A Story from the Field: Chai's Granary Is Not the Same Anymore

Chai runs a mid-sized rice mill in Tha Tako district, Nakhon Sawan province, a business he took over from his father. Every season he buys paddy from farmers in the surrounding subdistricts, mills it into white rice and sells it to shops and markets across the province. Beside the mill stand two large paddy warehouses and an old wooden granary his father built when Chai was still a boy. The granary is more than storage to him; it is a piece of family history, with his father's initials carved into one of the posts. Every year, at the end of the rainy season, Chai prepares the warehouses to receive the main-season harvest that farmers are about to bring in.

This year the rain simply kept falling. Water from the low-lying land around Bueng Boraphet and the nearby waterways spread across the fields and into the mill compound. Inside the warehouses it rose more than half a meter. Dozens of sacks of unsold paddy on the bottom layers were submerged. Chai and his workers worked through the night lifting dry sacks onto higher stacks, but there was only so much they could move before the water reached the electrical panels and they had to cut the power and leave.

Two weeks later, when the water finally drained away, Chai pulled open the warehouse doors. A wall of heavy, damp mustiness rolled out, mixed with the sour smell of rice that had begun to ferment. He actually took a step back. The submerged paddy had sprouted, and green-and-black mold covered the sacks. The concrete floor was coated in sticky mud. On the wooden walls of the granary, a band of mold ran along the exact line the water had reached. Every time someone moved a sack, a cloud of dust and spores drifted up into the light from the doorway. Two of his workers began coughing and sneezing within minutes.

Chai was not only worried about what he had already lost. He was worried about what he might lose next. The harvest was weeks away. If he brought new paddy into a warehouse whose air was still full of mold spores, the entire new lot could be damaged too. And a rice mill lives on its reputation for clean, good-smelling rice. One bad season could undo decades of trust with his buyers.

Across Nakhon Sawan, Phitsanulok, Ayutthaya and Suphan Buri, many mill owners, rice traders and farming cooperatives are standing in front of the same open warehouse doors this October. This article explains why flooded grain storage is such fertile ground for mold, why the usual quick fixes rarely hold, and how ozone treatment combined with disinfection fogging can get empty storage ready for the new harvest.

Why Flooded Rice Storage Becomes a Perfect Breeding Ground for Mold

Paddy, husks, bran dust and timber all absorb moisture easily. When a flood is followed by the hot, humid weather typical of a Thai October, mold grows extremely fast. Within days, a damp warehouse can go from smelling slightly stale to being visibly colonized. The damage falls into three broad areas.

Health risks

• Airborne mold spores. A warehouse with heavy mold growth releases clouds of spores every time sacks are moved or the floor is swept. Workers may cough, sneeze and feel irritation in their nose and throat, and people with allergies or asthma can suffer attacks. Long hours in dusty, moldy air are tiring and unpleasant even for healthy workers.
• Mycotoxins. Some molds that grow on grain can produce toxins, aflatoxin being the best known. This is why paddy that was submerged or has visible mold should not be eaten, sold for food or mixed with good grain. It should be separated and handled according to advice from the relevant authorities.
• Leptospirosis. Grain warehouses attract rats, and floodwater spreads bacteria from rat urine across floors and walls. Workers who clean up in mud without boots and gloves face a real risk of leptospirosis, which can begin with fever and muscle pain that are easily mistaken for flu.
• Flood-borne germs. Floodwater carries bacteria such as E. coli from sewage and animal waste. Contact with contaminated mud can lead to diarrhea and skin infections, especially through cuts and scratches.

Business risks

The damaged paddy is already a loss, and there is little that can be done about it. The bigger danger is that a warehouse still harboring mold will ruin the next lot as well. Milled rice with a musty smell or grains with mold spots gets marked down or rejected by buyers. Traders talk to each other, and a mill that ships musty rice once may find buyers checking every delivery more carefully, or quietly moving to a competitor. A reputation built over generations can be badly dented in a single season.

There are also knock-on costs. Moldy warehouses attract more insects, which damage grain and packaging. Wooden structures that stay damp start to rot, leading to repairs that could have been avoided. And workers who feel unwell in a moldy environment are slower and more likely to take sick days just when the mill needs everyone on hand.

Time pressure

The harvest waits for no one. If the warehouses are not ready when farmers start bringing in their paddy, the mill either loses the chance to buy or must rent storage elsewhere, adding transport costs and complications. Farmers who cannot sell to their usual mill may sell to someone else, and some of them may not come back. Getting the storage clean, dry and safe quickly is therefore a commercial priority, not just a hygiene task.

