A story from the field: the air purifier Mum did not want to throw away

Thanakorn is thirty-eight and lives with his sixty-seven-year-old mother in a two-storey townhouse in a soi near Pracha Chuen, in Bangkok's Bang Sue district. His mother has allergies and occasional asthma, so the family bought an air purifier for her ground-floor bedroom, along with two standing fans and an evaporative air cooler for the hottest months.

When the 2026 floods reached their soi, water came into the house at about a hand-span deep and stayed for two days. Mother and son moved upstairs in a hurry. They managed to lift the television and a small fridge, but the air purifier, the two fans and the cooler stayed on the bedroom floor. Their bases sat in muddy water the whole time.

After the water drained away, Thanakorn mopped the floor, wiped the walls and carried every appliance out to dry in the sun in front of the house for three days. His mother wanted the purifier back on immediately. The bedroom smelled musty and she had started coughing at night. Thanakorn was about to plug it in when a neighbor who works as an electrician walked past and stopped him.

"The outside looks dry," the neighbor said, "but there can still be mud and moisture inside the circuit board and the motor. If you plug it in now, it could short out or give someone a shock." That raised two questions the family had not thought about. What should they actually do with appliances that had been underwater? And how could they make the bedroom safe and fresh again for someone with asthma? This article answers both, step by step, in the order that keeps your family safe.

Rule number one: do not plug in a flooded appliance until a technician has checked it

Before we talk about mold and smells, electrical safety comes first. An appliance that has been submerged can still hold water, mud and mineral residue inside its motor, circuit board and switches even after the outside has dried completely. That residue can cause current leakage, short circuits or even fire when the appliance is powered up again.

• Do not plug it in or switch it on "just to test it", even if it is an inexpensive fan.
• Have a qualified electrician check the home's wiring first, especially sockets, cables and breakers on the ground floor that were under water.
• Send flooded appliances to a technician or the manufacturer's service center to decide whether they can be repaired or should be replaced.
• Do not take electrical parts apart yourself, and do not try to dry circuit boards with a hair dryer or an oven.
• If an appliance is under warranty, contact the seller or manufacturer first so you do not lose your warranty rights.

This article is not electrical advice. Whether a particular appliance is safe to use again is a decision for an electrician, a technician or the manufacturer. World Health Disinfection (WHD) takes care of the space: disinfection fogging and ozone treatment of the rooms and home where those appliances live.

Different appliances, different problems

Standing fans and wall fans. The base of a fan contains the motor, switch and wiring. Mud trapped inside the base is also a source of germs and odor. If the technician decides the fan can be used again, plastic blades and guards can usually be removed, washed and wiped with disinfectant according to the manufacturer's instructions.

Air purifiers. HEPA and activated carbon filters that got wet in floodwater should not be reused. The filter material has soaked up dirty water and can become a breeding ground for mold. Instead of cleaning the air, a purifier with a contaminated filter may blow spores and odor back into the room. Fit new filters, of the type specified by the manufacturer, once the technician confirms the unit itself is safe.

Evaporative coolers and humidifiers. These appliances have water tanks and honeycomb pads that are damp even in normal use. After a flood they carry a particularly high risk of bacterial and mold contamination. A technician needs to assess them, and any pad that absorbed floodwater should be replaced.

Vacuum cleaners, rice cookers, microwaves and kitchen appliances. These also need assessment by a technician or service center. Appliances that come into contact with food deserve extra caution.

Power strips and extension cords. Many families simply replace cheap power strips that went under water. The risk is not worth the small saving.

The room where appliances flooded usually has hidden problems too

Even after the appliances have been carried out, the room that sat in floodwater has its own problems that need attention.

• Germs from floodwater. Water that flows into homes is often mixed with sewage. It can carry bacteria such as E. coli, which can cause diarrheal illness, and the bacteria that cause leptospirosis, which can enter the body through cuts and scratches.
• Mold on walls and furniture. The lower part of walls, bed legs, wooden wardrobes and mattresses that sat on the floor are where mold usually appears first, often within just a few days.
• A musty smell that will not go away. The smell of mud and drains soaks into curtains, bedding and porous materials and lingers long after the floor looks clean.
• Allergy sufferers and older people feel it first. Mold spores can trigger coughing, sneezing, blocked noses and asthma symptoms, especially at night when the bedroom door is closed.

Here is the catch that many families miss. The natural reaction is to switch on the air purifier to deal with the musty smell. But if the filter has been soaked and the room still contains sources of mold, a single purifier cannot solve the problem at its root. It ends up fighting a losing battle around the clock.

