A Story From the Field: The Morning the Last Family Went Home

It is a Sunday morning in mid-October 2026. Mr. Wichai, the teacher in charge of the sports hall at a school in Bang Sai District, Phra Nakhon Si Ayutthaya, watches the last evacuee family load their sleeping mats, bags of clothes and a rice cooker onto a pickup truck. For almost three weeks, his gym has served as a temporary shelter for families from the villages along the Chao Phraya River. The water is finally going down, and everyone is relieved to be heading home. For Mr. Wichai, however, the hardest part of the job is only just beginning.

When he walks to the middle of the court, the first thing that hits him is the smell. It is a heavy mix of sweat, cooked food, blankets that never quite dried, and the stale odor drifting from restrooms that served hundreds of people a day. A long trail of dried mud runs across the rubber floor from the back door, the entrance people used while wading in from the flooded road. In the equipment store, black spots have started to bloom on the walls and on the gymnastics mats. In the corner that volunteers turned into a first-aid room, where elderly evacuees with diarrhea and fever were looked after, two bins of medical waste are still waiting to be collected.

The principal has already called twice. The second semester starts in less than three weeks. More than five hundred students will be back in this building every day for physical education, morning assembly and school events. Mr. Wichai keeps coming back to one question he cannot answer: "If we just wash the floor, is that enough? Have the floodwater germs and the bugs from all those sick people really gone?"

This is not only Mr. Wichai's problem. Temples, community halls, sub-district (TAO) meeting halls and school gyms across Bang Sai, Bang Ban, Sena and Phak Hai all opened their doors as evacuation centers during this year's floods. Now every one of them faces the same challenge: how do you hand a building back to the community in a condition that is genuinely safe, not just visibly tidy?

Why Post-Flood Shelters Carry More Risk Than You Might Expect

A temporary shelter is, by definition, a crowded place where many people live together for an extended period. Babies, older people, bedridden patients and residents who have just waded through floodwater all share the same floor, the same restrooms and the same air. Put those factors together and you have conditions in which germs can build up on surfaces and in the air far faster than in an ordinary building. When the evacuees leave, those germs do not leave with them.

1. Floodwater germs carried in on shoes and clothing

Floodwater in the low-lying Chao Phraya basin is frequently contaminated with sewage, animal urine and waste. Bacteria such as E. coli, and Leptospira, the organism that causes leptospirosis (often called "rat fever" in Thailand), can survive in the mud that dries onto court floors, doorframes and stair edges. When students later sit on the floor for stretching, or grab balls and equipment that were stored nearby, the risk is passed straight on to them. Children are especially vulnerable because they touch everything and then touch their faces.

2. Stomach bugs and respiratory infections that circulate in shelters

Diarrhea, colds and flu, conjunctivitis and skin infections are all common in evacuation centers, simply because people share restrooms, utensils and sleeping space. Many viruses and bacteria can survive on hard surfaces such as door handles, stair rails, taps and folding tables for days. Without a proper disinfection step, whoever uses the building next inherits that risk. A first-aid corner that treated sick evacuees deserves particular attention, because that is where contamination is likely to be heaviest.

3. Mold and airborne spores

Most gyms are open, high-roofed buildings, and you might expect them to dry quickly. During a flood, though, outdoor humidity is extremely high. Mats, blankets and mattresses stacked on the floor trap moisture underneath them for days at a time. Mold then spreads across storeroom walls, gym mats, stage curtains and ceiling boards. Mold releases microscopic spores into the air, and those spores are a well-known trigger for allergies, asthma attacks and persistent coughs, again with children being among the most sensitive.

4. Cost, reputation and a ticking clock

If a group of students falls ill shortly after the new term begins, parents will immediately ask questions of the school and of whichever agency managed the shelter. Closing the building again for a second, more thorough clean wastes teaching time and budget. Gym mats and soft equipment that go moldy have to be thrown away and replaced. Getting the job right before the building is formally handed back is far more cost-effective than fixing problems after complaints begin.

Common Fixes That Usually Fall Short

Facility managers do their best with the tools they have. Unfortunately, the most common approaches tend to deal with what you can see, rather than what you cannot.

Pouring bleach and scrubbing the floor. Diluted bleach can be useful on surfaces that have already been cleaned of visible dirt. Mixed too strong, however, it produces harsh fumes that irritate the lungs, and it can damage rubber sports flooring and varnished timber courts. More importantly, a mop or a scrubbing brush never reaches the high walls, ventilation openings, the underside of bleachers or the back corners of storerooms, which are exactly the places where spores and dust collect.

Opening the doors and running fans. Ventilation is good and necessary. But moving air only removes some of the moisture. It does not kill bacteria, viruses or mold spores, and in some cases strong fans actually stir up spores and spread them more widely through the building.

