A Story from the Field: Three Weeks Before Term for Director Prasert

Director Prasert runs an extended-opportunity school in Sena district, Phra Nakhon Si Ayutthaya, with several hundred students from primary level up to lower secondary. Three two-storey classroom buildings stand around a football field, a high-roofed canteen sits to one side, and the students' toilets are in a small separate building at the back of the school.

From late September into early October 2026, water from the river and local canals spilled into the school grounds. It flooded the ground floors of all three classroom buildings, the canteen and the toilet block. More than half a metre of water stayed for over two weeks. When it finally drained away, the scene was grim: students' desks and chairs toppled and caked in mud, whiteboards streaked with water marks, shelves in the ground-floor library collapsed with books stuck together in sodden lumps. The canteen floor was buried under thick mud, especially beneath the long dining tables. The food stalls' freezers and stoves had been underwater. The toilet block smelled so bad that teachers had to block the entrance.

With less than three weeks before semester 2 of the 2026 school year, teachers, caretakers and volunteer parents spent days shovelling mud and scrubbing. Even so, the ground-floor classrooms still smelled musty, and spots of mold were appearing on the walls. Several teachers started coughing and reacting to the dust. In the school's LINE group, parents asked whether the canteen would really be safe for their children to eat in. Director Prasert contacted World Health Disinfection (WHD) and asked for a plan that could be finished before opening day.

The Risks Schools Must Understand Before Reopening After a Flood

A school brings large numbers of people together in limited space: students, teachers, support staff and canteen vendors. If germs or mold remain, illness spreads many times faster than it would at home.

Ground-floor classrooms

Desks, chairs, shelves, equipment cupboards and floors were in direct contact with floodwater. Mud gets into desk grooves, chair legs and room corners. Damp plaster walls and ceiling boards become sources of mold that release spores into the air for the entire time students are sitting in class.

The canteen and food stalls

This is the highest-risk area for gastrointestinal illness. E. coli and other bacteria from sewage in the floodwater can remain on dining tables, benches, counters, dishes and cooking equipment. If cleaning is not thorough, many students could fall ill with diarrhea at the same time in the first week of term.

Student toilets

Drains and septic tanks are the route by which sewage flows back in, so toilets carry both germs and strong odors. They are also used by every student, every day.

Diseases to watch for

• Diarrhea and food poisoning from contamination in the canteen and toilets.
• Leptospirosis, a risk for caretakers, teachers and volunteers who wade through mud during the clean-up.
• Skin infections and infected wounds from contact with floodwater and mud.
• Allergies and asthma from mold spores in closed or air-conditioned classrooms.
• Dengue fever from Aedes mosquitoes breeding in standing water around the school.

Why the Timing of Semester 2 Makes This Urgent

In Thailand, the break between semesters is short, and semester 2 of the 2026 school year opens only a few weeks after the water has receded in many parts of Ayutthaya. That leaves schools with a narrow window in which to clean, repair, disinfect and ventilate every affected building, while teachers also need time to prepare lessons and catch up on a disrupted first semester.

The weather does not help. October and early November are still humid, and walls that sat in water for two weeks or more will stay damp for some time. Mold that is not dealt with in the first weeks after the flood will keep growing quietly behind cupboards and above ceiling boards, then appear in full view once classrooms are closed up and the air conditioning is switched on. By that point students are back, and treatment becomes much harder to schedule without disrupting lessons.

Acting during the break avoids that problem. Professional disinfection and ozone treatment can be completed while the buildings are empty, ventilation can run without affecting anyone, and the school can open its doors knowing that the hardest part of the recovery is already behind it.

Why a Big Wash Alone Is Not Enough

• Hosing down floors and desks. This removes mud but does not disinfect walls, ceilings, the undersides of desks or room corners.
• Pouring bleach in classrooms. The chlorine smell lingers for days, irritates students with allergies and corrodes steel desk and chair frames.
• Leaving the windows open. This helps drying but does not destroy mold spores or odors trapped in materials.
• Repainting to make things look clean. If walls are still damp and contaminated, the paint will bubble within a single semester.
• Limited manpower. Most schools have only a few caretakers. Thoroughly scrubbing every room in a few weeks is extremely difficult.

What a school needs is not more rounds of washing but a process that disinfects both surfaces and air thoroughly, works quickly over large areas, leaves no chemical smell in classrooms and produces clear evidence of the work, so that the director can answer questions from parents and the supervising education office with confidence.

The Solution: Building-by-Building Disinfection Fogging + Ozone Treatment, Finished Before Opening Day

WHD plans school projects by building and by risk. We start with the canteen and toilets, then move to ground-floor classrooms, the library and specialist rooms. Work is scheduled during the school break or at weekends so that it does not get in the way of teachers' preparation.

