A Typical Scenario: A Packaging Warehouse in Ayutthaya

(A typical scenario based on situations we commonly encounter. Names and details are illustrative.)

Ake manages the warehouse of a company in Bang Pa-in, Ayutthaya, that distributes paper packaging and raw materials to snack manufacturers. The building is a large steel-frame shed with a metal-sheet roof and five-level pallet racking. It holds flat-packed corrugated cartons, rolls of kraft paper, sacks of flour and bags of sugar waiting for delivery to several customers.

That year the northern runoff arrived faster than expected. The team had one night to lift what they could onto the upper racks, but pallets on the bottom level and stock stacked on the floor sat in about a metre of water for nearly two weeks. When the water receded, the floor was covered in several centimetres of mud and the whole building smelled of stagnant water.

The team hosed the floor, threw out everything that had been submerged, and quickly brought down stock from the upper levels that "looked untouched" so they could ship overdue orders. Wooden pallets that had been underwater were washed and reused because new pallets were hard to find. Just ten days after the water left, the warehouse was running normally again.

Three weeks later, a major customer emailed photos of cartons with black and green mold spots along the fold lines. Another customer reported that flour sacks smelled musty and asked to return the whole lot. Ake walked the aisles himself. White bloom was appearing on dozens of pallets. Cartons on the second level, which had never touched the water, felt soft and smelled of wet paper. Two forklift drivers mentioned that they coughed and had itchy noses whenever they drove into the back section.

The problem was not only the stock that had been submerged. It was the air in the entire building, saturated with humidity after the flood; the mud still lodged in floor joints and around rack feet; and the damp cores of reused pallets, all releasing spores that settled on goods at every level. Ake learned the hard way that warehouse recovery has to be planned as a system, not just "throw out the wet stuff and carry on."

Deep Dive: Mold in Warehouses and Factories After Flooding

Why warehouses are high-risk

Warehouses and factories have features that make post-flood mold especially aggressive. First, there is a huge volume of air. A building many metres tall filled with saturated air takes far longer to dehumidify than a house or office. Second, metal-sheet roofs heat up by day and cool at night, causing condensation that drips onto the top level of stock. Third, much of the inventory is organic: paper, corrugated board, wood, fabric, fibres, flour, grain and leather, all direct food for mold. Finally, tightly packed stacks leave little airflow between pallets, so moisture stays trapped inside.

The WHO and CDC advise cleaning and drying water-damaged areas within 24 to 48 hours to limit mold growth. For a warehouse flooded for a week or more, that window closed long before anyone could get inside. Mold often starts to establish itself while the water is still standing.

Mold types commonly found in storage

• Aspergillus is common on grains, flour, nuts and damp materials. Some species, such as Aspergillus flavus, can produce aflatoxins, which are well known to be harmful to the liver and are not easily destroyed by ordinary cooking.
• Penicillium often appears blue-green on paper, cardboard, fabric and dry foods, releasing large numbers of spores into the air.
• Cladosporium shows as dark green to black spots on wood, walls and damp packaging.
• Rhizopus and other fluffy molds grow fast on starchy or sugary materials, first as white cottony threads and then black dots.

How contamination spreads through a warehouse

After the water drops, mold is not limited to what was submerged. Spores from damp pallets, mud in floor joints, water-soaked block walls and wet cartons waiting to be removed ride the airflow from industrial fans, passing forklifts and loading-dock doors opening and closing. They land on perfectly dry goods higher up. If those goods then sit in humid air, the spores germinate. That is why cartons that "never got wet" can still go moldy.

Floodwater in warehouses is also frequently contaminated with sewage and rat urine, leaving bacteria on floors, rack legs and pallets. Rats that fled the water and nested among the stock increase the risk of leptospirosis for workers handling goods.

Symptoms and who is most at risk

Workers in heavily contaminated warehouses may experience a blocked nose, sneezing, coughing, stinging eyes, itchy skin, headaches and fatigue. People with allergies or asthma can have flare-ups. Those with weakened immunity, older workers, pregnant employees and anyone with chronic lung disease should avoid working in areas that have not yet been restored. Particularly risky tasks include breaking down moldy stacks, sweeping dried mud and moving old pallets, all of which throw spores into the air.

