A 900 Square Metre Dry Food Warehouse Where Mould Cost 1.9 Million Baht in Returned Stock
Last updated: 6 Sep 2026 | 6 Views |
Stock that is not spoiled but cannot be sold, because the smell travels with the carton
A 900 Square Metre Dry Food Warehouse Where Mould Cost 1.9 Million Baht in Returned Stock
Why mopping and charcoal bags did nothing, and why ozone is the answer for food storage
The product was not spoiled and the packaging was not damaged, yet the customer rejected the whole consignment because opening the box released a musty smell. This is the story of a warehouse that looked spotless and had a problem in its air.
Khun Somchai is 52 and owns a dry food distribution business in Samut Sakhon. His 900-square-metre warehouse holds dried noodles, flour, spices, nuts and packaged dried goods for more than 200 retail outlets across central Thailand.
In August 2025, in the middle of the rainy season, two major customers returned consignments at the same time, worth 1.9 million baht together. Both return notes gave the same reason: abnormal musty odour in the goods.
Khun Somchai opened the cartons and checked bag by bag himself. Nothing was out of date, no bag was punctured, there was no sign of insects and no visible mould on any product. But when he put his nose to the cardboard carton itself, he understood immediately that his customers were right.
The story
The smell that travels with the carton
What he discovered that day was that the musty odour was not in the product. It was in the corrugated cartons, in the packing tape, and in the wooden pallets the goods were stacked on three metres high.
Corrugated board is extremely porous and absorbs both moisture and odour exceptionally well. When cartons sit for weeks in a warehouse at over 80 percent relative humidity, the board takes in both the moisture and the odour molecules in the air and stores them.
When the carton then travels to a retail outlet and is opened in an air-conditioned room at lower humidity, everything it stored evaporates out at once. Staff open the box, get a face full of musty air, and refuse to take the goods into stock.
The product itself may be perfectly fine. But in the food business, the recipient's perception is the reality, and no retailer will risk shelving goods that came out of a box that smells.
What they found when they went up to the roof
Khun Somchai hired an engineer to inspect the whole building. Three things came back. First, two small seepage points at the metal sheet roof joints — not enough to drip, but enough to let moisture accumulate in the structure.
Second, the warehouse's ventilation relied mainly on roof turbine vents. Those work well when there is wind. In the rainy season, with still air and high humidity, the air in the warehouse barely moved all day.
Third, and the real culprit: the pallets. More than four hundred wooden pallets in rotation had mould growing on their undersides and along the splits in the timber, invisible because pallets are always stacked with goods on top of them.
Damp, mouldy wooden pallets are a source producing spores and odour molecules into the warehouse air twenty-four hours a day. And the cardboard cartons sitting on top of them are the sponge that absorbs it.
The cost beyond the returned stock
The returned stock was 1.9 million baht. Khun Somchai says that number was only the starting point, because everything returned had to be repackaged: cartons and labour came to about 340,000 baht.
Roughly 15 percent of it had too little shelf life left to reship in time and had to be discounted or written off — another 280,000 baht.
But the heaviest cost was trust. One customer cut orders by 40 percent the following quarter and asked for a quarterly warehouse air quality report — a condition the business had never been asked for in twenty years.
He says what hurt most was that twenty years of a reputation for punctuality and quality was shaken by something he could not see and had never thought he needed to manage.
Three months of fixes that did not finish the job
The first step was repairing the roof and installing four powered extraction fans, at about 190,000 baht. That was the right thing to do and genuinely helps humidity in the long term.
Next, all wooden pallets were replaced with plastic ones for the affected product lines, at over three hundred thousand baht more, which did remove the main source.
But the musty smell in the warehouse remained, because years of accumulated spores and mould were not only on the pallets. They were on the walls, in the roof structure, in the racking, and in the warehouse air itself. Replacing pallets stops new production; it does not remove what already exists.
He tried a hundred bags of activated charcoal spread through the building — the most commonly recommended fix. It made no measurable difference at all, because charcoal adsorbs a very limited quantity of molecules that happen to pass it, in a space of 900 square metres with a seven-metre ceiling.
What it actually costs
Returned stock costs far more than the invoice value
1.9 million baht of returns was followed by 340,000 baht of repackaging and another 280,000 baht of stock with too little shelf life to reship. The real cost is always larger than the number on the return note.
Major customers cut orders immediately
In food distribution, trust is everything. One customer cut orders by 40 percent the following quarter and added a requirement for quarterly warehouse air quality reports — unheard of in twenty years of trading.
A food safety risk that auditors can see
Mould in warehouse air is not merely an odour issue. It is exactly what GMP and HACCP assessors look for. Fungal spores in a food storage area are a finding that can put a certification at risk.
Warehouse staff breathe that air eight hours a day
Pickers and forklift drivers are in the building all day. Continuous inhalation of fungal spores causes respiratory allergy, chronic cough, and in some cases hypersensitivity pneumonitis.
