A typical scenario (an illustrative story based on common situations, not a review from a specific customer)

One week before the holiday crash course

Teacher Ton runs a maths and science tutoring school in a three-storey shophouse in Lat Phrao. Most of his students come from schools nearby and from communities around Khlong Chan. The ground floor has the reception desk, a waiting corner for parents and a small primary classroom with carpet tiles and low Japanese-style tables. The second and third floors are air-conditioned classrooms with acoustic panels on the walls, whiteboards, projector screens, shelves of worksheets and exercise books, and a records room holding years of past exam papers.

Late September is the busiest point of his year. The October-break crash courses are fully booked, parents have paid in advance and timetables went out to the parents' LINE group at the start of the month. Then, on the night of 25 September 2026, after two days of rain, the road outside flooded. Water came into the ground floor almost knee-deep, and power to the building was cut for several days for safety.

When the water dropped and the power returned, the damage was not confined to the ground floor. The carpet tiles in the primary room were sodden and foul. The bottom row of bookshelves had swollen. Mud had pushed up through the ground-floor toilet drains. And the second floor, which the water never reached, smelled powerfully musty: its sealed, air-conditioned classrooms had sat for days without power for the AC and without any ventilation. White patches of mold dotted the acoustic panels, and stacks of worksheets on the desks smelled of damp paper.

In the parents' group, questions poured in: "Is the course still on?" "Have the classrooms been disinfected? My son has allergies." "Lots of kids are getting sick right now. I'm worried they'll pass it around in class." Ton had less than a week, and he knew that wiping desks and spraying air freshener was not the answer parents wanted. This article looks at where post-flood germs and mold hide in tutoring schools, why sealed classrooms that stayed dry can still be a problem, and how ozone disinfection of empty rooms helps a school get ready to reopen.

The late-September 2026 Bangkok floods and private tutoring

According to news reports, Bangkok received roughly 300 mm of rain in about 48 hours between 24 and 27 September 2026. On 26 September the BMA declared all 50 districts a disaster zone. Eastern Bangkok was hit hardest, with Khlong Chan and Bueng Kum mentioned. Governor Chadchart Sittipunt said the canals were full and drainage would take two to three days after the rain stopped. Reports noted three deaths, and our sympathies go to their families.

As of 30 September, some roads, including Si Burapha and Lat Phrao, still had 20 to 40 cm of water. Thai media compared the event with the 2011 floods, and one business report cited a Chamber of Commerce estimate of about 12,300 million baht in damage.

The timing hit tutoring schools especially hard, because it fell just before the end of the first semester, the season for intensive courses: mid-term revision, second-semester foundations and entrance-exam preparation. Most tutoring schools operate from shophouses, commercial buildings or the upper floors of malls and community malls, in small air-conditioned classrooms with windows kept shut against noise and walls lined with sound-absorbing materials that hold moisture well.

Where germs and mold hide in a tutoring school after a flood

Tutoring schools differ from regular schools: rooms are small and sealed, air conditioning runs constantly, students sit close together for hours, and groups rotate through from morning to night. After a flood and a long building closure, the risk is not limited to the floor the water reached.

Sealed classrooms without power: an unexpected incubator

When power is cut for days, the air conditioning that normally pulls moisture out of the room stops. Humidity from the flooded floor below and the rainy season builds up in sealed rooms, temperatures climb, and mold thrives. Upper classrooms that never got wet can grow mold on walls, gypsum ceilings and furniture within days. WHO and CDC guidance is to clean and dry within 24 to 48 hours to limit mold, but a building without power and closed to access inevitably misses that window.

Acoustic panels, carpet and curtains

Foam or fabric-wrapped fibre acoustic panels are porous, with a huge surface area; they absorb moisture and are hard to clean. Carpet tiles and rugs in young children's rooms trap mud and germs in the fibres and the backing once soaked. Heavy blackout curtains for projector rooms dry slowly and hold many spores. These materials release mold spores into the air students breathe throughout every lesson.

Air conditioners and ducts

Split-type units in classrooms have cooling coils and drip trays that are always damp. After days switched off in a hot, humid room, slime and mold in the drip tray increase. The first time the AC comes back on, the cold air carries spores and mustiness across the room. Schools in malls on central air systems have ducts that can hold moisture too.