Health warning: any worker who waded through floodwater or handled wet stock and then develops sudden high fever, headache, muscle pain (especially in the calves) or red eyes should see a doctor immediately and mention the flood exposure, as this may be leptospirosis. Diarrhoea or a persistent cough also warrants medical attention. Ozone treats the space; it does not treat illness.

Damage That Spreads Far Beyond the Flooded Pallets

1. Worker health and safety

Warehouse and production staff spend many hours a day inside. If the air is full of spores and musty odour, allergy and respiratory symptoms interfere with work. A forklift driver with a headache or sore eyes may lose focus, raising the risk of accidents. When staff feel their workplace is unsafe, turnover can rise at exactly the moment the business needs every pair of hands.

2. Money lost to spoiled stock, claims and recalls

Goods that turn moldy after delivery cost more than their own value: return freight, lost opportunity, contractual penalties and, for food ingredients, potentially a lot-wide recall from downstream customers. Moldy packaging makes the product inside look untrustworthy even when the product itself is fine. Corrugated board that absorbs moisture also loses stacking strength, risking collapse when stacked high and damaging more stock underneath.

3. Time and production capacity

Recounting inventory, sorting good from bad, waiting for quality-control checks and reworking when mold shows up in shipped lots all consume time and labour. Production lines may stop while waiting for approved materials, and repeated problems force the whole month's plan to change.

4. Credibility with partners and audit results

Factories producing food, pharmaceuticals, cosmetics or food-contact packaging are audited by authorities and customers against systems such as GMP or HACCP. Traces of mold on walls, pallets or packaging can become major non-conformities. Some export customers may suspend orders until they see clear evidence of remediation. Trust built over years can be shaken by a handful of claims.

5. Workers' families and the local community

Many employees live in communities near the plant that also flooded. If the workplace is not safe either, they carry risk at home and at work. Clothes and shoes exposed to moldy dust go home to young children and elderly relatives. Restoring the site properly is both a duty to staff and a signal to the community.

Why Common Post-Flood Warehouse Fixes Fall Short

• Washing the floor and restocking immediately. A concrete slab looks dry on top within a day or two but keeps releasing moisture for much longer. Putting pallets and goods down too early traps that moisture beneath the stock.
• Washing wooden pallets and reusing them straight away. Wood soaked for days absorbs water deep into its core. Washing the surface does not dry the inside, so the pallet becomes a mold incubator that seeds every item placed on it.
• Spraying disinfectant on walls and floors only. Spraying treats the surfaces the droplets reach, but not the enormous air volume, the underside of the roof, the back of racking or the gaps between stacks. Heavy liquid spraying also adds moisture to a building you are trying to dry, and may leave residues unsuitable for some products.
• Running industrial fans all day. Fans help ventilation, but while mold sources remain, they simply spread spores around the warehouse faster.
• Wiping mold off cartons and shipping anyway. Wiping makes a carton look clean for a while, but hyphae embedded in the paper survive and reappear during transport or in the customer's own storage.
• Painting or epoxy-coating damp floors and walls. Coatings peel away in sheets and seal moisture underneath, hiding the problem until it returns worse than before.
• Relying on rat traps and bait alone. Rodent control is essential, but it does not deal with the contamination rats left on floors and stock, nor the odours that attract pests back.

The key lesson: a warehouse must be treated for both surfaces and air, and only after contaminated stock has been sorted out, not while spoiled goods are still piled across the floor.

WHD Ozone Disinfection for Warehouses and Factories

World Health Disinfection (WHD) provides residential and building ozone disinfection for homes, condos, hotels, offices, factories, schools and hospitals. For a flooded warehouse or plant, ozone treatment comes after mud removal, sorting and disposal of contaminated goods, cleaning and drying. Its job is to reduce residual microbes and odours in the air, on racking, under the roof and in corners workers cannot reach, before stock returns to the space.