Why familiar fixes are not enough

• Blowing the room dry with fans. A fan that was flooded must not be used until it has been checked. Even with a different fan, moving air helps things dry faster, but it does not kill germs or break down odors.
• Pouring on strong bleach. The sharp fumes of bleach in a closed room can irritate the airways, which is the last thing someone with asthma needs.
• Incense and air fresheners. Smoke and fragrance can themselves trigger allergies, and the musty smell is still there underneath.
• Changing the purifier filter and hoping for the best. If there is still mold on the walls and curtains, the purifier will work constantly without ever catching up.

None of these steps is useless on its own, but none of them deals with germs on surfaces and odor in porous materials at the same time. That is the gap that professional disinfection and ozone treatment are designed to fill.

What to keep and what to throw away from a ground-floor bedroom

• Foam mattresses and pillows that sat in floodwater. They absorb dirty water deep inside and are very difficult to clean thoroughly. Most should be discarded, especially in a home with an allergy sufferer.
• Curtains and bed linen. Wash them in hot water if the fabric allows it, and dry them completely. If a smell or mold stains remain, replace them.
• Solid wood and metal furniture. These can often be kept after cleaning and thorough drying. Plywood or particleboard that has swollen with water usually needs to be replaced.
• Cardboard boxes, books and papers. Wet boxes should go. Photograph important documents first and then look into ways to recover them.

Removing the items that act as mold reservoirs before disinfection and ozone treatment gives better results that last longer. Treating a room full of soaked foam and cardboard is like mopping the floor while the tap is still running.

Our process for rooms where appliances were flooded

1. Site survey. The team checks how high the water rose, where mold stains and odors are strongest, and whether an electrician has inspected the home's wiring. If not, we recommend arranging that first.
2. Clearing the space. Flooded appliances are moved out of the room so that a technician can assess them. Mud is removed and damaged items, such as soaked foam mattresses, rugs and cardboard boxes, are discarded.
3. ULV disinfection fogging. Our disinfection service applies CHEMGENE HLD4H as a fine mist that reaches room corners, the space under the bed, skirting boards and the back of wardrobes.
4. Ozone treatment. The room is closed and an ozone generator runs at a controlled dose matched to the room size, reducing mold spores and breaking down odor molecules in the air, curtains and porous materials. During treatment there must be no people, pets or plants in the room.
5. Protecting remaining electronics. Televisions, computers and other electronics that were not flooded should be moved out or covered before ozone treatment, because some rubber and plastic parts are sensitive to ozone.
6. Ventilation. Doors and windows are opened until the ozone has broken down and there is no sharp smell, before older people or allergy sufferers return to the room.
7. Re-check and advice. The team checks the smell and condition of the room again, gives advice on controlling humidity, and suggests the right moment to bring the technician-approved air purifier back with fresh filters.

The recommended order of work for a Bang Sue home

1. An electrician checks the home's wiring and the ground-floor sockets.
2. Flooded appliances go to a technician or service center for assessment.
3. Mud is removed, the floor is washed and soaked items are thrown away.
4. WHD disinfects surfaces and ozonates the room.
5. The room is fully ventilated.
6. Appliances confirmed safe by the technician come back in, fitted with new filters, and only then are they switched on.

Following this order means the air purifier that returns to the bedroom is not fighting mold still hiding in the room, and it is not blowing dirt from an old filter back into the air. It also avoids paying for the same job twice because the steps were done in the wrong order.

Why fogging and ozone work as a pair

People often ask whether they need both disinfection fogging and ozone treatment, or whether one is enough. In a room that has been flooded, the two steps do different jobs.

Fogging deals with surfaces. Floodwater leaves behind a thin film of silt, organic matter and bacteria on the floor, the lower walls, furniture legs, skirting boards and the bottom of doors. Once the mud has been cleared and the surfaces cleaned, a fine disinfectant mist settles evenly on them, including the awkward places behind and beneath furniture that a cloth never quite reaches. This is the step aimed at the germs carried in by the water.

Ozone deals with air and porous materials. Odor molecules and mold spores do not stay on hard surfaces. They work their way into curtains, fabric headboards, wooden furniture and the gaps between materials. Because ozone is a gas, it can travel into those spaces and react with odor molecules and microorganisms there. That is why a bedroom can still smell musty after being scrubbed from top to bottom, and why the difference after ozone treatment is something families can actually notice when they walk back in.

Neither replaces fixing the source of moisture. If a wall is still soaked or a pipe is leaking, that must be repaired. Treatment works best in a room that has been cleaned, cleared of ruined items and given time to start drying out.

Looking after an allergy sufferer during recovery

When someone in the family has allergies or asthma, the recovery period needs a little extra planning. These suggestions are general and practical, not medical advice. Anyone with worsening symptoms should see a doctor.