Books, worksheets and piles of paper

A tutoring school stores far more paper than a normal office: worksheets, prep books, past papers and exercise books. Paper absorbs moisture from the air and feeds many kinds of mold, so stacks in a closed room smell musty and shed spores even if they were never submerged.

Toilets, sinks and water dispensers

Ground-floor toilets are where sewage can back up during a flood, leaving silt and faecal bacteria that cause diarrhoea. Drinking-water dispensers left without power for days, and filters that sat in stagnant water, should be cleaned and the filters replaced before students use them.

Infections that spread easily in crowded classrooms

The rainy season is when respiratory illnesses such as influenza, and hand, foot and mouth disease in young children, are common in Thailand. Tutoring rooms where students sit shoulder to shoulder for hours, sharing desks, whiteboard markers and tablets, make it easy for germs to pass around. After the flood, many children are also worn out from helping their families move belongings or staying elsewhere temporarily, which makes clean air and surfaces even more important.

Who is most at risk

• Young children in primary and kindergarten classes, who sit on carpets, put hands in mouths and have developing immune systems.
• Students with allergies and asthma, whose symptoms can flare with mold spores in sealed AC rooms.
• Students preparing for major exams, for whom a week of illness can affect results.
• Teachers, tutors and staff who clean the building after the water drops and talk all day in classrooms.
• Parents and grandparents who wait in the ground-floor lounge, the floor that flooded.

Important: if teachers or staff who helped clean develop fever, headache, muscle pain (especially in the calves), red eyes or diarrhoea after wading or shovelling mud, they should see a doctor and mention flood exposure, as these can be signs of leptospirosis. Students with fever, cough, rashes or mouth ulcers should stay home and see a doctor. Ozone treatment reduces germs in the environment; it is not a medical treatment.

What the flood costs a tutoring school

Student health is parents' trust

Parents leave their children with you for hours each day. If a child comes home sneezing nonstop, has an asthma flare, or several students in one class fall ill together, the parents' LINE group will hear about it immediately, even if the real cause lies elsewhere.

Courses already sold that cannot be postponed

Holiday courses run in a fixed window. Postpone them and students return to school with no time to catch up. You may have to refund fees or schedule make-up sessions when tutors are busy, hurting both income and every tutor's timetable.

Repair and replacement costs

Carpet, acoustic panels, curtains, plywood bookshelves, teaching materials and submerged electronics are all major costs for a small school, and rent keeps running while classes are suspended.

Reputation in a competitive market

Parents have plenty of choice and compare schools constantly, often on word-of-mouth. A school that handles the post-flood period systematically and communicates openly gains trust, while one that stays silent or reopens with musty classrooms may lose students to a rival.

Concentration and results

A musty classroom with heavy air that leaves noses blocked and eyes itchy is not a place to focus, especially in crash courses that demand hours of concentration. Air quality directly affects what a tutoring school sells: students' results.

Common fixes, and why they fall short

• Wiping desks with alcohol and reopening. Wiping touch points is good, but it does nothing about mold on acoustic panels, carpet, ceilings or in the room air.
• Air freshener or charcoal odour absorbers. These reduce or mask smells briefly while the source remains, and strong fragrance in a sealed AC room can trigger allergic children.
• Running air purifiers. Purifiers filter some dust and spores from the air, but they do not deal with growth on carpet, walls and paper, which keeps releasing new spores.
• Turning the AC to maximum to drive out humidity. If coils and drip trays have not been cleaned, you are blowing days of accumulated growth into the classroom.
• Painting over mold on walls. Paint hides it briefly; if the wall is still damp, mold returns, and fresh-paint smell in a sealed classroom is another problem for children.
• Pouring bleach on carpet. It stains and damages carpet, does not reach the backing, and leaves fumes lingering in a closed room, unsuitable for children.

Tutoring classrooms are sealed spaces full of porous materials: fabric, foam, carpet and paper. Methods that work only on some surfaces or only on part of the air leave gaps. What is missing is a step that treats the air and surfaces in every corner of the room at once, after cleaning and drying.

