A Story From the Field: Two Weeks Before Term Starts

Dr. Chamaiporn looks after buildings and facilities for a university campus in Nong Suea district, Pathum Thani. The campus sits among irrigation canals and open rice fields, which is part of its charm on a clear morning and part of its vulnerability in a wet year. In early October 2026, after days of heavy, unrelenting rain, the canals could no longer carry the water away. It spilled over the banks and spread across the campus grounds. Two general lecture buildings and the ground floor of the science laboratory building stood in knee-deep water for the better part of a week.

On the morning the water finally drained away, Dr. Chamaiporn unlocked the doors of a two-hundred-seat lecture theatre. The first thing that met her was the smell: a heavy, sour mixture of damp and mud that hit her in the face and made her step back into the corridor. The front rows of lecture chairs had dried mud caked beneath the seats. A long, uneven tide line ran along the lower walls. The carpet down the central aisle was soaked through and had already started to show small white patches of mold.

Downstairs, the chemistry teaching lab was worse. The plywood storage cabinets under the benches had swollen and split at the edges. Several ceiling tiles showed dark, blotchy stains. The sinks were full of silt, and the drains were blocked solid. The fume cupboard looked fine at a glance, but there was a faint musty odor around its base where water had sat against the cabinet below.

The academic calendar on her office wall said the new semester would start in two weeks. Several thousand students would be walking back into these rooms at the same time. In the faculty LINE groups the questions had already started. "Are the classrooms safe yet?" "My daughter has asthma. Should she sit in a room that was flooded?" "Will the lab practicals still run on schedule?" Dr. Chamaiporn knew that hosing out the mud and switching on a few fans was not going to be enough. She needed a clear, defensible process for disinfection and mold control, something she could explain to university management, to lecturers, and to worried parents with a straight face.

Her situation is not unusual. Across Pathum Thani and the wider central region, schools, colleges and universities are facing the same race against the calendar this October. This article explains what is really going on inside a flooded teaching building, why the usual quick fixes fall short, and how a structured disinfection fogging and ozone treatment plan can get lecture halls and labs ready in time.

The Hidden Problems Inside a Teaching Building After the Water Recedes

Health risks. Floodwater that has flowed through canals, farmland and storm drains carries a wide range of microorganisms. Bacteria such as E. coli and the organisms that cause leptospirosis can be deposited on floors, chair legs, desk frames and anywhere mud has settled. These germs do not disappear just because the floor looks dry. They sit in corners, in the grooves of floor tiles, in the fabric of upholstered seats and in the gap between a cabinet and the wall.

At the same time, the humidity inside a closed building after a flood is extremely high. That is perfect for mold. Within days, mold starts to grow on painted walls, ceiling boards, carpet, plywood and fabric. As it grows, it releases spores into the air. For many people those spores are a trigger for allergies: sneezing, a blocked nose, itchy eyes and coughing. For students with asthma, they can provoke a genuine attack. Think about a typical lecture: three or four hours in a closed, air-conditioned room, breathing the same recirculated air. If that room still has active mold in its carpet and ceiling, the exposure is continuous.

Teaching and research risks. Laboratories need a higher level of cleanliness than ordinary classrooms. Residual bacteria and mold can contaminate experiments, especially in microbiology, food science and biotechnology teaching labs, where a stray spore can ruin a culture plate and an entire practical session. If lab sessions have to be postponed, the knock-on effect runs through the whole semester timetable, affecting lecturers, teaching assistants and students who need those practical hours to complete their courses.

Budget risks. Carpet, ceiling tiles, plywood cabinets and upholstered lecture seats that are left to develop mold may eventually need complete replacement. That is far more expensive than dealing with the problem early, when targeted cleaning, disinfection and ozone treatment can still save many of those materials.

Reputation risks. One photo of black mold on a classroom wall, posted on social media by a student, can quickly turn into questions directed at the whole university. Parents who are deciding where to send their children notice these things. A visible, well-communicated recovery plan does a lot to protect trust.

Time pressure. The period before the semester opens is short, and facilities teams are rarely large. The same few cleaners and technicians are responsible for multiple buildings at once. A clear, efficient process, with the right specialist support, is what makes the difference between opening on time and opening late.

Why Washing the Floor and Running Fans Is Not Enough

Relying on bleach alone. Household bleach works reasonably well on smooth, hard surfaces like tiles and laminate. It does not soak deep into carpet, ceiling boards or plywood, which is exactly where mold roots itself. The strong chlorine smell in a closed lecture hall can sting the eyes and nose, and mixing bleach with other cleaning products can release dangerous gases. In a laboratory, where many different chemicals are stored, that risk is even more serious.

Drying with fans. Fans reduce surface moisture, but they also blow mold spores around the room and into the air-conditioning system. Instead of removing the problem, they can spread it to rooms that were never flooded.

