A typical scenario (an illustrative situation based on common cases, not a review from any specific customer)

A one-star review that says "the box smells musty"

Prae has sold skincare and household goods on online marketplaces for five years. She started by packing orders in her condo bedroom; today she rents a medium-sized unit in a warehouse estate on the eastern outskirts of Bangkok. Eight packers work for her. Four-level steel racks run in rows; at the front is a long packing table and a pickup point where riders collect parcels. There is an air-conditioned room for high-value stock, a small staff room and a mezzanine office where she answers customer chats.

Between 24 and 27 September 2026, continuous heavy rain flooded much of Bangkok, and according to news reports the eastern side of the city was hit hardest. The road in front of the estate turned into a river. Water came into Prae's unit under the roller shutters and through the drains at the front, and stayed on the floor for several days. Stock on the lowest pallets got wet along almost the whole row. Rolls of kraft paper, bubble wrap and a fresh order of mailer boxes for the year-end sales were sitting on the floor near the packing table.

When the water went down, Prae and her team quickly pulled out wet stock, washed the floor and reopened for orders within days, because regular customers were waiting. A week later the one-star reviews began. One customer wrote that everything had arrived, but the box smelled so musty, as if it had been stored somewhere damp, that she did not want to use the product. Another sent a photo of small black spots inside the corner of a box. When Prae walked through the warehouse again, she noticed white fuzz along the folds of empty boxes stacked against the back wall, dried mud on the rack legs, a musty smell every time the high-value stock room was opened, and two packers sneezing and rubbing their eyes through every shift.

What worried Prae most was not the reviews already posted but the year-end sales campaigns just ahead, her busiest weeks of the year. Packing thousands of parcels from a warehouse that still had mold and musty air would multiply the problem, and a shop rating built over five years could slide within weeks.

This can happen to many online sellers and fulfilment operators after a flood, because e-commerce does not only ship products. It ships the unboxing experience into the customer's home. This guide explains where mold and germs hide in a warehouse after a flood, why washing the floor is not enough, and where ozone disinfection fits in.

The late-September 2026 Bangkok floods and suburban warehouses

According to news reports, around 300 mm of rain fell in about 48 hours, flooding much of Bangkok, and on 26 September 2026 the Bangkok Metropolitan Administration declared all 50 districts a disaster zone. Eastern Bangkok was hit hard, with areas such as Khlong Chan and Bueng Kum mentioned. Governor Chadchart Sittipunt said the canals were full and drainage would take two to three days after the rain stopped. As of 30 September, some roads such as Si Burapha and Lat Phrao still had 20 to 40 cm of water.

Thai media compared the event with the great flood of 2011, and one Thai business report cited a Thai Chamber of Commerce estimate of about 12,300 million baht in damage. For warehouses and e-commerce, the damage does not end with stock that went under water. It includes disrupted deliveries, delayed orders, and the risk that goods which seem to have survived are shipped out carrying mold and musty smells.

Suburban warehouses have features that make post-flood problems complicated. Most are wide, high-roofed buildings with concrete floors at or just above road level, several large roller shutters, and lots of absorbent material: corrugated boxes, kraft paper, labels, tape and wooden pallets. E-commerce warehouses also have high turnover of people and goods. Staff pick, pack and hand parcels to riders all day, so hands keep carrying germs from one surface to the next.

Where mold and germs hide in a warehouse after a flood

Floodwater entering a warehouse comes from roads and drains, mixed with mud, sewage, oil and waste. It carries bacteria, viruses and mold spores onto every surface. Once it drains away, moisture trapped in concrete, cardboard and wood, plus hot humid air, lets mold grow fast. General advice from the WHO and the US CDC is to clean and dry wet materials within 24 to 48 hours, or mold is likely to start.

Hotspots specific to e-commerce warehouses

• Empty boxes and packing materials. Corrugated board is layered paper with air channels that soak up moisture from floors and air. Even boxes that were never submerged can grow mold along folds and inner corners after days in a damp room.
• Steel racks and wooden pallets. Rack legs with dried mud and pallets that sat in water collect germs, yet look "dry" from above.
• Packing tables and shared tools. Tape dispensers, label printers, barcode scanners and scales are handled by every packer, every shift.
• Air-conditioned stock rooms. If the air conditioner in a closed room for high-value or temperature-sensitive stock got damp, it becomes a machine that circulates spores and musty air all day.
• Returns area. Returned goods from customers in flooded areas can arrive damp and contaminated. Mixed with sellable stock, they spread the risk.
• Staff room and toilets. Where staff eat, store bags and share toilets. If sewage backed up during the flood, these are diarrhoea risk points.
• Rider handover point. Outsiders who may have just waded through water walk in and out all day.

Germs to watch for, and symptoms to notice

Mold is the most visible problem. Spores float in the air and settle on boxes, producing a musty smell customers notice the moment they open a parcel. For staff, constant exposure can cause sneezing, a blocked nose, itchy eyes and coughing, and can trigger allergies or asthma.

Sewage bacteria spread via hands that touch contaminated surfaces, especially in the staff room and toilets, causing diarrhoea, stomach pain and nausea. In a small team, two or three people off sick at once means orders fall behind.

