A typical scenario (an illustrative story based on situations we commonly see, not a review from any specific customer)

The giraffe mural looked wonderful. Teacher Joy opened the door and had to step straight back out.

Teacher Joy runs a small private kindergarten in Bueng Kum, on the eastern side of Bangkok. From 24 to 27 September 2026, heavy rain fell almost without pause. According to news reports, around 300 mm of rain fell in roughly 48 hours, the Bangkok Metropolitan Administration declared all 50 districts a disaster zone on 26 September, and eastern areas such as Bueng Kum and Khlong Chan were among the hardest hit. The school closed at short notice, teachers phoned parents one by one, and water spread through every ground-floor classroom.

When the water went down, the sight was heartbreaking. Foam crawling mats had floated into a corner and stuck together. Picture books had turned to pulp. Cuddly toys were soaked with mud, the plywood shelves had swollen, and the walls that once displayed the children's paintings carried a brown tide mark at an adult's knee height. Teachers and volunteer parents shovelled out the mud, washed everything and threw away what could not be saved. The school then hired painters to redo the entire ground floor, adding giraffes, elephants and trees to the walls, brighter than before. New rubber safety flooring was glued down, and new child-sized tables, chairs and shelves were ordered.

Two days before the reopening date the school had announced to parents, Teacher Joy walked into the K1 classroom to set up the toy corner. When she opened the door, a wave of paint and adhesive smell rolled out, and she had to step outside to breathe. She pictured three-year-olds sitting on that floor, napping in the room next door and spending hours there every day. That evening, a message appeared in the parents' LINE group: "The classrooms have been repainted. Will the kids be breathing in paint fumes?" Teacher Joy could not answer. She had nothing to go on except her own nose.

This article is for directors of kindergartens, nurseries and early childhood centres repainting and renovating after the flood. It explains why young children are more sensitive to chemical odours than adults, which common fixes fall short, and how ozone chemical-residue treatment can help a school reopen with greater confidence.

Where kindergarten classroom odours come from, and why small children are more sensitive

Sources of VOCs in early-years classrooms

Volatile organic compounds (VOCs) are chemicals that evaporate into the air at room temperature. In a kindergarten freshly renovated after a flood, the main sources are wall paint and the paints used for decorative murals, the clear varnish brushed over murals so they can be wiped clean, the adhesive used to lay rubber tiles or vinyl flooring, shelves and cupboards made from plywood or particleboard, sealant around the children's washbasins, and new cushions, nap mattresses and plastic toys that have just been unwrapped. All of these release the most vapour in the period immediately after installation.

Hidden mustiness and floodwater smells

Ground-floor classrooms that sat in water for days often keep moisture inside the walls, under built-in shelving and in the cupboards where nap mattresses are stored. If walls are painted before they are completely dry, mustiness and mold return later. Urban floodwater also carries mud, sewage and oil, and these smells linger in door frames, skirting and drains. On top of that comes the smell of the large amounts of cleaning products used to recover the school.

Why young children are affected more

Young children breathe faster than adults and take in more air relative to their body weight. Kindergarten children spend much of their day close to the floor: sitting in circles, crawling, playing on mats and napping on mattresses, right at the level of newly laid flooring and adhesive. They put their hands and toys in their mouths and cannot always describe how they feel. A teacher may simply see a child who is grizzly, rubbing their eyes, coughing or refusing to nap, without realising the room's air might be a factor. Children with existing allergies or asthma need extra care. Teachers and assistants who are in the room all day, including pregnant staff, are exposed too. Common symptoms include headaches, stinging eyes, nose and throat irritation, nausea and restless sleep.

If a child or staff member has persistent symptoms, they should see a doctor. Anyone who waded through floodwater and later develops fever or calf pain should seek medical care promptly because of the risk of leptospirosis, and children with diarrhoea after the flood should also be seen by a doctor. Treating indoor odours is not medical treatment.

What happens if a school reopens while classrooms still smell of paint

Children's health and comfort. Children in a room with strong chemical odours may be irritable, get headaches or fail to settle at nap time, which affects learning and mood for the rest of the day. Reopening after a flood is also a time when many children are still adjusting to stress at home. The classroom should be the safest space they have.

Parents' confidence. Parents of young children notice everything. A single question about paint smell in the LINE group can become a worry for the whole class. Some families may keep their child home for longer or start looking at other schools.

Income and operations. Private kindergartens rely mainly on fees. Postponing reopening, or losing families to other schools, hits finances directly. According to news reports, a Thai business report cited a Chamber of Commerce estimate of around 12,300 million baht in damage from these floods. A small school that has just paid a large repair bill has little room for another setback.

Time. Waiting for odours to fade naturally, without any active measures, can take weeks, while many parents need to return to work and need childcare quickly.

Teachers and staff. Teachers who have worked hard for days to rescue the school then face questions they cannot answer, in rooms that give them headaches. Team morale matters as much as anything else.

Why the usual fixes are not right for young children's classrooms

Air freshener and fragrance. Fragrance only masks paint smell temporarily and adds more volatile chemicals to a room where children breathe all day. That is exactly what an early-years classroom should avoid.

