A typical scenario: the smell in the ground-floor records room

(An illustrative example case, not a real person.)

Nid works in the administrative office of a faculty at a university in the Bang Kapi area. When the water went down, she was the first to go back into the ground-floor records room. Files on the lowest shelves had swollen, cardboard boxes had slumped into leaning towers, and a long brown stain ran across the walls at the height the water had reached. She opened every window, switched on the fans and assumed that a few days of airing would be enough.

Less than a week later, the file spines were dotted with grey-green and black powdery specks, and moving a box raised a faint haze. A colleague with asthma coughed whenever he entered, Nid sneezed all afternoon, and the musty smell followed her home. Which documents should be kept, and how would anyone know when the room was safe to work in all day again?

Grey-green powder like that is often a sign of one of the most common mold groups in damp buildings, and Aspergillus is one of them.

The Ramkhamhaeng University flood of 2026, as reported

The facts in this section come only from Thai PBS reporting on the 2026 flood at Ramkhamhaeng University. We do not add numbers or details that are not in that report.

• Period: the campus flooded from 25 September to 1 October 2026, roughly six days.
• Depth: close to 2 metres at some points.
• Buildings affected: more than half of the university's 65 buildings, including the Computer Institute, the Faculty of Education, the Central Library, the demonstration school, the sports centre and the medical service unit.
• Damage: estimated at more than 200 million baht, described as the worst in about four decades.
• University decision: it chose not to pump water out into the surrounding community.
• Academic calendar: classes resume on 5 October 2026, and final exams run from 14 to 28 October as originally scheduled.

These facts matter directly for mold risk. Water standing in buildings for about six days means that paper, plywood, ceiling boards, gypsum walls and carpets were soaked far longer than the 24 to 48 hours within which public health agencies such as the CDC advise cleaning and drying to limit mold. A building like the Central Library holds large amounts of books and paper, which are ideal food for mold. A medical service unit is a place where people with weakened immune systems may come for care. And when tens of thousands of students return for classes and exams within a few weeks, indoor air quality is no longer a minor issue.

What is Aspergillus?

Aspergillus is a genus of filamentous mold found all over the world. There are several hundred species, but the ones most often linked to human health are Aspergillus fumigatus, Aspergillus flavus and Aspergillus niger. These molds live in soil, decaying leaves, compost, stored grain and indoor dust, where they break down organic matter. Most people breathe in Aspergillus spores every day without any symptoms, because the immune defences in healthy lungs clear them.

What makes Aspergillus medically important is the size of its spores: roughly 2 to 3 micrometres, small enough to stay airborne for a long time and to travel deep into the air sacs of the lungs. A. fumigatus also grows well at human body temperature and above, which most molds cannot do. When these molds find wet material containing organic matter, they produce masses of threads and spore heads, which look like powder or soft fuzz in grey-green, yellow-green or black, depending on the species.

Aspergillus disease does not spread from person to person; people become ill by breathing in spores from the environment. Reducing indoor spores is therefore the core of prevention, which is why the CDC flags heavy post-flood mold growth as a fungal illness concern.

How floods make Aspergillus multiply indoors

Mold needs three things to grow: moisture, food and a suitable temperature. Bangkok buildings at the end of the rainy season are already warm. A flood supplies the other two in one go. Water does not simply wet the floor; it wicks up into absorbent materials such as paper, wood, fabric and gypsum board, all of which contain cellulose that mold can eat. When the water also carries silt and organic debris that coat every surface, the mold gets even more food.

After the water recedes, humidity in a closed building often stays high for days, especially without power or air conditioning. Spores already in ordinary dust can germinate within one to two days, and growth is often clearly visible within one to two weeks.

The moment when airborne spore levels peak is often not while the building is underwater, but when everyone goes back in to clean. Pulling down ceiling boards, lifting boxes of files, ripping up carpet, dry sweeping and scrubbing walls all release huge numbers of spores into the air at once. That is why every post-flood safety guide stresses particle-filtering masks and keeping high-risk people away during clean-up.

