution and see a doctor, especially with a fever, if it does not improve, or if the person is a young child or older adult. Ozone treats the space, not illness.

Still smelling damp in your Huai Khwang condo after the flood? Talk to WHD about an ozone plan.

Phone 065-556-6294 | LINE @whd268 | worldhealthdisinfection@gmail.com
Office in Bang Khae, Bangkok 10160. Appointments by advance booking.

Related Services and References

• Residential and building ozone disinfection
• Disinfection service for homes and buildings
• Contact us

References

• Nation TV: waterlogging on Vibhavadi Rangsit and Phetchaburi, 25 Sep 2026
• Thai PBS: Bangkok road water levels, 26 Sep 2026
• Naewna: Bangkok waterlogged points, 25 Sep 2026
• Thai PBS: rainfall by district, 25 to 26 Sep 2026
• Bangkok Biz News: DDPM flood situation, 6 Oct 2026
• CDC: Floods and cleanup safety
• WHO Fact sheets

Note: water levels and figures in this article are as reported on the dates stated and change daily.