Air fresheners and deodorizers. These only mask the smell for a while. They do nothing to the mold and bacteria that are producing the odor. Within a day, the musty smell returns, often mixed with an artificial floral scent that many students find even more unpleasant.

Painting over the stains. Repainting a damp, moldy wall is one of the most common and expensive mistakes after a flood. The mold continues to grow under the new paint, pushing it off in bubbles and blisters and producing new black spots within a few months. The building then has to be repainted again, and this time the mold problem is bigger.

None of these steps is useless on its own. Cleaning, drying and eventually repainting are all part of recovery. The point is that they need to be done in the right order, with proper disinfection and mold treatment in the middle.

The Solution: Chemgene HLD4H Disinfection Fogging Combined With Ozone Treatment

World Health Disinfection provides a professional disinfection fogging service using Chemgene HLD4H disinfectant. The solution is applied with ULV (ultra-low volume) equipment that breaks it into a very fine mist. That mist drifts under lecture chairs, between lab benches, into corners and onto surfaces that a cloth or mop simply cannot reach. Chemgene HLD4H does not leave behind a harsh, lingering chemical smell, which matters in rooms that students will be sitting in for hours at a time.

The second stage is our ozone treatment service. Ozone is a gas, so it penetrates materials that a liquid cannot fully reach: carpet fibers, the foam inside seat cushions, porous ceiling boards and the air ducts of the room. Ozone acts on mold spores and bacteria and breaks down the odor molecules that create that heavy, musty smell, rather than covering it up.

Our Step-by-Step Process for Lecture Buildings and Laboratories

1. Site survey. Our team walks the buildings with your facilities staff. We record which rooms were flooded, how high the water reached, current moisture levels, visible mold, and materials that are likely beyond saving.
2. Mud and clean-up guidance. We advise on what to remove and clean first: carpet that sat underwater for days, collapsed ceiling tiles, soaked paper archives and swollen particleboard. Getting the heavy mud out first allows the disinfectant to reach the actual surfaces.
3. Laboratory preparation. We ask laboratory staff to store chemicals in closed cabinets or move them out, shut off gas and any unnecessary power, and cover or remove scientific instruments, computers and other sensitive electronics.
4. Disinfection fogging. We fog Chemgene HLD4H throughout each room, covering desks, chairs, benches, handrails, door handles, sinks and floors.
5. Ozone shock treatment. We seal the room and run ozone at a controlled dose matched to the room volume. No people, animals or plants may be inside during treatment.
6. Ventilation. After the treatment period, doors and windows are opened and fans or extraction systems are used to clear the air. Staff only re-enter once the ozone has broken down.
7. Re-check. We inspect odor and visible mold together with your team. Where walls are still very wet, we recommend a follow-up plan once they have dried properly.

Safety note on ozone: Ozone is highly effective at disinfection, which is exactly why it must be used carefully. No people, pets or plants can remain in the room during treatment, and the space must be fully ventilated before anyone goes back in. Rubber parts and sensitive electronics, artworks or precision instruments should be covered or removed. Our technicians always control the ozone dose according to the size and condition of the room.

Areas That Need Special Attention on a University Campus

Large lecture halls. These rooms usually have hundreds of upholstered seats, wall-to-wall carpet and high ceilings. Foam padding in the seats acts like a sponge for floodwater and becomes a major source of musty odor. Ozone can reach into the foam, but where seats were submerged for a long time, replacing the cushions may also be the sensible choice. We will tell you honestly which is which.

Science laboratories. Lab benches, sinks, under-bench cabinets and fume cupboards have many joints, gaps and crevices. ULV fogging allows the disinfectant to reach these awkward places. High-precision instruments such as balances, spectrophotometers and microscopes should be checked separately by the lab manager according to the manufacturer's instructions, and kept out of the room or securely covered during treatment.

Computer rooms. Before any equipment is switched on, an electrician should check that the wiring, sockets and distribution boards are dry and safe. Computers and network equipment should be covered or moved out before ozone treatment.

Air-conditioning systems. Classroom air-conditioners that ran in humid conditions, or that were simply switched off in a flooded room, often have mold in their filters, coils and drain pans. The right order is to clean the air-conditioning units first, then fog, then run ozone treatment so the gas can also pass through the ducts and vents.

Toilets, corridors, stairwells and lifts. These are shared touchpoints for thousands of students. They should be fogged on the same day as the classrooms so the whole building is ready together, rather than students walking through an untreated corridor into a treated room.

Libraries and archive rooms. Books and paper records that were wet need separate handling, but rooms that were damp without being submerged can benefit greatly from ozone treatment to stop mold growth and remove the musty smell that clings to paper.