A few hours of fans and open windows. Ventilation genuinely helps and should be done. But while the outside air is still humid and some streets still have standing water, opening windows can bring moisture back in, and a few hours is not enough to clear compounds still evaporating from walls, floors and furniture.

Bamboo charcoal or baking soda bags. These help a little inside cupboards or small corners, but a whole classroom with several freshly painted walls and a complete rubber floor is far beyond a few bags, and the bags themselves become something small children might pick up and play with.

Painting over water stains again. If the wall is still damp, a new coat traps the moisture. Stains and mold come back, along with additional VOCs from the extra layer of paint.

Mopping with strong disinfectant every day. Surface disinfection is essential in early-years settings, but products must be used according to the label, including any rinsing or wiping it specifies. Overuse does not improve the air and adds chemical odour at exactly the level where children crawl.

Trusting the teachers' noses. Staff who are in the building every day get used to the smell very quickly and believe it has gone, while parents walking in for the first time still notice it clearly. Without measurable data, it is hard for a school to answer parents' questions.

Walking the school through a child's eyes: where odours collect

Classrooms. Murals and varnish on the walls, rubber flooring glued across the whole room and new low shelving all emit at child height. Classrooms are usually the largest emitting space in the school.

Nap rooms. These are often small, darkened and closed so children can sleep, which is exactly the kind of room where odours build up. Mattress cupboards that sat in floodwater are a common hidden source of mustiness.

Children's toilets and washrooms. New sealant around basins and toilets, combined with drains that carried floodwater, can produce a mix of chemical and sewer smells.

Dining area and kitchen corner. Food areas need special care. Repainting, new tables and cleaning chemicals here should be planned so that no food or milk is stored in the space while work and treatment take place.

Corridors and the entrance. This is where parents form their first impression at drop-off. A strong paint smell here can shape a parent's view of the entire school, even if the classrooms themselves are fine.

Mapping the school this way helps the WHD team plan treatment zones, choose which rooms need extra attention, and present TVOC results to the school in a way that makes sense to parents.

The answer for kindergartens: WHD ozone chemical-residue and odour removal

World Health Disinfection (WHD) provides ozone treatment for chemical residue and odours in spaces that have just been painted, re-floored or refurnished. According to the service information, ozone (O3) breaks down odour molecules at the source instead of masking them. It targets paint, thinner, epoxy and lacquer odours, VOCs and musty smells, and also helps deal with bacteria, viruses and mold in the air and on surfaces the gas can reach. When the process ends, ozone reverts to oxygen and leaves no residue, and the space is ready to use about two hours after treatment.

For a school, the most valuable part is data it can share with parents. According to the service information, the WHD team measures TVOC (total volatile organic compounds) with calibrated instruments before and after treatment, uses a Master Ozone Generator, and serves many kinds of premises, including homes, condos, offices, factories, construction sites, hotels, storage facilities and vehicles. School directors can then answer the LINE group with information rather than a simple "it doesn't smell any more".

How ozone treatment works in a kindergarten

1. Survey with the school director. Identify classrooms, nap rooms, children's toilets, mattress stores, the dining area and corridors that were painted or re-floored.
2. Measure TVOC before treatment. Record a baseline for each room for comparison.
3. Prepare the rooms. Remove food, milk and snacks. Store paper artwork you want to keep, and tell the team about any especially delicate materials.
4. Empty and seal the area. No children, teachers, parents, classroom pets such as fish or rabbits, and no potted plants. Close all doors and windows.
5. Release ozone for the set time. Nobody enters during treatment.
6. Rest and ventilate. Allow the ozone to revert to oxygen. According to the service information, the space is ready about two hours after treatment.
7. Measure TVOC after treatment and hand over. Compare readings and receive advice on classroom care during the first week back.

The most important safety rule: ozone treatment is done only in an empty, closed space. Children, teachers, parents, pets and plants must all be out of the area, and nobody re-enters until the rest and ventilation period is over. Schools should schedule treatment on a weekend or before reopening, and never on a day when children are in the building.

Ozone is a step after mud removal, cleaning, discarding contaminated items and drying the rooms. It does not replace cleaning flood-exposed toys, and it does not replace waiting for paint to dry as the manufacturer specifies. For surfaces children touch often, such as tables, door handles, stair rails and washed plastic toys, schools can use the Chemgene HLD4H medical-grade disinfectant at the dilution and following the directions on the label.

10 reasons kindergartens should ozone-treat after repainting

1. Young children are the most VOC-sensitive people in the building. Reducing vapours before they return targets the group most at risk.
2. It breaks odours down without adding fragrance. According to the service information, ozone reacts directly with odour molecules, so classrooms do not need air freshener.
3. Paint, varnish and mat adhesive in one treatment. See the chemical-residue ozone service page for details.
4. Before-and-after TVOC data for parents. Turn a worried LINE message into reassurance.
5. No residue on floors where children crawl. Ozone reverts to oxygen.
6. It reaches nap rooms and mattress stores. Closed rooms where mustiness and chemical smells tend to build up.
7. It helps with airborne microbes left from the flood. According to the service information, ozone helps deal with bacteria, viruses and mold wherever the gas reaches, complementing surface cleaning.
8. It fits a weekend before reopening. The space is ready about two hours after treatment, according to the service information, so reopening need not be delayed for long.
9. More comfortable rooms for teachers. Fewer headaches while preparing and teaching.
10. A clear final step to explain to parents. Clean, dry, paint, ozone, then reopen. Check availability on the WHD service page.