Why the usual fixes fail
Repairing the roof and adding extraction fans
Necessary and genuinely helpful for long-term humidity, but it does not remove the mould and spores already established on walls, roof structure, racking and in the air. Lowering humidity slows growth; it does not delete what exists.
Switching from wooden to plastic pallets
A worthwhile investment that removes the main source. But the spores those pallets released over several years have already settled on every surface in the building. Changing pallets stops new production; it does not clean up the old.
Charcoal bags spread through the warehouse
Charcoal adsorbs a very limited quantity of odour molecules that pass it. In 900 square metres with a seven-metre ceiling, the air volume is far too large for it to make a measurable difference, and it saturates within days.
Mopping floors and wiping racking with disinfectant
Surface cleaning works only where you can reach. The warehouse has a seven-metre ceiling, steel roof structure, high racking, and gaps between triple-stacked pallets that nobody wipes and nobody ever has.
Spraying disinfectant through the building
Chemical spraying in a food storage area is constrained by residue on packaging, and fogging also adds moisture to a warehouse that already has a humidity problem — feeding the very mould you are trying to remove.
A food warehouse needs a method that reaches every corner without residue and without adding moisture
A food warehouse imposes two hard constraints at once. First, the space is enormous with places no person can reach: a seven-metre roof structure, deep racking, stacked pallets. Second, no chemical residue is acceptable on food packaging.
Between them, those two constraints eliminate most methods. Wiping only reaches what you can touch. Chemical fogging leaves residue and adds moisture. Heat or steam is impossible at that scale with stock in place.
Ozone satisfies both. It is a gas, so it fills the entire air volume of the building — into the roof structure, the racking gaps, under the pallets and into the splits in the timber that nobody can reach. Where it meets mould, spores, bacteria or odour molecules, the third oxygen atom breaks away and oxidises them. Then the ozone decomposes back into ordinary oxygen, leaving no chemical residue on cartons or packaging, and adding no moisture whatsoever.
10 reasons ozone treatment solves it
1. It fills the entire air volume of the building
Ozone goes wherever air goes: the seven-metre roof structure, the gaps between racking, under triple-stacked pallets, and into splits in the timber — the areas nobody can reach and nobody has ever cleaned.
2. No chemical residue on food packaging
Ozone decomposes back into ordinary oxygen after reacting, so nothing is left on cartons, bags or food contact surfaces. This is the decisive advantage over chemical spraying in a food storage area.
3. It adds no moisture to a warehouse that already has a humidity problem
Fogging and washing add water to an already humid building, feeding mould directly. Ozone is a dry gas, so it does not dampen cardboard cartons and does not fuel the next growth cycle.
4. 99.99% removal of embedded mould
Testing confirms 99.99% removal of deep-seated mould in air conditioning systems and furnishings, with virus and bacteria kill an order of magnitude beyond that. For food storage, that is the level auditors want to see.
5. The Master Ozone Generator is certified by the Department of Medical Sciences
WHD uses the Master Ozone Generator, the only ozone brand in Thailand certified by the Department of Medical Sciences, Ministry of Public Health, and tested by Intertek UK — usable as supporting documentation for GMP audits and customer reports.
6. It treats the odour embedded in cartons and pallets at the same time
Corrugated board and timber are the most absorbent materials in the building. Ozone penetrates the porosity of both and breaks down the odour molecules held there, without replacing the cartons or discarding the pallets.
7. Stock does not have to be moved out
Ozone travels between stacks by itself, so there is no need to clear the warehouse, rent temporary storage, or halt operations for days — costs that are usually many times the service fee.
8. It can be done outside working hours
The automatic digital timer cycle runs about thirty minutes — two to start, twelve to disperse, twelve to purify, twelve to rest. The team works after hours and the warehouse is ready the next morning.
9. It reduces a real occupational health exposure
Pickers and forklift drivers breathe that air eight hours a day. Cutting the airborne spore load is a workplace safety measure, not only a product quality measure.
10. It gives you evidence you can send to customers
After an incident, customers want concrete measures. A documented ozone schedule with equipment certification from the Department of Medical Sciences is something tangible — unlike telling them you have increased cleaning.
Before and after
Before
- 1.9 million baht of stock returned by two customers because the cartons smelled musty
- 340,000 baht in repackaging and another 280,000 baht in stock discounted or written off
- A major customer cutting orders by 40 percent and demanding quarterly air quality reports
- Mould found on more than 400 wooden pallets and moisture accumulating in the roof structure
- 190,000 baht on roof repairs and fans plus over 300,000 baht on plastic pallets, with the smell still present
- A hundred bags of charcoal making no measurable difference
After
- No musty odour in the warehouse or in cartons stored after treatment
- No returns for odour reasons at all across the following nine months
- The customer who cut orders back to full volume by the second quarter
- Documentation usable for audits and quarterly customer reports
- Done outside working hours with no stock moved and not a single shipping day lost
- Warehouse staff reporting clearly less coughing and congestion during the rainy season
How we get you started, in 3 steps
Survey and assessment
The team measures the building's air volume, assesses ceiling height, racking layout, pallet stack positions and moisture accumulation points, then sets the number of machines, their positions and the number of cycles to cover the whole space.
