A typical scenario (an illustrative situation based on common experiences, not a review from any specific customer)

A dozen questions saved in a phone note

Mint lives in a two-storey townhouse in Bueng Kum with her husband, their eight-month-old daughter, her grandmother who has asthma, and a cat. During the heavy rain of late September 2026, water rose to about mid-shin on the ground floor. The family carried some belongings upstairs, but the fabric sofa, the wooden cupboard under the stairs and the living room rug sat in water for two full days.

Once the water went down, everyone pitched in to shovel out the mud, wash the floors and throw the rug away. Three days later the house looked far cleaner, yet every time they opened the front door, a damp, musty smell greeted them. Small black spots began to appear on the wall under the stairs, and Grandma started coughing more at night. A neighbour suggested ozone treatment. Mint spent the night reading online, and the more she read, the more questions she had. Is ozone dangerous? How long does the baby need to be out? Where should the cat go? Must the house be fully cleaned first? Will the mold really stay away? Should the fridge be emptied? Will the TV be damaged?

Mint saved more than ten questions in a phone note before calling for advice. This article gathers the same questions many Bangkok families have asked after this flood, with straight answers, including what ozone can and cannot do.

The late-September 2026 Bangkok floods in brief

According to news reports, between 24 and 27 September 2026 Bangkok received roughly 300 mm of continuous heavy rain in about 48 hours. On 26 September 2026 the Bangkok Metropolitan Administration declared all 50 districts a disaster zone. Eastern Bangkok was hit hardest, with Khlong Chan and Bueng Kum mentioned in coverage. Governor Chadchart Sittipunt said the canals were full and drainage would take around two to three days after the rain stopped.

Reports noted three deaths, a loss shared by the whole city. As of 30 September, some roads such as Si Burapha and Lat Phrao still had 20 to 40 cm of standing water. Thai media compared the event with the 2011 floods, and one business report cited a Chamber of Commerce estimate of around 12,300 million baht in damage.

As the city moves into recovery, many families are looking for ways to deal with germs and mold at home. Ozone treatment is one of the most discussed options, and also the one that raises the most safety questions.

Understand the problem first: what hides in a home after a flood

Before answering questions about ozone, it helps to understand what a flooded home is facing. Urban floodwater is not clean rainwater. It mixes with drain water, sewage, rubbish and animal urine. The World Health Organization, the US CDC and Thailand's Department of Disease Control all warn that after floods people should watch for gastrointestinal illness such as diarrhoea, skin conditions, wound infections and leptospirosis.

The problem that follows is moisture. Absorbent materials such as fabric sofas, mattresses, rugs, wooden cabinets, gypsum walls and wallpaper hold water for a long time. Health agencies advise cleaning and drying within 24 to 48 hours to limit mold. When that is not possible, mold begins to grow and release spores into the air, causing musty smells and triggering allergies, asthma, congestion, coughing or eye irritation.

People who need extra care include babies and young children, older adults, pregnant women, people with chronic illness or lung disease, and anyone with weakened immunity. If anyone in the household has a fever, muscle pain (especially in the calves after wading), diarrhoea or difficulty breathing, they must see a doctor before anything else. Restoring the house comes second; people's health comes first.

What families commonly face after a flood

• Health: coughing, sneezing, congestion, itchy rashes and poor sleep due to bad indoor air, especially for young children and older adults.
• Money: replacing furniture and repairing walls, with costs multiplying if mold is left to spread.
• Time: days off work to clean, and repeat cleaning because the smell will not go away.
• Peace of mind: exhaustion and worry about whether the home is safe for the children to return.
• Family life: some households split up for a while, sending grandparents or children to stay with relatives until the house is ready.

Why familiar methods are not always enough

Bleach wipe-downs alone: they disinfect hard surfaces the cloth reaches, but not the gaps behind cupboards, under furniture or the room air, and the harsh smell irritates people with asthma. Never mix bleach with other cleaning products.

Fans and air conditioning: they speed up drying, but if mold is already present, strong airflow can spread spores around the house.

Air freshener, scented candles and charcoal bags: they mask or absorb some odour but do not reduce germs or mold.

Painting over stains: this hides marks briefly, while the mold underneath keeps growing and often reappears within months.

How WHD's ozone disinfection service works

World Health Disinfection (WHD) provides a residential and building ozone disinfection service for homes, condos, hotels, offices, factories, schools and hospitals. According to the service information, ozone (O3) breaks down the cell structures of viruses, bacteria and mold, as well as odour molecules, then reverts to oxygen (O2) with no chemical residue. According to test results certified for the company, with testing by Thailand's Department of Medical Sciences and Intertek (UK), ozone treatment eliminates viruses, bacteria and mold by 99.99%.

1. Prepare the space: the team surveys the home, divides it into zones and checks that every person, pet and plant has left.
2. Release ozone: the generator runs in a room with doors and windows tightly closed.
3. Contact time: ozone spreads through the room and acts on germs in the air and on surfaces the gas can reach.
4. Rest and ventilation: the team waits for the ozone to break down and ventilates as instructed before anyone re-enters.