Chemgene HLD4H disinfection

Our disinfection service uses CHEMGENE HLD4H applied with ULV equipment that turns the disinfectant into an ultra-fine mist. It covers large classrooms, high-roofed canteens and multiple toilet rooms quickly. It leaves no harsh smell in classrooms and is not corrosive to desks, chairs, whiteboards or teaching equipment.

Ozone treatment for rooms that can be sealed

Our ozone treatment service suits air-conditioned classrooms, the library, computer rooms, the nurse's room and staff rooms, all of which can be closed tightly. Ozone helps destroy mold spores in curtains, books, cushions and carpets and breaks down musty odors, then decays back into oxygen. In open areas such as the canteen, fogging is the main treatment, with ozone used in kitchens or storerooms that can be closed.

Our process for schools

1. Survey and prioritisation. We walk the site with the director and the facilities teacher, identify buildings, rooms and risk points, and build a plan around the days remaining before term.
2. Preparation advice. We help teachers plan mud removal, main cleaning and the sorting of damaged books, teaching materials and equipment.
3. Canteen and toilets first. These are the highest-risk areas for gastrointestinal illness, so they are fogged first.
4. Classrooms and corridors. We move building by building, covering desks, chairs, walls and floors.
5. Ozone in sealable rooms. The library, computer room, nurse's room, air-conditioned classrooms and storerooms.
6. Ventilation, re-check and handover. Rooms are aired out, odors are re-checked, and we deliver a summary report with before-and-after photos that the school can share with parents and its supervising office.

10 Reasons Sena Schools Choose WHD Before Term Starts

1. Planned to finish before opening day. Work is divided by building and risk level.
2. Large areas covered fast. ULV disinfection fogging suits canteens and many classrooms.
3. No chemical smell left in classrooms. Chemgene HLD4H does not corrode desks or chairs.
4. Musty odors in closed rooms handled. Ozone treatment for libraries and air-conditioned classrooms.
5. The canteen gets priority. Reducing the risk of a diarrhea outbreak in the first week.
6. Toilets back in service. Germs and odors reduced where everyone needs to go.
7. A written summary report. For parents and the supervising education office.
8. Lighter load for caretakers. Teachers get more time to prepare lessons.
9. Dengue prevention. Mosquito spraying around buildings and playing fields.
10. Ongoing care for shared touchpoints. Use the Chemgene spray on door handles, stair rails and taps.

Before and After: Director Prasert's School

What Our Client Said

"We had very little time. The team helped us prioritise: the canteen and toilets first, then the classrooms. Everything was finished before term started. Once we posted the photos and the report in the parents' group, the safety questions dropped right away, and the teachers could finally breathe easily."
— Director Prasert (name changed), school director, Sena, Phra Nakhon Si Ayutthaya

School Checklist Before Semester 2/2026 Opens

• Have an electrician inspect ground-floor wiring, sockets, fans, air conditioners and distribution boards in every building.
• Check the drinking water system, filters and storage tanks, and clean them or replace filter cartridges.
• Ask canteen vendors to discard any ingredients that touched floodwater and to clean and disinfect their cooking equipment before reopening.
• Sort wet books, documents and teaching materials and record the damage.
• Clear drains and inspection pits around the buildings, and check the toilet block's septic tank.
• Remove standing water around the school to reduce Aedes mosquitoes before students return.
• Provide protective equipment for caretakers and volunteers, and watch for fever, calf pain or diarrhea.
• Tell parents the opening date, the recovery work already done and what students should bring.

An Example Two-Week Plan Before Term

• Days 1-3: Mud removal, main cleaning, sorting damaged items, clearing drains and a joint site survey with the WHD team.
• Days 4-5: Fogging the canteen, food stalls, kitchen and toilet block, with ozone in storerooms and kitchens that can be closed.
• Days 6-8: Fogging ground-floor classrooms building by building, including corridors and stairs.
• Days 9-10: Ozone treatment for the library, computer room, nurse's room and air-conditioned classrooms.
• Days 11-12: Ventilation, re-checks and mosquito spraying around the school.
• Days 13-14: Teachers set up classrooms, prepare materials and update parents with before-and-after photos.

The real plan is adjusted to the size of the school, the number of buildings and the extent of the damage. Our team will help you build a timetable that fits the days you have left before term.

Specialist Rooms That Need Extra Thought

• Library. Paper absorbs moisture and odor easily. Soaked books should be removed, while lightly damp books can be dried and the closed library treated with ozone to reduce spores and mustiness.
• Science laboratory. Check chemical cupboards for water damage and remove any containers that were submerged, following the school's chemical safety procedures, before disinfection begins.
• Computer room. Electrical equipment must be inspected by a technician. Fine-mist fogging and ozone allow the room to be treated without soaking keyboards and cables.
• Nurse's room. Beds, pillows and first-aid supplies at floor level should be replaced, and the room fully disinfected because sick students rest here.
• Music and sports storerooms. Mats, drums, balls and cushions trap moisture and smell. Ozone treatment in the closed storeroom helps, but badly soaked foam items are often better replaced.
• Teachers' rooms. Staff spend long hours here preparing lessons. Treating these rooms protects the health of the people who keep the school running.