• Keep them away from the clean-up. Scrubbing, removing mud and carrying out wet items stirs up dust and spores. If possible, the allergy sufferer should stay upstairs or with relatives while the heavy work is done.
• Plan where they will sleep. During ozone treatment and ventilation, the room cannot be used. Arrange another room for those nights in advance so nobody is tempted to go back in early.
• Bring back only clean, dry items. Bedding, pillows and soft toys should be washed and fully dried, or replaced, before they return to the treated room.
• Watch humidity. A simple humidity meter helps you see whether the room is drying. Keeping the room aired during the day makes a difference in the weeks after the flood.
• Pay attention to night-time symptoms. If coughing or wheezing at night does not improve after the room has been treated and ventilated, talk to a doctor and let us know so we can look for remaining sources of mold.

The first month after treatment

Walls and floors that sat in water keep releasing moisture for weeks. A few simple habits help stop the musty smell from returning.

Air the room every morning. Open the windows for a while before the day gets hot. Fresh air carries away humidity that the walls are still giving off.

Leave gaps behind furniture. Do not push the bed and wardrobe tightly back against the walls straight away. A small gap lets air move and makes it easier to spot new mold early.

Change filters on schedule. Once the purifier is back in service with new filters, follow the manufacturer's replacement schedule, and check them more often during the first month.

Call early, not late. If you notice new dark spots, a returning smell or symptoms getting worse, contact us for a re-check. Small problems are quicker and cheaper to deal with than large ones.

A note for landlords and tenants in Bang Sue

Bang Sue has many small apartment buildings, rooms for rent and dormitories for workers and students. In rented rooms, fans and sometimes air purifiers or coolers are supplied by the landlord. After a flood, it is worth agreeing clearly who arranges the electrical check, who replaces appliances that cannot be saved and who books the room treatment. Tenants should not plug in landlord-supplied appliances that were flooded until they have been checked, and landlords benefit from treating several rooms in one visit rather than one at a time.

For buildings with several flooded ground-floor rooms, our team can survey the whole floor, plan disinfection and ozone treatment room by room, and help you schedule it so tenants are inconvenienced as little as possible.

10 reasons Bang Sue families trust WHD

1. A clear division of work: electricians handle appliances, WHD handles the space. We do not take on work outside our role or take risks with your home's safety.
2. ULV disinfection fogging reaches under beds and behind wardrobes where wiping cannot.
3. Ozone treatment breaks down musty odors in the bedroom rather than covering them.
4. We use CHEMGENE HLD4H for surface disinfection.
5. Care for homes with older people and allergy sufferers, with clear guidance on ventilation time before re-entry.
6. Controlled ozone doses, with advice on covering or removing electronics.
7. Help sequencing our work with your electrician so nothing has to be done twice.
8. An optional dust mite removal service for mattresses and pillows that can be kept.
9. An optional mosquito spraying service around the house while water is still standing in the soi.
10. Easy to reach by phone and LINE, covering Bang Sue, Pracha Chuen, Wong Sawang, Tao Pun and nearby areas.

Before and after

Customer voice (example scenario)

"I was one second away from plugging the purifier in. Thank goodness my neighbor stopped me. The technician said one fan had to be replaced and the purifier was fine but needed new filters. After the team disinfected and ozonated Mum's bedroom, the musty smell was mostly gone and she has been sleeping much better."

— Thanakorn, townhouse near Pracha Chuen, Bang Sue (example scenario)

Frequently asked questions

Q: My fan has dried in the sun for days. Can I plug it in now?
A: Not until an electrician or service center has checked it. Moisture and mud can remain inside the motor and circuit board even when the outside is completely dry.

Q: Can I wash and reuse an air purifier filter that got wet in floodwater?
A: We do not recommend it. HEPA and carbon filters that absorbed dirty water should be replaced with the type specified by the manufacturer.

Q: Does WHD repair or disinfect the inside of appliances?
A: No. Work inside electrical appliances is for a technician or service center. WHD disinfects and ozonates the rooms and spaces in your home.

Q: Can you ozonate a room with a TV and computer in it?
A: Yes, using a controlled dose. We recommend moving or covering electronics before treatment.

Q: When can an older person with asthma go back into the room?
A: After ventilation, once there is no sharp ozone smell. The team will tell you when. If anyone feels unwell, please consult a doctor.

Q: Do you serve rented rooms and dormitories in Bang Sue?
A: Yes. We treat houses, townhouses, rented rooms and dormitories in Bang Sue and nearby areas. Contact LINE @whd268.

Electrical safety first, then a room you can breathe in

Book a survey for your home or rooms in Bang Sue, Pracha Chuen, Wong Sawang and nearby areas.

Book Ozone Treatment - Click Here

See Disinfection Service - Click Here

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

Related links

• Residential ozone disinfection
• Ozone odor and chemical residue removal
• Master Ozone Generator
• All articles

Health reference: World Health Organization (WHO): Floods · Department of Disease Control, Thailand