Last updated: 8 Oct 2026 | 7 Views |
After the water went down in Sai Noi and Bang Yai districts, Nonthaburi, in 2026, many families began finding a dark green powder on the backs of wooden cabinets, under floorboards, on table legs and on wooden doors. Some who farm rice or orchards even remarked that the colour looked like Trichoderma, the fungus Thai farmers know well as a biological product for soil and crop care. So what does it mean when a mold that is useful in the field starts growing indoors? This article answers that question, explains where green mold hides, why wiping does not make it go away, and where post-flood ozone disinfection fits for wooden homes in Sai Noi and Bang Yai.
According to Thansettakij, on 28 September 2026 Nonthaburi announced additional flood disaster zones, bringing the total to 4 districts and 35 subdistricts, including Bang Yai and Sai Noi. In Sai Noi the listed subdistricts include Sai Noi, Sai Yai, Khlong Khwang, Thawi Watthana, Khun Si, Nong Phrao Ngai and Rat Niyom. The report said residential areas had been flooding since 25 September 2026 because of continuous heavy rain and a high Chao Phraya River.
Nationally, the Department of Disaster Prevention and Mitigation (DDPM), as of 06:00 on 7 October 2026, reported 27 provinces plus Bangkok affected, covering 123 districts, 984 subdistricts and 1,154,875 households, with more than 3.1 million people affected. These numbers change daily, so check the latest provincial announcements.
Sai Noi and Bang Yai mix traditional farming communities, rice fields and orchards with fast-growing housing estates. Many homes are still wooden or half-brick, half-wood, with timber floors, solid-wood cabinets used for decades and wooden food safes in the kitchen. Newer estate houses have laminate floors and plywood built-ins. Any wood soaked for days absorbs moisture deep into the grain and becomes an easy place for green mold to grow.
A typical scenario (an illustrative example, not an interview with any specific resident)
Uncle Piak has farmed rice all his life in Sai Noi. His house is half brick, half wood, with a timber ground floor. The main room holds a large teak cabinet inherited from his mother, and the kitchen has a wooden food safe with wire mesh and a long wooden table where the family eats every evening. In late September 2026 heavy rain fell for days. Water entered the house around 25 September and stayed for about a week, high enough to cover the cabinet legs and every floorboard downstairs.
When the water receded, his daughter scrubbed the mud off the floor, washed the outside of the cabinet until it looked clean and left the doors and windows open. Everyone assumed teak could handle water. Within days, though, a thin white fuzz appeared on the back of the cabinet against the wall, then turned into rings of dark green powder. Velvety green spots formed under the bottom drawer. Several floorboards started to warp, and when one was prised up, the underside was coated in green. The main room smelled musty and earthy even with fans running all day.
Uncle Piak looked at it and said it was the same green as the Trichoderma he used to mix into his fields. His five-year-old grandson began coughing at night and sneezing in the mornings, while his wife, who already has asthma, felt short of breath whenever she sat in the main room for long. His daughter wiped the green powder with vinegar. It came off every time, but returned in two or three days, and when she scrubbed hard she could see green dust drifting in the sunlight from the window.
Trichoderma is a group of fungi that live in soil, plant debris and decaying wood. They grow very fast and produce large numbers of spores that are often green, yellow-green or dark green, hence the everyday name green mold. In Thai agriculture, certain Trichoderma types are produced as biological products to help control soil-borne plant diseases, so farmers in many provinces, including Nonthaburi's rice-growing areas, know the name well.
Indoors, its role changes. This mold breaks down cellulose and wood, so it grows on cabinets, floorboards, door frames, plywood, paper and fabric that stay wet. Large numbers of airborne spores act as allergens that can trigger respiratory symptoms in sensitive people, and the mold also stains and weakens wood and creates a musty smell. Put simply, Trichoderma is helpful in soil but is not a mold you want in a bedroom or a food cupboard.
What it usually looks like: a thin white, cobweb-like fuzz at first, then green powder in concentric rings with white edges, with a texture like powder or velvet that puffs up when wiped. However, many green molds look alike, including some Penicillium and Aspergillus species. Only laboratory testing confirms the species. The good news is that household cleanup is almost the same either way.
For farming families: if bags of Trichoderma starter or biological products were stored indoors and got wet in the flood, move them out of the living space to an equipment shed and follow the manufacturer's or agricultural officers' advice. Do not store them with food or in bedrooms.
Warning signs include warped or creaky floors, dark blotches or white residue on wood, a musty smell when a cabinet is opened, green powder in corners, and sneezing or coughing in rooms full of wooden furniture.