Including these rooms in the plan from the start avoids last-minute surprises when teachers open a door a few days before term and find a smell nobody had noticed.

Keeping Parents and the Community Informed

Schools in Sena are at the centre of community life, and many families will have been affected by the same flood. Parents want to know that their children are returning to a safe environment, and clear communication goes a long way.

• Post a short update when the recovery plan is confirmed, including key dates.
• Explain in simple terms what disinfection fogging and ozone treatment do, and that all work takes place while students are away.
• Share before-and-after photos of the canteen, toilets and classrooms once each stage is complete.
• Remind families to keep children home and see a doctor if they develop a fever, diarrhea or a rash, and to inform the school.

When parents see a calm, organised recovery, they return their children with confidence, and the school can focus on what matters most: helping students catch up after a disrupted term.

Working with Canteen Vendors

In many Thai schools, the canteen is run by independent vendors rather than school staff. That makes coordination essential, because a single stall that reopens with contaminated equipment can undo all the work done elsewhere.

• Meet vendors early. Explain the recovery schedule and the date when the canteen will be fogged, so they can clear their stalls in advance.
• Agree what must be discarded. Any food, sauces, dry goods or ice that touched floodwater should be thrown away. Freezers and refrigerators that were submerged need inspection by a technician before use.
• Clean before disinfection. Grease and food residue reduce the effectiveness of any disinfectant, so vendors should wash pots, woks, cutting boards and counters thoroughly first.
• Rinse food-contact surfaces afterwards. After fogging and ventilation, vendors should rinse surfaces that touch food with clean water before preparing meals.
• Keep a simple routine. Daily wiping of tables and benches, regular cleaning of drains and proper waste disposal keep the canteen safe for the rest of the term.

Our team is happy to explain the process directly to vendors during the survey, so that everyone understands their role and the canteen opens on time.

Protecting Students' Health in the First Weeks Back

Even after a thorough recovery, the first few weeks of term deserve extra attention. Students are returning from homes that may also have been flooded, routines are disrupted and the weather is still humid. A few simple measures help the school stay healthy.

• Handwashing stations. Make sure soap and clean water are available at the canteen, toilets and classroom entrances, and remind students to wash before eating and after using the toilet.
• Daily ventilation. Open classroom windows in the morning, especially in rooms that were flooded, to help walls continue drying.
• Watch for returning mold. Ask teachers to report any new black spots or musty smells so they can be dealt with quickly.
• Monitor symptoms. The nurse's room should keep a simple record of students with fever, diarrhea or skin problems, so that any cluster can be spotted early.
• Mosquito control. Check for standing water in plant pots, gutters and discarded containers every week, and consider follow-up mosquito spraying if numbers rise.

These habits cost very little but protect the investment the school has made in recovery, and they reassure parents that their children's health remains a priority throughout the semester.

Frequently Asked Questions

Q1: Our school has several buildings. Must everything be done in one day?
A: No. We divide the work by building and risk level, starting with the canteen and toilets and then moving to classrooms and specialist rooms, so that everything is finished before term begins.

Q2: The canteen is open-sided. Can it be treated with ozone?
A: In open areas we rely mainly on disinfection fogging, because ozone disperses too easily. Kitchens, ingredient stores or stalls that can be closed are given additional ozone treatment.

Q3: Can moldy library books be saved?
A: Books that are soaked through should be removed. For books that are only slightly damp or musty, ozone treatment in a closed library helps reduce odor and mold spores, together with proper drying.

Q4: When can students go back into a room after ozone treatment?
A: Once ventilation has run for the time our team specifies, the ozone has turned back into oxygen. We recommend finishing all work at least one to two days before term starts.

Q5: Do you provide documents for budget claims or reports to the supervising office?
A: Yes. We issue quotations and provide a summary report with before-and-after photos that can support your reporting.

Q6: Which areas do you serve?
A: We serve Sena, Bang Ban, Phak Hai, Bang Sai, Lat Bua Luang and nearby areas of Phra Nakhon Si Ayutthaya. Contact us by phone or LINE to check availability.

Q7: Only part of our school flooded. Is it worth treating the dry buildings too?
A: Usually not in full. We focus on the buildings and rooms that were underwater, plus connected corridors, stairs and any rooms where people tracked mud during the clean-up. If the dry buildings show no musty smell or mold, normal cleaning is enough, and your budget goes where the real risk is.

Open the New Term with Confidence: Clean, Safe Rooms for Every Student

Book a school survey and plan your recovery in time for semester 2/2026 with the WHD team today.

See Our Disinfection Service – Click Here

Book Ozone Treatment – Click Here

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

Related Links

• Ozone treatment for odors and chemical residue
• Master Ozone Generator
• Mosquito spraying service
• All articles

External sources: World Health Organization – Floods and Department of Disease Control, Thailand