Air fresheners and incense. A pleasant scent can mask a musty smell for a few hours. The odor molecules embedded in mats, curtains, foam and other porous materials are still there. As soon as the humidity rises again, the bad smell comes right back.

Painting over moldy walls. A new coat of paint makes a wall look clean, but the mold underneath the paint is still alive. Within a few months it pushes through as bubbles, peeling patches or fresh black spots, and you have paid for the paint job twice.

The weakness shared by all of these methods is that none of them systematically deal with the invisible germs suspended in the air and hidden in the corners of a large building. A shelter needs a process designed for its scale.

Why Bang Sai's Setting Makes Handover Hygiene Even More Important

Bang Sai sits on a broad, flat stretch of the Chao Phraya floodplain, surrounded by rice fields, canals and riverside villages. When the river rises, water does not simply pass through and drain away. It spreads slowly across fields and lanes, lingers in low spots for weeks, and picks up whatever it touches along the way: septic tank overflow, livestock waste, fertilizer and household rubbish. By the time evacuees reach a shelter, many of them have walked through this water for long distances, often in sandals or barefoot.

The district is also home to many older residents and multi-generation households. Shelters here typically host a higher share of elderly people, people with chronic illnesses such as diabetes or high blood pressure, and young grandchildren cared for by grandparents. These are precisely the groups most at risk from infections and from the respiratory effects of mold. A shelter that cared for them deserves a careful clean-up afterwards.

Finally, school gyms and temple halls in rural Ayutthaya are true community hubs. The same hall that housed evacuees will soon host morning assemblies, sports days, merit-making ceremonies, village meetings and perhaps a health screening day run by the local health-promoting hospital. Hundreds of people from different households will pass through within weeks. That makes the handover moment the single best opportunity to reset the building's hygiene for everyone who will use it next.

Seen this way, disinfection fogging and ozone treatment are not a luxury. They are a sensible, one-time investment that protects the whole community and lets the building go back to its normal role with a clean slate, and with a clear record of what was done.

The Solution: Chemgene HLD4H Disinfection Fogging Plus Ozone Treatment by World Health Disinfection

World Health Disinfection (WHD) has designed its post-flood recovery service for large spaces such as shelters, gyms, assembly halls and multi-purpose pavilions. It combines two technologies that complement each other.

1. Professional disinfection fogging with Chemgene HLD4H. The team uses ULV (ultra-low-volume) foggers that turn the disinfectant into an extremely fine mist. Because the droplets are so small, they stay airborne long enough to drift up to high walls, under the bleachers, into ventilation gaps, storerooms and restrooms, coating surfaces far more evenly than hand wiping ever could. Chemgene HLD4H is a disinfectant used in medical and healthcare settings. It is effective against bacteria, viruses and fungi, and it does not have the sharp chlorine smell that makes people reluctant to re-enter a freshly cleaned room.

2. Ozone shock treatment. Once the fogging is complete, the building is sealed and ozone gas is released at a concentration calculated for the volume of the space. Ozone is a gas, so it penetrates places liquids cannot: into foam mats, curtains, upholstery and every cubic meter of air in the hall. It helps destroy mold spores and breaks down the molecules that cause musty smells, body odor, food smells and drain odors, rather than simply covering them up.

Why use both? Fogging deposits a disinfectant film on hard surfaces, where people actually touch, while ozone reaches into soft, porous materials and the air itself, where liquids cannot go. Used together in the right order, they cover the two main ways germs, spores and odors linger in a large hall after it has housed many people. Neither step replaces basic cleaning, which is why the team always starts by advising on mud and waste removal.

Step-by-step service for shelters and gyms

1. Site survey: The team inspects the building size and roof height, the flood line, visible mold, restrooms, the temporary first-aid area and waste collection points, and plans the amount of disinfectant and the ozone exposure time accordingly.
2. Clean-up guidance: Staff advise on removing mud, rubbish and damaged mattresses and mats, separating medical waste from the first-aid area, and washing off heavy dirt first. Disinfectants work best on surfaces that are free of thick soil.
3. ULV disinfection fogging: Chemgene HLD4H is fogged throughout the building, with particular attention to high-touch points such as door handles, railings, taps, bleachers, folding tables and restroom floors.
4. Ozone shock treatment: Doors and windows are closed, ozone generators are positioned at calculated points, and the building is treated for the time appropriate to its volume, with no people, pets or plants inside.
5. Ventilation: When treatment is complete, the team opens doors and windows and runs fans so that the ozone breaks down back into oxygen before anyone is allowed back in.
6. Re-check and handover: The team inspects odor levels and general condition together with the building manager, and gives advice on follow-up care such as daily ventilation and watching for damp spots.