Preparation and sealing
Surfaces with visible mould are disinfected first where needed. Doors and vents are sealed, gaps are opened between stacks as far as practical so the gas can penetrate, and everyone leaves the area.
Ozone cycle, ventilation and check
The machines run automatic cycles of about thirty minutes each; large spaces take several consecutive cycles. The building is then fully ventilated, surface moisture is checked, and the warehouse is ready the next morning.
What a customer says
“I had already spent nearly half a million on the roof and the pallets, which needed doing anyway, and the smell was still there — because ten years of accumulation was not only on the pallets. The team treated the whole warehouse on a Saturday night, and when I walked in on Monday it was a different building. What mattered even more was having documentation to send my customers showing what we actually do. We now treat quarterly.”
Khun Somchai K. — owner, dry food distribution business, Samut Sakhon
Why almost every warehouse in Thailand has a mould problem
Average relative humidity in Thailand runs 70 to 85 percent for most of the year, and in the rainy season some areas hold above 90 percent for weeks. Mould begins growing at around 65 percent. Thai warehouses therefore sit in mould-friendly conditions almost permanently.
Most warehouses use metal sheet roofing, which condenses on the underside overnight as temperatures drop. That condensation drips or seeps onto the structure and the topmost goods without anyone noticing.
The materials the logistics industry runs on are exactly what mould prefers: wooden pallets, corrugated cartons and layer boards. All organic, all moisture-absorbing, all direct food for fungi.
Combine that with ventilation that depends on turbine vents which stop working when the air is still, and the result is a large volume of stationary, humid, dark air, full of fungal nutrition, twenty-four hours a day.
What food businesses should do as a routine
The lesson Khun Somchai draws is that warehouse mould is not an event, it is a condition. It does not happen on one day; it accumulates until the day a customer tells you about it.
His current measures are four: control humidity by fixing leaks and installing powered extraction; use plastic pallets for odour-sensitive lines; ozone-treat the whole building quarterly as a routine; and keep the documentation every time for customers and auditors.
He stresses that the first two without the third are damage control, not improvement — because what has already accumulated has to be removed, not merely slowed.
For businesses undergoing GMP or HACCP audits, a documented ozone schedule with Department of Medical Sciences equipment certification is also direct evidence to an assessor that airborne contamination control is actually in place.
Frequently asked questions
How long does a 900 square metre warehouse take?
Large spaces need several consecutive cycles of about thirty minutes each, often with machines at multiple positions. It is normally completed within one night to one day, and the team assesses this at the survey.
Does stock have to be removed?
No. Ozone penetrates between stacks and racking by itself. We do recommend leaving gaps between stacks where practical so the gas distributes more evenly.
Is there residue on cartons or food packaging?
No. Ozone decomposes back into ordinary oxygen after reacting, leaving nothing on cartons, bags or food contact surfaces. This is the main reason food businesses choose it over chemical spraying.
Can it damage the stock?
No. Concentration and duration are controlled by the certified machine's digital timer, and sealed packaged goods are unaffected. The team advises on handling for any sensitive product categories at the survey stage.
How often should it be done?
For food warehouses in the Thai climate, quarterly as a routine, with increased frequency during the rainy season. A warehouse with long-standing accumulation should start with two or three consecutive treatments before moving to the routine schedule.
Does it work for cold rooms and freezers?
Yes. The team adjusts the cycle for the temperature and volume of the cold room — an area that commonly has mould and odour accumulation for the same reasons of humidity and sealing.
What certifications does the equipment hold?
WHD uses the Master Ozone Generator, the only ozone brand in Thailand certified by the Department of Medical Sciences, Ministry of Public Health, and tested by Intertek UK. Documentation is available for audit purposes.
Is anything included for large spaces?
For bookings of 15,000 baht and above, WHD includes free hospital-grade CHEMGENE HLD4H spray disinfection, certified by Mahidol University and NHS England — suited to contact surfaces in warehouses and packing rooms.
The product was fine. The air was not — and every carton carried it out of the building.
If your customers are starting to mention odour in goods that are within date and properly sealed, the problem is not the product. It is the air in your storage space, and it is being absorbed into every cardboard carton sitting in it.
Ozone treatment fills the entire air volume of the building, reaches the roof structure, the racking gaps and under the pallets that nobody can wipe, destroys the mould and spores at the source, leaves no chemical residue on food packaging, adds no moisture, and can be done outside working hours without moving stock.
For bookings of 15,000 baht or more, WHD includes free hospital-grade CHEMGENE HLD4H spray disinfection.
Warehouses, distribution centres, cold rooms, food factories, offices, hotels and homes across Thailand
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Call 065-556-6294 or add LINE @whd268
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