10 Reasons Universities Choose Disinfection Fogging and Ozone Treatment Before the Semester

1. Reduce the risk from floodwater germs with a disinfection service that covers the whole building, not just the visible floor.
2. Deal with mold spores in carpet, ceilings and seat cushions through ozone treatment.
3. Lower the chance of allergy and asthma symptoms among students who sit in closed rooms for hours.
4. Use Chemgene HLD4H, which leaves no harsh chemical smell in rooms that must be used straight away.
5. Keep laboratory practicals on schedule and avoid a chain of postponed sessions.
6. Work building by building or floor by floor, matching the plan to the time left before term.
7. Save money by stopping mold before it forces you to replace carpets, ceilings and furniture.
8. Have a clear, documented process to share with management, lecturers, students and parents.
9. Repaint and repair with confidence once the mold has been treated and the walls are dry.
10. Add a mosquito spraying service around buildings while standing water remains on campus.

Before and After Recovery

A Word From a Facilities Manager

"What helped us most was the sequencing. The team told us clearly which rooms needed the air-conditioners cleaned first, which labs had to have chemicals moved out, and which rooms had to wait for the walls to dry. Once everything was done, we wrote up the steps for the faculty and posted them in the student groups. The worry in those groups dropped a lot."
— Facilities manager at a campus in Nong Suea district (a representative field scenario)

A Practical Two-Week Plan Before the Semester Opens

Every campus is different, but the following outline works well for most teaching buildings that were flooded at ground level. Adjust it to the time you actually have.

• Week one after the water recedes. Remove mud and silt. Pull out carpets, ceiling tiles and cabinets that are clearly beyond saving. Ask an electrician to inspect wiring and distribution boards before power is restored to flooded rooms. Clean the air-conditioning units. Open windows and doors whenever the weather allows to start drying the structure.
• Start of week two. Fog and ozone-treat lecture halls, laboratories, toilets and corridors in order of priority. Rooms needed for the first week of teaching go first.
• End of week two. Re-inspect. Repaint only walls that are fully dry. Return desks and chairs to position. Announce to students and staff that the building is ready, with a short summary of what was done.
• After term begins. Keep an eye on spots that were very damp. If new mold appears, contact us so we can plan a follow-up treatment before it spreads.

A health reminder for students and staff: anyone who waded through floodwater in recent weeks and then develops a sudden high fever, headache or muscle pain, especially in the calves, should see a doctor promptly and mention the flood exposure. These can be early signs of leptospirosis, which is treatable when caught early. Further guidance is available from the Department of Disease Control and the Department of Health.

How to Communicate the Recovery to Students and Parents

Doing the work is only half of the job. The other half is telling people about it in a way that builds trust. Universities that handle this well tend to follow a few simple principles.

Be specific. Instead of "the building has been cleaned," say which buildings and floors were treated, on which dates, and what the process involved: mud removal, air-conditioner cleaning, disinfection fogging with Chemgene HLD4H, ozone treatment and ventilation.

Be honest about what is still in progress. If a few rooms are waiting for walls to dry before repainting, say so and explain that they will not be used until they are ready. People trust a plan that admits its limits.

Give a contact point. Let students know who to tell if they notice a musty smell or a new mold spot. Early reports make follow-up treatment quicker and cheaper.

Remind people about personal health. A short note about leptospirosis symptoms, hand washing and avoiding standing water shows that the university is thinking about students as people, not just about its buildings.

Frequently Asked Questions

Q: How long does it take to treat a large lecture hall?
A: It depends on the room size, the number of seats and how damp the room still is. Our team assesses each room on site and gives you a schedule before work starts, including ventilation time.

Q: Do all laboratory chemicals have to be removed?
A: They should be stored in closed cabinets or moved out, following your lab manager's guidance, so they are not directly exposed to the disinfectant mist or to ozone.

Q: Will ozone damage computers or scientific instruments?
A: We use a controlled ozone dose, and we always recommend covering or removing electronics, rubber components and delicate instruments before treatment.

Q: Can you treat only some floors or rooms?
A: Yes. Many campuses start with flooded ground floors or the rooms needed first in the timetable, then treat other areas in a second phase.

Q: When can people go back into the room after ozone treatment?
A: Only after the room has been ventilated and the ozone has broken down. Our technicians will tell you when it is safe for staff and students to re-enter.

Q: Which areas do you cover?
A: Nong Suea, Thanyaburi, Khlong Luang, Lam Luk Ka, Mueang Pathum Thani and nearby districts, as well as educational institutions in other flood-affected provinces.

Get Your Teaching Buildings Ready Before the First Lecture

Talk to the World Health Disinfection team about a disinfection fogging and ozone treatment plan for your lecture halls, laboratories and campus buildings in Nong Suea and across Pathum Thani.

See Our 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 and health and the Department of Disease Control, Ministry of Public Health.