Leptospirosis is a risk for staff who waded in to move stock while the water was high. The bacteria enter through cuts or skin softened by long immersion. Key symptoms are sudden high fever, headache and muscle pain, especially in the calves. Anyone with these symptoms must see a doctor immediately and mention the floodwater exposure. Ozone treats spaces, not disease.

Viruses on shared surfaces. Scanners and label printers used all day are ideal for passing germs from person to person, especially when staff are exhausted from dealing with floods at their own homes.

Who is most at risk?

Packers with allergies, asthma or lung disease, pregnant staff, people with diabetes, and anyone lifting wet boxes or cleaning the warehouse need full protective equipment and should stay out of zones with heavy mold. And remember that every box ends up in a customer's home, which may include small children, elderly people or someone with sensitivities.

What online sellers and warehouse owners stand to lose

Shop ratings and reviews

In e-commerce, customers never see your warehouse. They only see the box at their door. If it smells musty or has black spots, they will not ask what happened at the warehouse; they will leave a low rating straight away. Those reviews stay on your shop page for a long time and influence every new visitor.

Returns and spoiled stock

Goods returned for odour or mold mean two-way shipping, products that cannot be resold and staff time spent on complaints. For items that touch skin, such as skincare, clothing or baby products, customers are even less forgiving, and marketplaces may act against shops with high return rates.

No time to waste

The end of the year is peak season for online shops. If the warehouse still has problems on campaign day, fixing them while orders pour in is extremely hard. Sorting it out now costs far less than dealing with it in the busiest weeks.

Your team and their families

Small online shops run on a handful of people. If packers spend every shift with allergy symptoms, or several get diarrhoea at once, the work lands on the owner. Many staff are also cleaning up their own flooded homes. A clean workplace where they can breathe easily is what they need most right now.

Why washing floors and opening the doors is not enough

Washing the floor without moving stock. Many warehouses clean the aisles but never lift goods and boxes off the bottom level, so mold keeps growing under pallets and behind boxes against the wall.

Bleach on floors and racks. It helps on smooth hard surfaces, but works poorly on cardboard and wooden pallets, does not reach spores in the air, and can leave a chlorine smell that clings to boxes.

Opening the roller shutters for airflow. Ventilation is good, but while outside air is still humid and rain is frequent, open doors can bring in more moisture and blow spores across the warehouse.

Spraying fragrance into boxes. A shortcut some shops take, but perfume mixed with mustiness often smells worse, does nothing about the mold, and can bother customers sensitive to fragrance.

Reusing old boxes that "look fine". Boxes exposed to humidity may already have mold inside the flutes even without obvious water marks. Using them sends the problem straight to your customers.

What is missing is treatment of germs in the air and in places hands cannot reach. That is where ozone comes in, but only after damaged goods are removed and the space has been cleaned and dried.

WHD ozone disinfection for warehouses

According to World Health Disinfection (WHD), ozone (O3) breaks down the cell structures of viruses, bacteria and mold, as well as odour molecules, then reverts to oxygen (O2) without chemical residue. That suits spaces holding goods and packing materials that should not pick up chemical films or smells. According to test results certified for the company, the service was tested by Thailand's Department of Medical Sciences and Intertek (UK), eliminating viruses, bacteria and mold by 99.99%.

Planning for open halls and closed rooms

To be straightforward: ozone works best in enclosed spaces. A wide hall with vents under the roof or doors that do not seal needs an on-site assessment first. The team will help decide which parts suit treatment, such as air-conditioned stock rooms, partitioned packing rooms, staff rooms, toilets and the mezzanine office. Open halls may need temporary partitioning or other measures alongside.

How the work is done

1. Survey the layout. Where did the water reach, which areas can be sealed, and which goods need moving or special mention?
2. Confirm readiness. Wet or moldy goods and packing materials removed; floors and racks washed and dried; no standing water.
3. Clear and seal. Staff, riders, animals and plants out of the zone; doors closed; "no entry" signs posted.
4. Ozone treatment. A typical cycle is about 30 minutes per zone, covering filling and contact time.
5. Rest and ventilate. Ozone breaks down to oxygen, then the zone is ventilated before staff return.
6. Handover with advice. Guidance on keeping stock off the floor and away from walls, humidity control and rotating packing materials.

Warehouses with chemical smells from floor painting or repairs after the flood can also use WHD's ozone chemical-residue and odour removal service. Scanners, packing tables and high-touch surfaces can be wiped with Chemgene HLD4H disinfectant at the dilution on the label.