Where Aspergillus hides in a university building after a flood

University buildings contain a wider range of materials and spaces than a typical home. These are the places that need careful inspection:

• Libraries and records rooms: soaked books, journals, files and cardboard boxes are dense sources of cellulose. Mold grows on spines, between pages and under shelving.
• Gypsum and acoustic ceiling tiles: even if water never reached the ceiling, moisture rising and collecting above the tiles is enough to support growth, especially in rooms closed for days.
• Partition walls and wall cavities: the inside of a wall dries slowly, so mold can grow unseen until a musty smell leaks out through sockets and joints.
• Air conditioning and ductwork: filters, drain pans, cooling coils and duct insulation that got wet can spread spores throughout a building if the system is switched on before it is inspected and cleaned.
• Carpets, upholstered chairs, curtains and felt notice boards: fibrous materials hold a lot of water and are very hard to dry all the way through.
• Computer rooms, the sports centre and the demonstration school: dust in equipment, gym mats, foam equipment and stuffy storerooms.
• Clinic and medical service areas: they need the highest standard because some users have weakened immunity.

Warning signs include an earthy or old-paper smell, powdery patches, bubbling paint, ring stains on ceilings, and sneezing or coughing that worsens only in that room.

Aspergillus symptoms, illnesses and who is most at risk

Illness caused by Aspergillus is called aspergillosis, and it takes several forms. Severity depends more on the health of the person exposed than on the mold itself. The information below is general knowledge to help you notice symptoms; it is not a diagnosis.

• General allergy and irritation: blocked or runny nose, sneezing, itchy eyes, cough and throat irritation, which can occur in anyone exposed to a lot of moldy dust.
• Asthma flare-ups: people with asthma or chronic lung disease may experience breathlessness, chest tightness and wheezing.
• Allergic bronchopulmonary aspergillosis (ABPA): seen in some people with asthma or cystic fibrosis; it makes asthma harder to control and can cause coughing up thick plugs of mucus.
• Fungal sinusitis: chronic nasal congestion and a dull ache around the face.
• Aspergilloma and chronic pulmonary aspergillosis: usually in people who already have cavities or scarring in the lungs, for example after pulmonary tuberculosis. Symptoms can include a long-lasting cough, weight loss, tiredness or coughing up blood.
• Invasive aspergillosis: the most serious form, occurring in people with severely weakened immunity. The infection can spread from the lungs to other organs and needs prompt medical care.

People who need extra caution and should not clean moldy areas themselves include those receiving chemotherapy or with low white blood cell counts, organ or bone marrow transplant recipients, people on high-dose steroids or long-term immunosuppressive drugs, people living with HIV whose immunity is low, people with asthma, COPD or a history of pulmonary tuberculosis, older adults, babies and young children, and pregnant women, who should avoid unnecessary exposure to dust and chemicals.

Important: if, after returning to a building, you develop a fever, a cough that will not go away, breathlessness, blood in your cough, or asthma that your usual medicine cannot control, see a doctor and mention that you have recently been exposed to a flooded area and mold. This is especially important for people with chronic illness or weakened immunity. If you waded through floodwater and then developed fever and calf pain, tell the doctor, as this may be leptospirosis. This article is not medical advice and does not replace examination or treatment.

What happens if indoor mold is left to grow

Health: students and staff spend hours a day in classrooms, exam halls and libraries. Spore-laden air keeps allergy and asthma sufferers symptomatic all day and raises the risk for people with weak immunity, right before exams run from 14 to 28 October.

Property and records: mold digests paper and spine glue, permanently damaging books and documents. Stains painted over without fixing the cause come back.

Time and reputation: every re-closure of a room costs teaching time, and a musty smell makes students, tenants and customers feel unsafe even when things look clean.

Family: spores travel home on clothes, bags and books, reaching sensitive older relatives or small children.

Why familiar fixes are not enough for Aspergillus

Running fans and waiting: in a room where mold already grows, fans blow spores everywhere and still do not dry wall cavities or stacks of paper.

Wiping with bleach alone: bleach lightens stains on hard surfaces but penetrates gypsum or wood poorly. Never mix bleach with ammonia or some toilet cleaners, as dangerous gases form.

Painting over, or using air freshener: mold under paint stays alive and resurfaces; fragrance masks the smell but removes neither spores nor moisture.

Switching the air conditioning on straight away: wet, moldy filters or ducts send spores to every room they reach.

Disinfecting without removal: this is the most important misconception. Dead mold spores and fragments can still trigger allergies. The CDC and WHO therefore agree that porous materials that were soaked and became moldy must be removed, and hard surfaces must be cleaned until no residue of dirt remains. Disinfection is an additional step after that, not a shortcut that replaces removal and drying.