A typical cycle is about 30 minutes per zone, and jobs of 15,000 baht or more come with a free medical-grade disinfectant spray.

Part 1: Questions about safety

Q: Is ozone dangerous?

A: Ozone is a strongly oxidising gas. That is why it destroys germs, and it is also why nobody should breathe it during treatment, since it can irritate the airways. So the first rule is that ozone treatment must only be done in an empty, closed space with no people, pets or plants inside. When the steps are followed and everyone waits until the rest and ventilation period ends, ozone reverts to oxygen and leaves no chemical residue.

Q: Can we treat a home with a baby, an older person or someone with asthma?

A: Yes, and these are often the homes that benefit most from reduced mold and germs. The condition is that everyone leaves during treatment and returns only after the rest and ventilation period. For very sensitive people, it can help to return a little later than others and open extra windows.

Q: What about cats, dogs, birds or fish tanks?

A: All pets must leave the treated area, including fish tanks, which should be moved out of that zone. If a tank cannot be moved, tell the team so the zones can be re-planned. Pets can stay with neighbours or relatives, or wait with a family member outside the house in a well-ventilated spot.

Q: And houseplants?

A: Plants must be moved out too, because ozone can damage leaves. Put them on the balcony or in front of the house during treatment.

Q: How long must we wait before going back in?

A: A typical cycle is about 30 minutes per zone, but the total time, including preparation, contact time and the rest and ventilation period, depends on the size of the home and the number of zones. The team will give clear timings on the day. Follow their advice and never go in early.

Q: Will electrical appliances, TVs or computers be damaged?

A: Switch off and unplug appliances during treatment, and tell the team about any high-value electronics or collections that are sensitive to air conditions so you can decide together whether to move them. Separately, any appliance that was submerged in floodwater must be checked by a technician before use, whether or not you use ozone.

Q: Will rubber items or brightly coloured fabrics be affected?

A: Some rubbers and fabrics can be sensitive to oxidising gas with long or repeated exposure. If you are worried about particular items, mention them during the survey so they can be moved out of the zone or covered.

Q: Can I do it myself with a machine bought online?

A: The main risks of doing it yourself are misjudging room size and timing, and failing to keep people out during treatment. If you choose to do it yourself, read the manufacturer's manual carefully and treat only empty, sealed rooms. For a flooded home with several zones and vulnerable family members, an experienced team greatly reduces the chance of mistakes.

Part 2: Questions about preparing your home

Q: Should we clean first or use ozone first?

A: Always clean first. The right order is: check electrical safety, remove mud, discard damaged items, wash and disinfect surfaces, dry everything, and only then use ozone. Ozone is an additional step after cleaning; it cannot replace mud removal or drying. If thick mud or puddles remain, the gas can do little for germs buried underneath.

Q: How dry does the house need to be?

A: There should be no standing water and no wet floors, and soaked absorbent materials should be removed or dried first. Fans, dehumidifiers and open windows on sunny days help a great deal. If the walls are still very damp, the team may suggest waiting a little longer.

Q: What should we throw away rather than pay to treat?

A: Mattresses, pillows, rugs, fabric sofas and soft toys that sat in floodwater for a long time, as well as food, medicine and cosmetics that touched floodwater, should be considered for disposal, because contaminated water soaks deep inside where cleaning is very difficult. Ozone suits rooms and air; it does not make ruined items usable again.

Q: What about food in the kitchen and fridge?

A: Throw out food that touched floodwater. Keep good food in sealed containers or move it out of the zone being treated. Keep the fridge door closed as usual.

Q: Should cupboards and drawers be opened?

A: Cupboards that were flooded or smell musty should be left open, along with their drawers, so the gas can reach inside. Unaffected cupboards containing things you would rather not expose can stay closed.

Q: What about the air conditioner?

A: Turn it off during treatment. If it smells very musty, have a technician clean it first, because dirt in the coil is a mold source that has to be removed physically. Ozone then works better on what remains.

Q: Whole house, or just the flooded ground floor?

A: The flooded ground floor is usually the priority, but upstairs rooms used to store belongings rescued from the water, or bedrooms people walked into with wet shoes for days, may also hold damp. The team will help decide how many zones to treat.

Part 3: Questions about results, and what ozone cannot do

Q: Will the mold be gone for good?

A: Ozone reduces mold in the air and on surfaces the gas reaches. But if the source of moisture remains, such as a leaking wall or roof, or a room with no ventilation, mold can return. Deeply embedded mold stains should be scrubbed off or the material replaced. Fixing the cause matters as much as the treatment.

Q: Will the black marks on the wall disappear?

A: Visible stains are physical marks that need scrubbing or wall repair. Ozone does not erase stains, but it helps reduce living germs and musty odour in the space.

Q: After ozone, will nobody in the house get sick?