It is also worth remembering that the mill itself is only one part of the picture. Offices, worker housing, toilets and the drying yard were often flooded at the same time, and each of these areas can harbor the same germs and mold. A recovery plan that treats the warehouse but ignores the rooms where workers eat and sleep leaves people exposed, and it can bring contamination straight back into the clean storage on boots, clothes and tools. Thinking about the whole compound from the start saves time and avoids repeat work later.

Why the Usual Fixes Don't Keep Mold Away

Mill owners are practical people, and the first instinct is to sweep up, open the doors and let the sun do the rest. These steps help, but on their own they rarely solve the problem.

• Sweeping and leaving the doors open. This lets air in, but mold spores embedded in timber, floor cracks and the roof structure remain exactly where they were. As soon as humidity rises again, they start growing.
• Pouring bleach. Bleach is hard to apply evenly across a large warehouse. It has a strong smell, does not penetrate wood well, loses strength when it meets mud, and can leave an odor that grain may absorb later.
• Sun-drying or running fans. Only part of a warehouse can be reached by the sun, and fans tend to blow spores around the building rather than remove them, spreading contamination into areas that were clean.
• Painting or oiling over the walls. This hides stains for a while, but the mold underneath returns while moisture remains. Flaking paint later adds dust and debris to the storage area.
• Rushing new grain in. It is tempting to fill the warehouse to keep up with the season, but fresh paddy that still carries some moisture is exactly what lingering spores need to thrive.

The core of the problem is that mold in a warehouse lives both on surfaces and in the air. If you only deal with one, the mold comes back sooner than you expect. A large, tall building with timber beams and corrugated roofing has a huge amount of surface area and an even larger volume of air, and both need attention.

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

World Health Disinfection (WHD) provides ozone shock treatment that is well suited to large enclosed spaces such as warehouses and granaries. Ozone is a reactive gas that spreads through the entire building, reaching the roof structure, the gaps between timber boards and every part of the air. It helps deal with mold spores and breaks down the molecules responsible for musty and fermented odors.

This is combined with our disinfection fogging service using Chemgene HLD4H, a high-level disinfectant with broad activity against bacteria, viruses and fungi. ULV foggers turn the solution into a fine mist that settles evenly on floors, walls, posts and beams, treating the flood germs left on surfaces.

Important: fogging and ozone treatment are carried out in warehouses that have already been emptied of grain and sacks. This service restores the building; it does not make moldy grain safe to sell or eat. Paddy that was submerged or has grown mold should be separated and handled according to guidance from the relevant authorities.

Our step-by-step process for rice mills and grain warehouses

1. Site survey. Our team inspects the warehouses, granary, drying yard and milling room. We assess how much mold is present, where water pooled, and which equipment needs protection, such as conveyor belts, motors and electrical panels.
2. Removal and mud clean-up advice. We advise on removing damaged paddy, sacks and wet husks, scraping out mud and washing floors. Disinfection works best when there is no thick layer of dirt for germs to hide under.
3. Chemgene HLD4H fogging. We fog the floors, walls, posts, beams and the area around the milling room to deal with flood germs on surfaces.
4. Ozone shock treatment. The warehouse is closed up and the ozone generators run for a period matched to its volume, targeting spores in the air and roof spaces as well as odors soaked into the timber.
5. Ventilation. Doors and vents are opened until ozone falls to a safe level before workers return.
6. Re-check and advice. We check odor and visible mold with the owner and advise on moisture control before new grain is brought in.

Why the two methods work better together

A flooded grain warehouse has two layers of contamination. The first is on the surfaces: mud residue, bacteria from floodwater and visible mold on floors, walls and posts. The second is in the volume of the building: spores floating in the air, spores lodged in the roof structure and odors absorbed into wood. Fogging is the right tool for the first layer, while ozone is the right tool for the second. Using only one leaves half of the problem untouched, which is why mold so often seems to "come back" a couple of weeks after a quick clean-up.

10 Reasons Rice Mills in Tha Tako Choose WHD to Restore Their Storage

1. Built for large enclosed spaces. Ozone spreads through the whole warehouse and granary, with no need to wipe every board by hand.
2. Airborne spores are tackled, reducing the chance that mold returns to the walls or the next lot of grain.
3. Musty and fermented odors are broken down, not masked, so new grain does not pick up the old smell.
4. We use Chemgene HLD4H, a high-level disinfectant with broad activity against bacteria, viruses and fungi.
5. ULV mist reaches beams and roof frames that are dangerous and slow to clean by climbing.
6. Ready in time for harvest. We plan the work so your storage can receive the main-season crop on schedule.
7. Mill machinery is protected. Belts, motors and electrical panels are covered or isolated before treatment.
8. Worker safety is built in, with clear closure, signage and ventilation before re-entry.
9. Everything in one service, from warehouses and milling rooms to offices and worker housing, with optional mosquito spraying around the compound.
10. Easy to contact. Call 065-556-6294 or message LINE @whd268 to book a warehouse survey.