For healthy people, Trichoderma does not readily cause infection, but large amounts of airborne spores trigger allergies and irritate the airways. The World Health Organization notes that damp, moldy buildings are associated with coughing, wheezing and asthma flare-ups. Common symptoms after a flood include:
Medical literature describes rare Trichoderma infections in people with severely weakened immunity, such as organ transplant recipients, some dialysis patients and cancer patients during chemotherapy. These cases are uncommon, but they are a good reason for households with such patients to treat mold seriously and keep the patient away during cleaning and sanding.
Others who should take care include young children, older adults, pregnant women, and people with asthma, allergies or chronic lung disease.
Important: If anyone has a fever, wheezing, chest tightness, a persistent cough, or asthma that their usual medicine cannot control, see a doctor promptly and mention the flood and the mold. Ozone treatment is home care, not medical treatment.
CDC guidance is to clean and dry within 24 to 48 hours where possible. Porous materials that soaked for long, such as swollen plywood, particleboard, carpet and mattresses, should generally be discarded, while sound solid wood can usually be cleaned and dried.
Ozone (O3) is a fast-reacting oxidising gas. Released into a closed room, it spreads through the air, behind cabinets, under tables and into cabinets left open, reacting with microbial cell structures and odour molecules before breaking down into oxygen (O2). It leaves no chemical residue on the wood.
According to the company's certification data, the World Health Disinfection ozone service was tested by Thailand's Department of Medical Sciences and Intertek (UK) and eliminated the tested viruses, bacteria and fungi by 99.99%. This article does not claim test results against Trichoderma itself. Trichoderma belongs to the fungi group the service targets, and you can request the test data from WHD or see the certification page.
What ozone helps with
What ozone does not do
Following these rules keeps children and older adults away from ozone entirely, because everyone is outside during treatment and returns once the air is ready.
WHD is based in Bang Khae, Bangkok 10160, with no branch in Nonthaburi. Jobs in Sai Noi, Bang Yai and nearby areas are booked by phone or LINE according to the schedule, and same-day arrival is not guaranteed. Pricing is by quotation after assessment. See the residential ozone disinfection service.
Uncle Piak's daughter stopped dry-wiping and started wearing an N95 mask whenever she cleaned. Her mother and nephew stayed with relatives on higher ground. The teak cabinet was emptied, pulled from the wall and left open. The swollen plywood bottom drawer was replaced, while the teak body was wiped with detergent solution along the grain. A carpenter lifted six warped floorboards, cleared the mud underneath and let the space dry for almost two weeks before relaying them.
Once the wood was dry, the family booked ozone treatment. Everyone spent the day sorting the farm shed while the technician treated the main room, kitchen and downstairs bedroom zone by zone, then ventilated for the set time. The earthy, musty smell that had hung in the main room for weeks was clearly reduced. Uncle Piak said his mother's cabinet would last many more years, as long as its doors are opened to air more often in the rainy season. His wife saw her doctor as scheduled to review her asthma medicine. (This is an example case. Results depend on each home's condition.)
It may be Trichoderma, Penicillium or some Aspergillus species, which look similar. Only a lab can confirm, but home cleanup is the same: clean, dry and discard crumbling materials.
For most people it does not readily cause infection, but heavy indoor spore levels can trigger allergies and asthma, and it can be a concern for people with severely weakened immunity. It should not be left growing at home.
Sound solid wood can usually be cleaned and dried. Swollen, crumbling or delaminated plywood, particleboard or MDF usually needs replacing.
Have a carpenter lift warped or smelly boards, clear the mud, and dry the space fully before relaying. Replace badly damaged boards. Wiping the top alone will not help.
According to the company's certification data, the WHD ozone service achieved 99.99% against the tested fungi, bacteria and viruses. Ozone reduces airborne spores, surface microbes and musty odour, but only after cleaning and drying. Ask WHD for the test data.
No people, pets or plants may be in the room during treatment. The room stays closed for the cycle and is re-entered after ventilation as directed. Following this makes it safe.
It depends on area, room count and site conditions. WHD gives a quotation after assessment. Send photos via LINE @whd268 or call 065-556-6294.
WHD is based in Bang Khae, Bangkok, with no Nonthaburi branch, but it books jobs in Sai Noi, Bang Yai and nearby areas by phone or LINE according to its schedule. Same-day arrival is not guaranteed.
Find the source, often under floors, behind cabinets, in swollen plywood or wet carpet. Clean and dry it, then use ozone to reduce the remaining odour.
Send photos of your furniture, floors and moldy rooms, and the team will help you decide what to do first and when ozone makes sense.
See the Post-Flood Ozone Service
Call 065-556-6294 | LINE @whd268
World Health Disinfection, Bang Khae, Bangkok 10160. Upcountry jobs booked by phone or LINE. Pricing by quotation.
Note: area details and figures follow the dates in news and DDPM reports and change daily. This article is general information, not medical advice.
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