WHD disinfection spraying: the finishing step after removal, washing and drying

World Health Disinfection (WHD) provides a disinfection spraying service for homes, buildings, offices and schools. According to the service information, trained technicians spray and/or apply an Ultra Low Volume (ULV) fine mist so that the disinfectant coats touch surfaces evenly, including corners that are hard to wipe by hand.

The disinfectant used is CHEMGENE HLD4H, a medical-grade disinfectant from the United Kingdom containing Benzalkonium Chloride and Didecyldimethylammonium Chloride, both quaternary ammonium compounds. According to the product and service information, it is a broad-spectrum disinfectant covering viruses, bacteria and fungi; the service page states 99.99% efficacy, and the product page states 99.85% against COVID-19 within one minute. The website also lists approvals or endorsements from the Thai Department of Medical Sciences, Mahidol University, NHS England and the standard EN 14476:2013+A2:2019, which is the European test standard for virucidal activity.

Being honest about efficacy: the organisms listed on WHD's pages are SARS-CoV-2 (COVID-19), Human Coronavirus 229E, RSV, influenza H1N1 and H5N1, HIV, norovirus, hand-foot-and-mouth virus, vaccinia virus, mycobacteria, Salmonella, Bordetella pertussis (whooping cough), bacteria in general, and fungi or mold. The pages do not list a specific test result for Aspergillus, so we do not claim a kill figure for Aspergillus. What can be said is that Aspergillus belongs to the fungi group the product states it covers, and that WHO and the CDC advise cleaning and then disinfecting surfaces contaminated by floodwater. If your organisation needs test data for this specific organism, ask WHD directly before you decide.

According to the service information, WHD's clients include hospitals, schools, shopping malls, airports, offices, airlines, banks and residential buildings. Tax invoices are available, and the current promotion includes a free CHEMGENE spray bottle and WELLGIENIC wet tissues with the service. For buildings where a musty smell lingers in the air after spraying, WHD's ozone disinfection service can be considered as a complementary option.

The right order of work for a building with Aspergillus

1. Assess the area and keep high-risk people out: identify flooded rooms and rooms with a musty smell or visible mold. People with weak immunity or lung disease should not take part in clean-up.
2. Cut power and check electrical safety: before running blowers or dehumidifiers.
3. Remove porous materials that were soaked or moldy: carpet, ceiling boards, the wet section of gypsum walls, insulation and upholstery. Bag them before carrying them out to limit spore release. For valuable documents, consult a document conservation specialist.
4. Shovel out mud and wash hard surfaces: use water with detergent or a cleaner until no dirt remains. Use a vacuum with a HEPA filter instead of dry sweeping.
5. Dry thoroughly: use dehumidifiers and directed ventilation. Check the moisture level of walls and floors until it returns to normal.
6. Clean the air conditioning: replace filters, clean coils and drain pans, and check duct insulation before switching on.
7. Book WHD for disinfection spraying: technicians spray or ULV-mist CHEMGENE HLD4H onto cleaned surfaces. Everyone must leave the sprayed zone during application.
8. Wait for the re-entry time set by the technicians: according to the service information this is about 30 minutes, after which the space can be used normally. Always follow what the technicians tell you on site.
9. Follow up: watch for smells, stains and symptoms among building users over the following weeks. If mold returns, there is still a moisture source to fix.

10 reasons flooded buildings should use WHD disinfection spraying

1. Mold never arrives alone: a flooded building holds mold, sewage bacteria and viruses on touch surfaces. Disinfection spraying with a product stated to cover all three groups is more practical than targeting germs one at a time.
2. ULV mist reaches where cloths cannot: under bookshelves, behind cabinets, into the gaps of desks and the legs of hundreds of chairs.
3. A medical-grade disinfectant with references: CHEMGENE HLD4H cites EN 14476 and several institutions in its product information.
4. Trained technicians: they close off zones, wear proper protection and apply the right amount.
5. Suited to large spaces: libraries, gyms and multi-storey dormitories are hard for housekeeping alone.
6. Short waiting time: about 30 minutes before use, per the service information, helping you meet class and exam dates.
7. Experience across settings: clients include hospitals, schools, airports and banks, per the service information.
8. Paperwork for institutions: tax invoices, plus certificates or test reports on request.
9. Works with other services: spray surfaces, then add ozone for lingering musty air.
10. Helps you communicate confidence: management can tell students and parents that buildings have been stripped, washed, dried and professionally disinfected.