A: No. Ozone treats spaces; it does not treat or prevent illness in people. Anyone with symptoms after the flood must see a doctor, especially for fever, calf pain, red eyes, severe diarrhoea or breathing difficulty.

Q: If the house smells of paint or chemicals from repairs, is it the same service?

A: If the main problem is the smell of paint, thinner, lacquer or new furniture during renovation, WHD offers an ozone chemical-residue and odour removal service that focuses on odours and VOCs, and the two can be planned together.

Q: When is the best time to do it?

A: After cleaning and drying, and before vulnerable family members move back in for good. If you plan to repair walls or repaint, consider treating after damaged materials have been removed and before walls are closed up or painted, so mold is not sealed inside.

10 reasons Bangkok families choose ozone after a flood

1. The gas reaches every corner: behind cupboards, under beds and through the whole room's air, where wiping cannot go.
2. No chemical residue: ozone reverts to oxygen.
3. Backed by testing: according to test results certified for the company by the Department of Medical Sciences and Intertek (UK); see the ozone disinfection service page.
4. Musty smells tackled at the source, not masked with fragrance.
5. About 30 minutes per zone, so the family can plan a single day out.
6. Suits homes with vulnerable members: when the empty-room rule is followed, children and elders come back to better air.
7. The team assesses zones for you, so you do not have to guess which rooms need it.
8. Fits with the other steps: cleaning, disinfecting and repairs, done in the right order.
9. Less chance of major repairs later: mold is tackled early, before it spreads into materials; read more about the home ozone service.
10. Families can move back in with peace of mind, and confidence is part of recovery too.

Before and after ozone treatment in a flooded home

Example case: ozone day at Mint's house

(An illustrative example, not a review from any specific customer.)

With her questions answered, Mint made a plan. An electrician checked the ground-floor sockets and wiring first. The family discarded the fabric sofa and the swollen wooden cupboard under the stairs, scrubbed the spotted wall, wiped surfaces with disinfectant according to the label, had the air conditioner cleaned, and ran fans and a dehumidifier for two days until the house was dry.

On treatment day, Grandma, the baby and the cat went to stay at Mint's sister's house a few lanes away from the morning. Plants went out front, food went into sealed boxes, and appliances were unplugged. The team divided the house into three zones: the ground floor, the upstairs bedroom and the upstairs storeroom used to keep belongings away from the water. After the rest and ventilation period advised by the team, Mint's husband went in first, opened extra windows, and then brought everyone home in the evening.

Grandma still kept her doctor's appointment for her cough, because ozone is not a treatment. But the family came home to better air, with a weekly moisture checklist stuck on the fridge.

Checklist: preparing your home before and after ozone

Before treatment day

• Have an electrician check the wiring if water reached the sockets.
• Wear gloves, boots and a mask while cleaning.
• Remove mud and discard items ruined by water.
• Wipe surfaces with a disinfectant such as Chemgene HLD4H at the label dilution.
• Dry the house with fans, dehumidifiers and open windows.
• Have the air conditioner cleaned if it smells musty.
• Arrange somewhere for family members and pets to stay.

On the morning

• Move plants, fish tanks and pets out of the area.
• Store food in sealed containers and unplug appliances.
• Open flooded cupboards and drawers.
• Tell the team about valuables or items you are worried about.
• Make sure nobody is in the house before work begins.

After treatment

• Re-enter only after the rest and ventilation period advised by the team.
• Open extra windows before vulnerable family members return.
• Check for smells and damp weekly at first.
• Repair the leaks that cause damp.
• Anyone unwell after the flood should see a doctor.

Quick questions, quick answers

Can we treat downstairs while people sleep upstairs?

Not recommended. The gas can travel up stairwells and through gaps in the house. Everyone should leave the house or stay outside the area set by the team.

Can a condo unit be treated? Should we tell the juristic person office?

Yes, and you should notify the office in advance according to building rules, to make bringing equipment in easier and avoid neighbours' concerns.

How often does it need repeating?

Once the source of damp is fixed, frequent repeats are usually unnecessary. If mustiness returns, always look for the moisture source first.

Is a faint unusual smell after re-entry normal?

Some people notice a faint, distinctive ozone smell at first. Open more windows. If the smell is strong or you feel irritation, leave the area and contact the team immediately.

Can we see the certification documents?

Yes, see WHD's certification documents page.

How do we get in touch?

Phone 065-556-6294, LINE @whd268, or email worldhealthdisinfection@gmail.com.

Still have a question we did not cover? Ask the team

The WHD team is ready to answer your questions, assess your home and plan safe ozone treatment after the 2026 Bangkok floods.

Ask About Post-Flood Ozone Treatment

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

Related links

• Residential and building ozone disinfection service
• Ozone chemical-residue and odour removal
• Chemgene HLD4H medical-grade disinfectant
• Contact us

References

• 2026 Bangkok floods (Wikipedia)
• Al Jazeera: Disaster zone declared across Bangkok
• WHO fact sheets
• CDC: Floods