WHD ozone disinfection for tutoring schools and tutor centres

World Health Disinfection (WHD) provides residential and building ozone disinfection for homes, condos, hotels, offices, factories, schools and hospitals, including tutoring schools and tutor centres with several classrooms in one building. Ozone (O3) is a strongly oxidising gas. Released into a sealed classroom, it spreads throughout the room, into the air, onto acoustic panels, under desks, behind bookshelves and into gaps a cloth cannot reach. It breaks down the cell structures of viruses, bacteria and mold, as well as odour molecules, then reverts to oxygen (O2) with no chemical residue on desks or the floor where children sit.

According to the test results the company has had certified, WHD's ozone service was tested by Thailand's Department of Medical Sciences and Intertek UK, with a stated 99.99% elimination of viruses, bacteria and mold. Schools can refer to the certification documents when communicating with parents.

Safety rules: ozone treatment is done only in empty, closed rooms. Students, teachers, staff, parents, pets, plants and fish tanks must all be out of the area, and no one returns until the rest and ventilation period is over. Schedule treatment on a day or time with no lessons, such as the day before a course starts or after the last class of the day.

How the job runs in a tutoring school

1. Survey and plan around the timetable. The team walks every floor with the owner, zoning each classroom, the records room, parents' lounge, staff room and toilets, then sequences the work to fit the course start date.
2. Readiness check. Mud removed; soaked carpet and acoustic panels stripped out; floors and walls washed and reasonably dry; air conditioners cleaned or scheduled for cleaning.
3. Clear the area. Everyone leaves the zone; computers and projectors are switched off and unplugged; plants and fish tanks are moved out.
4. Open cupboards and storage. Filing cabinets and drawers are opened and usable worksheets spread out loosely so gas can reach them. Doors, windows and vents leading out of the zone are closed.
5. Run the ozone generator. A standard cycle is about 30 minutes per zone, covering filling, contact time and a rest period before ventilation. Larger classrooms may take longer.
6. Rest and ventilate. Open doors, windows and extractor fans as the team advises, until you are told re-entry is safe.
7. Reset and prepare for the course. Wipe desks and high-touch points again, space desks where possible, and switch on the cleaned AC before students arrive.

For ozone jobs from 15,000 baht, WHD includes a free medical-grade disinfectant spray, useful between lessons for door handles, whiteboard markers, AC remotes and the reception counter.

10 reasons tutoring schools should book ozone disinfection before courses resume

1. Sealed classrooms need whole-room treatment. Ozone disinfection of tutoring classrooms reduces germs in the air and on surfaces in one pass.
2. It reaches acoustic panels and ceilings, which cannot be scrubbed and are major sources of spores.
3. It covers upper rooms that stayed dry but sat sealed for days, which are often overlooked despite the moisture build-up.
4. No chemical residue on desks. Ozone reverts to oxygen, so children can rest hands, arms and snacks on desks without chemical film.
5. It removes mustiness from paper and fabric, giving fresher air for long, focused sessions.
6. About 30 minutes per zone, so a school can be treated in a day before a course or after the last class.
7. It is backed by testing. Company-certified results from the Department of Medical Sciences and Intertek UK state 99.99% elimination of viruses, bacteria and mold.
8. It gives parents evidence, not reassurance. You can tell the LINE group exactly what each room went through, rather than just "we cleaned".
9. It helps children with allergies and asthma, as fewer spores and less mustiness make class more comfortable for them.
10. It protects courses already sold and your school's name. Book a survey with WHD's ozone disinfection service; jobs from 15,000 baht include a free medical-grade disinfectant spray.

Before and after ozone treatment in a tutoring school

Note: results depend on site conditions and on cleaning and drying beforehand. Carpet, acoustic panels and papers damaged by sewage should be replaced.

Example case: an English school on the second floor of a Bueng Kum commercial building

Example case (an illustrative scenario based on common jobs, not a testimonial from a real customer)

Teacher Prae runs an English school for primary and lower-secondary students on the second floor of a commercial building: four classrooms, a small one-to-one room and a carpeted reading corner stocked with English picture books. During the flood, the building's ground floor and car park went under and the whole building lost power for several days. Not a drop of water reached her school, yet when she opened the door after the power came back, the mustiness was so heavy she rushed to open the windows. The reading-corner carpet and the spines of many picture books had grown mold, and every air conditioner smelled bad when switched on.