10 reasons e-commerce warehouses should ozone-treat before the year-end sales

1. It targets the mold behind musty parcels, rather than covering it with fragrance. Customers smell the product, not the warehouse.
2. It reaches behind racks and into corners that wiping cannot, because ozone is a gas that fills the whole room.
3. No residue on goods or packing materials. Ozone reverts to oxygen. Read more on the ozone disinfection service page.
4. Short time per zone. About 30 minutes per zone, so it can be scheduled overnight or on a day with no dispatch.
5. Backed by test results. According to test results certified for the company, by the Department of Medical Sciences and Intertek (UK). See the certification page.
6. It protects your shop rating at the most important time of year, reducing the chance of reviews about smells and mold when orders peak.
7. It helps packers with allergies. After washing, drying and treatment, packing-room air improves and staff can work properly.
8. It limits cross-contamination of new packing stock. Fresh boxes and bubble wrap do not meet spores lingering in the room.
9. It suits air-conditioned high-value stock rooms, which are closed spaces that treat well once the air conditioner has been cleaned.
10. A team that helps you plan, plus a worthwhile promotion: a free medical-grade disinfectant spray with ozone jobs of 15,000 baht or more. Contact us via the service page.

Before and after: a warehouse restored step by step

Note: results depend on the condition of the space and preparation before treatment. This comparison is illustrative.

Example case: pausing orders for two days to fix it properly

Example case (a simulated situation based on typical jobs, not a real customer review)

After the third one-star review, Prae posted a notice on her shop page that dispatch would pause for two days while the warehouse was restored after the flood. She messaged an apology to customers who had received musty boxes and offered replacements once the originals were returned.

Day one. In gloves and masks, the team threw out every empty box that had been in the warehouse during the flood, along with kraft paper and bubble wrap left on the floor. They lifted every item off the bottom racks, checked each one, and pulled anything with wet or stained packaging out of the sales system. Soaked pallets were discarded, floors and rack legs washed, and dehumidifiers left running overnight. An air-conditioning technician cleaned the units in the stock room and mezzanine office.

Day two. The WHD team surveyed the site and recommended ozone for the high-value stock room, the partitioned packing room, staff room, toilets and office. For the racking hall, with vents under the roof, they advised focusing on cleaning, drying and re-laying stock instead. During treatment, every room was sealed and empty. Prae used the time to collect a fresh batch of packing materials, keeping them outside until the rooms were ready.

When orders reopened, new boxes went on raised shelves away from the walls, a separate returns point was set up by the door, and a humidity meter was installed in the stock room. The packers who had been sneezing all day said they could breathe more easily. A packer who had waded in to move stock on the first night and then developed a fever was sent to see a doctor first. The following week's reviews were about the products, not the smell of the boxes.

Warehouse flood-recovery checklist

Safety

• Keep flooded circuits off until an electrician checks them. Watch forklift battery chargers and extension leads on the floor.
• Wear boots, gloves and a mask, and cover all wounds when cleaning.
• Check rack bases for rust or sinking after immersion before loading heavy goods.

Before ozone

• Discard wet or moldy boxes, packing materials and wooden pallets.
• Pull goods with damaged packaging out of the sales system immediately.
• Wash floors, racks and packing tables, then dry thoroughly.
• Clean air conditioners and replace filters.
• Remove food and personal items from the staff room.
• Tell the team about sensitive goods so you can decide whether to move them.
• Choose a time with no staff or riders coming and going.

During and after treatment

• The zone must be empty of people, animals and plants, with "no entry" signs.
• Re-enter only after the rest and ventilation period the team specifies.
• Keep stock off the floor and away from walls; install a humidity meter.
• Keep a separate returns zone and inspect returned boxes before they enter main stock.
• Wipe scanners, label printers and packing tables daily.
• Anyone with fever, calf pain, diarrhoea or infected wounds after wading should see a doctor immediately.

FAQ: ozone disinfection for warehouses after a flood

1. Can ozone save goods that were submerged?

Do not expect that. Goods and packaging that were submerged or have grown mold should be taken out of sale. Ozone treats the space and the air after damaged items are removed and the area is cleaned.

2. Our warehouse is a big open hall with a high roof. Can it be treated?

The team needs to assess it on site. Ozone works best in enclosed spaces. Partitioned rooms such as stock rooms, packing rooms and staff rooms treat well; open halls may need partitioning or other methods alongside.

3. How long do we need to stop dispatch?

A typical cycle is about 30 minutes per zone, plus rest and ventilation. Many shops schedule it overnight or on a day off. Actual time depends on the number of zones and preparation.

4. Will ozone leave a smell on products?

According to the service information, ozone reverts to oxygen and leaves no chemical residue. After the rest and ventilation period, the space is ready to use.

5. Can staff stay in the warehouse during treatment?

No. The zone being treated must have no people, animals or plants, and re-entry is only after the rest period the team specifies.

6. What if a staff member falls ill after wading to move stock?

They should see a doctor and mention floodwater exposure, especially with high fever and calf pain. Ozone is not a medical treatment.

Let every box leave your warehouse with confidence

Talk to the WHD team about a warehouse survey and an ozone plan before the year-end order peak.

Book a warehouse survey and ozone treatment

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

Related services

• Residential and building ozone disinfection
• Ozone chemical-residue and odour removal
• Ozone cleaning service
• Chemgene HLD4H medical-grade disinfectant
• Contact us

References

• 2026 Bangkok floods (Wikipedia)
• Al Jazeera: Disaster zone declared across Bangkok
• CDC: Floods
• WHO fact sheets