Before and After Ozone Treatment and Disinfection Fogging

Long-Term Care: Keeping Mold from Coming Back

Disinfection fogging and ozone treatment after a flood give your storage a fresh start, but keeping mold away over the long term depends on everyday habits. Mold needs three things to grow: moisture, food and a suitable temperature. A grain warehouse in central Thailand already has plenty of food and warmth, so the factor an owner can control most is moisture. The good news is that most moisture problems are visible and fixable if you know what to look for.

• Inspect the roof and gutters after every storm. A single leak dripping onto a stack of paddy is enough to start a patch of mold that can spread through the whole pile.
• Use ventilation wisely. Open vents and doors when the air is dry, and close them during rain or very humid spells, so the building does not pull in damp air.
• Rotate stock first in, first out. Do not let old lots sit forgotten in a corner of the warehouse for months. Older grain is more likely to develop problems and can then contaminate newer stock nearby.
• Clean up bran dust and husks regularly. Dust collecting on beams and in corners is food for both mold and insects. A monthly sweep of high surfaces pays for itself.
• Watch for early warning signs. A musty smell, condensation under the roof sheets, or dark spots on sacks all suggest moisture is building up. Deal with them straight away rather than waiting for the next season.
• Keep records. Note moisture readings, treatment dates and any problem spots. Over a few seasons, patterns will emerge that help you plan maintenance before trouble starts.

If a musty smell returns in the future, scheduling ozone treatment while the warehouse is empty between seasons is a straightforward way to keep the storage environment in good condition year after year. Many mill owners find it easier to plan this as part of their regular pre-harvest preparation, alongside roof checks and pest control, rather than waiting for a problem to appear.

In His Words: A Mill Owner's Perspective

"At first I thought sweeping up and leaving the doors open would be enough, but a week later the smell was still there. The team told us to get all the spoiled material out first, then they did the fogging and the ozone. When we opened the warehouse the next day, it smelled completely different, and my guys stopped coughing. This year I could take in the new harvest without that knot in my stomach."

— Chai, rice mill owner, Tha Tako, Nakhon Sawan (field scenario)

Checklist Before Bringing the New Harvest into Storage

• Separate damaged grain. Remove all paddy that was submerged, has sprouted or shows mold, and never mix it with good grain.
• Clear out wet materials. Take out sacks, husks and bran that got wet. They hold moisture and spores.
• Scrape and wash. Remove mud and wash floors, walls and drainage channels.
• Electrical safety. Have an electrician inspect the mill's motors, panels and wiring before switching the power back on.
• Disinfect and treat the air. Fog the surfaces and use ozone to deal with airborne spores and musty odor.
• Dry thoroughly. Let the building dry completely and look for leaks or seepage in the roof and walls.
• Use pallets. Stack grain on pallets, away from walls and off the floor, so air can circulate.
• Check moisture content. Test the moisture of incoming paddy before storage and plan rodent and insect control.
• Protect workers. Masks, gloves and rubber boots should be worn during clean-up. Anyone who develops fever or muscle pain after wading through floodwater should see a doctor promptly.
• Keep an eye on it. Walk the storage regularly in the first weeks after the harvest arrives, checking for musty smells, condensation or new spots of mold.

Frequently Asked Questions (FAQ)

Q: Can ozone treatment make moldy paddy sellable again?
A: No. This service restores warehouses and granaries that have been emptied. Grain that was submerged or has grown mold should be separated, because it may contain mold toxins.

Q: Can you treat an old wooden granary?
A: Yes. Ozone reaches gaps between boards and the roof structure well. We will assess the condition of the timber and recommend repairing any rotten sections before storing grain.

Q: How long do workers need to stay out during ozone treatment?
A: It depends on the size of the warehouse. We will give you clear treatment and ventilation times. No people, animals or plants may be inside until ventilation is complete.

Q: Will the mill machinery or belts be damaged?
A: We control the ozone dose and cover or isolate rubber parts and electronics before treatment.

Q: How often should this be done?
A: After a flood we recommend treatment before new grain is stored. After that, it depends on humidity and how the warehouse is maintained. Ask our team at 065-556-6294.

Q: Do you serve areas outside Nakhon Sawan?
A: Please ask about service areas via LINE @whd268.

Get Your Storage Ready Before the New Harvest Arrives

Don't let mold from this flood ruin your next lot of rice. Talk to the World Health Disinfection team today.

Book Ozone Treatment – Click Here

See Our Disinfection Service – Click Here

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

Related Links

• Ozone treatment for odor and chemical residue removal
• Master Ozone Generator
• Residential ozone disinfection (worker housing)
• All articles from WHD
• External sources: WHO – Floods and health and Department of Disease Control, Thailand