How ozone works

Ozone (O₃) is a powerful oxidising gas. Spread through an enclosed space, it breaks down the cell structures of viruses, bacteria and mold and breaks apart the molecules responsible for musty and stagnant-water odours. It then reverts to oxygen (O₂), leaving no chemical residue on racks, floors or walls, which matters in areas that store raw materials and packaging. Because it is a gas, ozone reaches behind racking, into roof voids and gaps that spray droplets miss.

According to the test results certified for the company, WHD's service has been tested and certified by Thailand's Department of Medical Sciences and Intertek (UK) for eliminating viruses, bacteria and mold by 99.99%, which you can include as supporting evidence in remediation reports for partners. See the certification documents.

The warehouse and factory ozone process

1. Survey and zoning. The team walks the warehouse, raw-material stores, packing rooms, production areas, staff rooms and site offices, then divides them into zones that can be closed off, for example with roller doors or temporary tarpaulin partitions.
2. Joint preparation with the plant. Goods that must be stored separately are moved out, loading doors, vents and extract fans are closed, every shift is told the zone is off-limits, and all people, animals and plants are removed.
3. Ozone release. Generators are positioned at suitable points so the gas spreads through the zone.
4. Contact time. Ozone reacts for the specified time. A typical cycle is about 30 minutes per zone; large sites may need several zones or rounds.
5. Rest and ventilation. The ozone reverts to oxygen, then doors and fans are opened to ventilate before staff are allowed back in on the team's instruction.
6. Handover. The team summarises the zones treated and advises on humidity control before stock goes back on the shelves.

Safety and scope: ozone treatment is carried out only in an empty, closed space, with no workers, animals or plants in the zone, and re-entry only after the rest and ventilation period. Just as important, food, food ingredients or goods that were in direct contact with floodwater or are already moldy must be judged under food-safety rules and by your quality-control team, and generally should be discarded. Ozone does not make contaminated food safe, and it does not remove mycotoxins already formed in raw materials.

Promotion: for ozone jobs of 15,000 baht or more, receive a free medical-grade disinfectant spray for shared touchpoints in staff rooms and site offices.

10 Reasons Warehouses and Factories Choose WHD Ozone Before Restocking

1. It treats the whole air volume, not just the surfaces spray reaches, which suits tall, wide buildings.
2. It reaches behind racking and under the roof, places workers would need scaffolding or a lift to wipe.
3. No chemical film on shelving or floors. Ozone reverts to oxygen, suitable for packaging and raw-material stores.
4. It removes musty and stagnant-water odours at the source before they seep into new cartons and incoming stock. See the WHD ozone service.
5. It adds no moisture, unlike heavy liquid spraying that puts more water into a building you are drying.
6. Backed by testing. According to the company's certified results from the Department of Medical Sciences and Intertek (UK), 99.99% elimination of viruses, bacteria and mold, useful in partner communications.
7. Zoned around your shifts, one room or one building at a time so the rest of the plant keeps running.
8. Short cycles, about 30 minutes per zone per round, easy to fit around the production schedule.
9. A professional team controlling safety, sealing zones, checking no one remains and setting clear re-entry times. Ask for details on our ozone disinfection page.
10. A foundation for a site-wide hygiene plan, alongside our disinfection service and ozone disinfection machines for ongoing care, plus the free medical-grade spray on jobs from 15,000 baht.

Example Case: A Small Garment Factory in Ubon Ratchathani

(An illustrative example case, not a named customer review.)

Prae owns a uniform-sewing factory with about fifty workers not far from the Mun River in Ubon Ratchathani. The fabric-roll store and sewing supplies are on the ground floor. When the Mun overflowed, water flooded the storeroom to roughly mid-shin for several days. Rolls stored on the floor were ruined, but those on high shelves seemed to survive.

After the water receded, the team washed the floor and used the good-looking rolls to cut uniforms for customers on schedule. Soon a school customer reported that the uniforms smelled musty even after washing, and some had small blotches along the folds. Several sewing operators complained of itchy noses whenever they unrolled fabric.