Before and after: a building that completes every step

Example case: a private dormitory near the campus

(An illustrative example case to explain the order of work, not a real customer review.)

Ton owns a three-storey dormitory in the Bang Kapi area whose ground floor, with eight rooms, a laundry and a storeroom, stood in water for several days. Once it receded, he had the laminate floors, the lower partition walls and every mattress removed, pressure-washed the mud out and ran rented dehumidifiers for three days. The storeroom of cardboard boxes and old blankets smelled worst, so he discarded its contents.

Once the walls were dry, he booked WHD to spray the whole ground floor, including handrails, doors and the laundry. Upstairs tenants kept their doors closed and stayed upstairs until the technicians said they could come down. Only then did he fit new panels, repaint with moisture-resistant paint and raise storage off the floor.

The order is what this case gets right: remove, wash, dry, disinfect, and only then repair visible surfaces. Painting before walls are dry gives a mold such as Aspergillus every chance to return within weeks.

Checklist before and after spraying for teaching buildings and offices

Before spraying

• Wear a particle-filtering mask such as an N95, rubber gloves and boots whenever you enter a moldy area.
• Sort wet documents and books. Discard what is not needed and consult specialists about important records.
• Remove porous materials that were soaked or moldy and seal them in bags.
• Wash hard surfaces with water and cleaner, and vacuum with a HEPA-filter machine.
• Run dehumidifiers until walls and floors are dry.
• Clean the air conditioning and change the filters.
• Remove food, food containers and personal items from the zone to be sprayed, and take out pets and plants.
• Tell building users in advance when areas will be closed.

After spraying

• Wait for the re-entry time set by the technicians.
• Ventilate as the technicians advise.
• Rinse surfaces that touch food directly, such as preparation tables, with clean water before use, as advised.
• Keep indoor humidity under control so mold does not return.
• Watch for new smells and stains over one to two weeks. If they appear, look for leaks or remaining moisture.
• Anyone with ongoing breathing symptoms or a chronic illness should see a doctor.

Frequently asked questions about Aspergillus and disinfection spraying

Q: Can Aspergillus spread from person to person?
A: No. People are infected by breathing in spores from the environment, so reducing mold in buildings is the main form of prevention.

Q: What percentage of Aspergillus does CHEMGENE HLD4H kill?
A: WHD's pages do not list a specific test result for Aspergillus. They state that the product covers the fungi group and give an overall efficacy of 99.99% on the service page. If you need test data for this organism, please ask WHD directly.

Q: If we spray, can we keep moldy ceiling boards or carpet?
A: No. Porous materials that were soaked and became moldy should be removed, because mold grows deep inside them and dead spores still cause allergies. Spraying comes after removal, washing and drying.

Q: Do people need to leave the building during spraying?
A: Everyone must leave the sprayed zone during application and return only when the technicians say so. According to the service information, this is about 30 minutes.

Q: Does the disinfectant leave a residue?
A: We do not claim that it leaves no residue. Surfaces that touch food or that small children may put in their mouths should be wiped or rinsed with clean water as the technicians advise, and all after-spray instructions should be followed.

Q: What if I cough or feel short of breath after returning to the building?
A: Leave the area and see a doctor, mentioning your exposure to a flooded area and mold, especially if you have asthma, lung disease or weakened immunity.

Ready to bring your building back into use with confidence?

Once removal, washing and drying are done, let the WHD team finish the job with CHEMGENE HLD4H disinfection spraying. Ask for test documents and book through any channel.

Book Disinfection Spraying

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

Related links and references

Internal links

• WHD disinfection spraying service
• CHEMGENE HLD4H disinfectant
• Residential and building ozone disinfection
• Certificates
• Contact us

External references

• Thai PBS report on the 2026 Ramkhamhaeng University flood: thaipbs.or.th/news/content/559039
• CDC, Floods (clean-up and mold after flooding): cdc.gov/floods
• WHO fact sheets: who.int/news-room/fact-sheets
• Department of Disease Control, Thailand: ddc.moph.go.th

#Aspergillus #IndoorMold #DisinfectionSpraying #DisinfectionService #PostFloodDisinfection #GermsAfterFloods #RamkhamhaengFlood #Chemgene

Keywords: Aspergillus, indoor mold, post-flood disinfection, mold after flooding, aspergillosis, Ramkhamhaeng University flood 2026, disinfection spraying service, CHEMGENE HLD4H