Before and after ozone in a kindergarten classroom

Note: results depend on the type of paint, flooring material, wall moisture and time since painting. The team assesses each room and reports what it actually measures.

Example case: a Bueng Kum kindergarten answers the parents' LINE group

Example case, shown to illustrate how the work is done, not a verified review from a specific customer.

After the paint smell in K1, Teacher Joy contacted WHD and arranged a Saturday survey. The team walked every room. The classroom with the varnished giraffe mural had the highest TVOC reading, while the inner nap room smelled musty because the mattress cupboard was still damp. The team advised discarding the mattresses that had been in floodwater, opening the cupboard and running a dehumidifier first, then including the room in the treatment.

On Sunday, teachers removed milk, snacks and the children's artwork, moved the classroom fish tank to the office building and carried potted plants off the corridor balcony. The team sealed the area, posted "Do not enter" signs and treated zone by zone. After the rest and ventilation period, TVOC was measured again. Most rooms showed a clear reduction, including the varnished mural room, though the team recommended continued morning ventilation before children arrive and a follow-up check the following week.

That night Teacher Joy wrote to the parents' LINE group explaining everything the school had done: discarding flood-contaminated items, drying the walls before painting, choosing low-VOC products for the later work, and ozone treatment with before-and-after readings. Many parents replied with thanks. On reopening day, the children ran in to see the giraffe on the wall, and nobody asked about paint smell again.

Kindergarten flood-recovery checklist: before and after ozone

Before painting

• Have an electrician inspect wiring, low sockets within children's reach and all breakers before use.
• Wear rubber gloves, boots and a mask while removing mud, and keep children away from the area during clean-up.
• Discard cuddly toys, nap mattresses, books and absorbent toys that sat in floodwater, as they are hard to make safe.
• Wash hard plastic toys exposed to water with clean water and detergent, then disinfect according to the product label.
• Dry walls and floors quickly. Agencies such as the CDC advise cleaning and drying within 24 to 48 hours where possible to limit mold.

During painting and renovation

• Choose paints, varnishes and adhesives labelled low-VOC, and ask manufacturers for drying and curing times.
• Never paint over damp walls.
• Unwrap new furniture, cushions and toys in an open, well-ventilated area, not inside a closed classroom.
• Plan for painting and gluing to finish several days before reopening, leaving time for ventilation and ozone.

Treatment day

• Book a day with no children in the building, and empty the area of people, pets and plants.
• Remove food, milk and snacks from the rooms.
• Close doors and windows, post signs at every entrance, and brief security and cleaning staff.

After treatment and the first week back

• Re-enter only when the team confirms the rest and ventilation period is over.
• Disinfect tables, handles and high-touch surfaces according to the label, then set up rooms as normal.
• Open windows in the morning before children arrive, and keep an eye on rooms that were slow to dry.
• Tell parents what the school has done, and ask teachers to watch for symptoms. If a child has persistent symptoms, advise parents to see a doctor.

Frequently asked questions: ozone for kindergartens after repainting

1. Can we treat one wing while children are in another?

Not recommended. Treatment must be in an empty, closed space, and kindergartens should schedule it when no children are in the building at all, both to prevent a child wandering in and for parents' peace of mind.

2. When can children go back into the rooms?

According to the service information, the space is ready about two hours after treatment, and the team will tell you when it is safe to re-enter. Most schools treat on a weekend before reopening so teachers can set up the same day or the next.

3. Do toys and books need to come out?

Toys that touched floodwater must be washed or discarded first; ozone does not replace cleaning them. For clean, dry toys and books, the team will advise during the survey which items to remove, especially paper artwork you want to keep. All food must be taken out.

4. Does ozone mean we do not have to wait for paint to dry?

No. Paint and varnish must dry and cure as the manufacturer specifies. Ozone reduces lingering odours and volatile compounds; it does not make paint dry faster.

5. How should we explain this to parents?

Walk them through the steps: discarding contaminated items, cleaning, drying, choosing low-VOC materials, ozone treatment on a day with no children, and before-and-after TVOC readings. Honest, step-by-step communication builds more trust than a short reassurance.

6. Can a nursery or childcare centre inside a condo use the service?

Yes. According to the service information, WHD serves homes, condos, offices and many other building types. The team assesses the space and any building restrictions before planning.

Bright classrooms, fresh air, ready for the children

Talk to WHD about a school survey, TVOC measurement and ozone treatment on a weekend before reopening.

Book Classroom Ozone Before Reopening

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

Related services

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

References

• 2026 Bangkok floods (Wikipedia)
• Al Jazeera: Disaster zone declared across Bangkok as heavy rain triggers flooding
• CDC: Floods, cleanup guidance
• WHO fact sheets