10 Reasons Bang Sai Shelters and Gyms Should Be Disinfected and Ozone-Treated Before Handover

1. Reduce risk from floodwater pathogens such as E. coli and the bacteria behind leptospirosis with a professional disinfection service.
2. Break the chain of stomach bugs, colds and skin infections that may linger after weeks of crowded living.
3. ULV mist reaches high walls, the underside of bleachers and corners that ordinary wiping cannot.
4. Use Chemgene HLD4H, a disinfectant used in healthcare, with no harsh smell and gentle on sports floors and equipment.
5. Ozone treatment tackles mold spores in mats, stage curtains and porous materials that cannot be washed.
6. Break down stale, sweaty and food odors embedded in the building instead of masking them.
7. Help the school reopen on schedule, without closing the hall again because of smells or mold.
8. Lower the risk of allergies and asthma for children who use the gym every day.
9. Give parents and the wider community confidence that the space has been looked after properly.
10. Get ongoing advice, and add a mosquito spraying service around the building while standing water remains.

Before and After

What Facility Managers Tell Us

"At first I thought washing the floor and leaving the doors open would be enough, but the smell just would not go away, especially in the mat store. After the team fogged and ozone-treated the hall, the difference when you walked in was obvious. Just as important, we could tell parents exactly what had been done instead of just saying we had cleaned."
— Building manager, school gym in Bang Sai District (a representative scenario from the field)

How to Prepare the Building Before the Team Arrives

A little preparation helps the fogging and ozone treatment achieve their full effect. Here is a practical checklist for shelter and gym managers:

• Remove mats, blankets and mattresses left behind by evacuees, separating items that can be saved from those that must be discarded.
• Collect general rubbish and medical waste from the temporary first-aid area, bag them separately and coordinate with the local authority for proper disposal.
• Sweep and rinse thick mud from floors and walkways, always wearing rubber boots and gloves.
• Unplug electrical equipment such as sound systems and floor fans, and lift valuables off the floor.
• Move potted plants and aquariums out of the building before ozone day.
• Inform caretakers and other staff of the period when entry is not permitted.

If certain rooms were used as sleeping areas for elderly people or small children, let the team know, so they can give extra attention to floors, lower walls and furniture in those rooms. For gymnastics mats, yoga mats and fabric items you want to keep, consider adding our dust mite removal service.

It is also worth thinking about what happens after handover. Keep doors and high windows open for a few hours each morning during the first weeks, check the storeroom and under the stage for new damp patches, and make sure gutters and drains around the building are clear so that the next heavy rain does not push water back inside. These simple habits help the results of the treatment last.

Frequently Asked Questions

Q: Can a large gym with a high roof really be disinfected thoroughly?
A: Yes. ULV foggers create very fine droplets that stay suspended in the air for a long time, so they spread to high areas and corners much better than spraying or wiping. The team calculates the building volume and plans fogging positions to suit.

Q: How long before we can use the building again?
A: After fogging, you generally wait for the mist to settle and surfaces to dry. After ozone treatment, the space must be ventilated so the ozone can break down first. Timing depends on the size of the building, and the team will confirm when it is safe on the day of service.

Q: Is Chemgene HLD4H safe on rubber and wooden sports floors?
A: Chemgene HLD4H does not rely on corrosive levels of chlorine or alcohol, so it suits a wide range of surfaces. The team still checks any special materials before fogging.

Q: What should we do with the school's plants and animals during ozone treatment?
A: Take them all out of the treatment area, including aquariums and animal cages. High concentrations of ozone are harmful to living things. They can be returned after the space has been ventilated.

Q: Can temple halls and TAO meeting halls used as evacuation centers book this service?
A: Absolutely. The service is suitable for any public building that hosted evacuees, including temples, community halls, assembly halls and multi-purpose buildings in Bang Sai and neighboring districts.

Q: Is one treatment enough?
A: For handing a building back after the water recedes, one correctly performed round of fogging plus ozone treatment is usually sufficient. If the building still has leaks or persistently high humidity, fix the cause first and consider a follow-up check.

Q: How far in advance should we book?
A: Demand is very high after floods. Contact the team as soon as you know your handover date so a survey and service slot can be arranged before the new term starts.

Hand Your Shelter Back Clean, Safe and Ready

Talk to the World Health Disinfection team today to plan disinfection fogging and ozone treatment for gyms, evacuation centers and public buildings in Bang Sai, Phra Nakhon Si Ayutthaya.

View Disinfection Service – Click Here

Book Ozone Treatment – Click Here

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

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References: WHO – Floods fact sheet and the Department of Disease Control, Thailand Ministry of Public Health.