Prae stopped using fabric from that room entirely. Quality control inspected each roll and set aside any with odour or spots. Water-soaked wooden shelving was removed and replaced with steel racks, and dehumidifiers ran until walls and floor were fully dry. Only then did she book WHD to ozone-treat the fabric store and sewing floor on a Sunday, in three zones, with the factory closed all day and staff returning after the ventilation period.

In this example, when work resumed on Monday, the storeroom no longer smelled musty. Prae began receiving new fabric onto raised steel racks, set a humidity threshold for the room and had shift leaders log readings daily. Operators with ongoing allergy symptoms were advised to see a doctor. Her takeaway: decisive stock sorting and thorough drying must come first; then ozone can close out the job effectively.

Warehouse and Factory Flood Recovery Checklist

Before entering

• Have an engineer or electrician inspect wiring, control panels and machinery before restoring power.
• Check racking and shelving for stability, settlement or tilting after submersion.
• Workers should wear boots, rubber gloves, suitable dust masks and safety glasses.
• Photograph and log all damaged lots for insurance and accounting.

Sort, clean and dry

• Have quality control sort stock into "discard," "further inspection" and "usable." Food and food ingredients that contacted floodwater should be discarded.
• Remove all mud, especially from floor joints, rack feet and drainage channels.
• Discard or quarantine wooden pallets that soaked for long periods; consider plastic pallets during recovery.
• Wash floors, walls and racking, then disinfect following product instructions.
• Run dehumidifiers and ventilation until floors and walls are truly dry; confirm with a moisture meter if available.
• Check for condensation under the roof and repair damaged roof insulation.

On ozone day

• Coordinate with every shift leader, close the zone and post no-entry signs.
• Confirm no people, animals or plants remain, including small rooms and under-stair spaces.
• Close loading doors and extract fans as advised.
• Re-enter only when the team confirms the rest and ventilation period is complete.

After ozone

• Store goods on dry pallets with gaps from walls and between stacks for airflow.
• Log warehouse humidity and temperature daily and use first-in, first-out so stock doesn't linger.
• Inspect stock on a schedule for spots and musty odour along carton folds.
• Maintain continuous rodent and pest control.
• Any worker with unusual symptoms should see a doctor and mention flood exposure.

Frequently Asked Questions

Q: After ozone treatment, can we sell food products that were submerged?
A: No. Food and food ingredients that touched floodwater or have gone moldy should be discarded under food-safety principles. Ozone treats the space and air; it does not make contaminated food safe.

Q: Our warehouse is huge. Can it be treated thoroughly?
A: The team surveys the site, divides it into zones that can be sealed and treats them one at a time or in multiple rounds. A typical cycle is about 30 minutes per zone.

Q: Do we have to stop production across the whole plant?
A: Not necessarily. With clearly separated zones, only the empty zone is treated while other areas keep working. The treated zone must stay completely empty until ventilation is complete.

Q: Should we treat before or after bringing in new stock?
A: After spoiled stock is removed and the space is cleaned and dried, but before new goods arrive, so the area is in its best condition. If some stock must stay in place, tell the team beforehand so you can assess it together.

Q: Can ozone affect machinery or certain materials?
A: The team assesses the space and materials first and advises what to move or protect. Share a list of sensitive equipment and materials in advance.

Q: Can we get documentation to show customers or auditors?
A: Ask the team about a job summary, and see the company's certified test results on the certification page.

Q: How do we request a quote?
A: Call 065-556-6294 or LINE @whd268 with your floor area, product types and flood depth, or use the other channels on our contact page.

Get Your Warehouse Ready Before the Next Shipment Arrives

Talk to WHD about post-flood ozone treatment for your warehouse or factory, zoned around your floor plan and production schedule.

Request a Warehouse Ozone Assessment

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

Related Services

• Residential and Building Ozone Disinfection
• Reducing Chemical Residue with Ozone
• Ozone Disinfection Machines
• Disinfection Service

References

• CDC – Floods: cleanup and safety
• Department of Disease Control, Thailand Ministry of Public Health