She had every AC unit cleaned, separated out moldy books, threw away the reading-corner carpet, wiped down all desks and chairs, and ventilated for two days. Then she booked WHD for a Sunday with no classes. The team divided the school into six zones, switched off and unplugged the computers, opened every teaching-supplies cupboard and drawer, and treated one room at a time. After ventilation, she rebuilt the reading corner with wipe-clean plastic cushions instead of carpet.

That night she posted a brief summary in the parents' LINE group: the steps taken, that moldy books had been removed, and a request that children with fever or a cough stay home for now. Many parents replied with thanks, and the holiday course started on schedule the following week.

Post-flood recovery checklist for tutoring schools

Before you call the ozone team

• Have an electrician check wiring, sockets and submerged equipment before use, especially on the ground floor.
• Wear boots, rubber gloves and a mask while removing mud and carpet, and cover any wounds.
• Strip out carpet, acoustic panels and curtains that soaked in sewage or show heavy mold.
• Sort books, worksheets and documents; keep only what is needed and completely dry.
• Remove mud and wash floors, walls, toilets and drains with clean water and detergent.
• Disinfect cleaned hard surfaces with a suitable product such as Chemgene medical-grade disinfectant, following label dilution and contact time.
• Have every air conditioner cleaned, including coils, drip trays and filters.
• Clean water dispensers and replace drinking-water filters, then ventilate and dehumidify until dry.

On treatment day

• Book a day with no lessons, or after the last class.
• Everyone leaves the zone; move plants and fish tanks out.
• Switch off and unplug computers, projectors and other electrical equipment.
• Open filing cabinets, drawers and every inner door, and warn neighbours or building management if vents are shared.

After treatment

• Ventilate as long as the team advises before anyone re-enters.
• Wipe desks, door handles and shared equipment again before the course starts.
• Replace carpet in young children's areas with wipe-clean materials.
• Set up handwashing or alcohol-gel points at each classroom door.
• Ask parents to keep children with fever, cough, rashes or mouth ulcers at home.
• Control humidity and check damp corners and the records room weekly for the first month.

FAQ: ozone disinfection for tutoring schools after a flood

Can we treat one room while classes run next door?

Not recommended. Ozone treatment needs empty rooms, and neighbouring rooms connected by vents may receive gas. Book a time with no lessons in that zone or any connected zone.

Our upper classrooms stayed dry. Do they need treatment?

If the building was sealed for days without power or ventilation, upper rooms can build up moisture and grow mold. If they smell musty or show spots, include them. The team will assess on site.

Can moldy books and worksheets be used after ozone?

Papers soaked in sewage or visibly moldy should be discarded. Ozone reduces germs in the room and on surfaces but does not repair damaged paper. Keep essential documents completely dry and in sealed containers.

Does ozone replace cleaning the air conditioners?

No. A technician should clean coils and drip trays. Ozone is an extra step after cleaning, never a replacement for AC servicing, mud removal or drying.

How long does it take, and when can we teach again?

A standard cycle is about 30 minutes per zone. A school with four to six classrooms is usually done within a day, including ventilation. The team will estimate the real time during the survey so you can plan.

What should we tell parents?

Be specific and honest: damaged materials removed, surfaces washed and disinfected, AC cleaned, rooms dried, and ozone disinfection done in empty rooms, plus a request to keep sick children home. Avoid promising "100% germ-free" classrooms; no method can guarantee that.

Get your classrooms ready before the first student arrives

Book a WHD survey of your tutoring school. We plan treatment around your timetable and carry out ozone disinfection in empty rooms after cleaning and drying, so your courses can start on schedule.

Book a Classroom Ozone Survey

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

Ozone jobs from 15,000 baht include a free medical-grade disinfectant spray.

Related links

• Residential and building ozone disinfection
• Ozone removal of chemical residue and odours, for paint and new-carpet smells after renovation
• Chemgene HLD4H medical-grade disinfectant
• Contact us

References

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