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

Day three after the water drops: the roller door goes up, and the smell hits you

Thana manages a mid-sized warehouse on the eastern side of Bangkok. He is standing in front of a wide roller shutter that he has just been able to open for the first time since the heavy rain of 24 to 27 September 2026. His building stores a mix of goods: tins of house paint, thinner, floor cleaners, bagged chemical fertiliser, lubricating oil, and ordinary consumer products in cardboard boxes stacked on wooden pallets. When the water started coming in, his team lifted only part of the stock onto racks. The rest sat in thirty to forty centimetres of water for several days.

The first thing everyone notices is not the collapsed boxes. It is a smell so mixed that nobody can name it: the sharp edge of solvent, an ammonia-like sting from split fertiliser sacks, motor oil, and the rotten-mud stench of floodwater that backed up from the drains. Two staff members who walk in first complain of stinging eyes and dizziness within minutes. Thana calls everyone out and starts thinking seriously about how to restore the building without making anyone ill, and how to make the odour trapped in the concrete floor, the walls and the racking actually disappear rather than simply be covered up.

Thana's situation is far from unusual. According to news reports, around 300 mm of rain fell in roughly 48 hours, flooding large parts of the capital, and on 26 September 2026 the Bangkok Metropolitan Administration declared all 50 districts a disaster zone. Eastern Bangkok was hit hardest, with areas such as Khlong Chan and Bueng Kum mentioned in coverage. Governor Chadchart said the canals were full and that drainage would take two to three days after the rain stopped. For any business with a warehouse in low-lying ground, those extra days of standing water are exactly what gives stored chemicals time to dissolve, soak in and spread.

Why flooded warehouses smell far worse than flooded homes

A typical home holds only small amounts of chemicals: washing-up liquid, floor cleaner, a few leftover paint tins. A warehouse concentrates many different chemicals in one place, in bulk. When floodwater arrives, the result is much more complicated.

1. Containers fail and labels disappear

Soaked cardboard collapses, toppling the bottles and jerry cans inside. Many caps are not designed to keep external water out. Sacks of fertiliser or powdered chemicals rot and burst. Paper labels peel away, so nobody knows what is in which container. Sorting becomes harder, and the risk of accidentally combining incompatible substances goes up.

2. Water carries the chemicals everywhere

Once a product leaks into standing water, that water carries it to everything submerged: pallets, steel rack legs, the lower walls and the slab. Substances that do not dissolve, such as oils and some solvents, float as a film and then stick along the high-water line as the level falls. That is why so many warehouses show a dark "bathtub ring" around walls and racking that smells particularly strong.

3. Porous materials soak it up and release it slowly

Unsealed concrete, rendered walls, timber pallets and insulation are all porous. Having absorbed contaminated water, they slowly give off volatile organic compounds (VOCs) for a long time, especially in the afternoon heat. This is why many managers find that even after every damaged item has gone, the smell creeps back every afternoon.

4. Sewage and decay add a second layer

Urban floodwater usually contains drain water and sewage. Combined with spoiled organic stock such as dry food, paper or textiles, it creates musty and putrid odours on top of the chemical smell. Mold and bacteria grow readily in damp conditions. The result is a layered odour problem that no single method fixes.

5. Warehouse ventilation was never designed for this

Many warehouses have few windows and rely on roller doors and roof fans. During the flood those doors stayed shut, so the air inside became warm and stale and vapour concentrations kept rising. The first opening is when the full force of it is felt.

Common sources of chemical odour in a post-flood warehouse

• Solvents and coatings such as thinner, lacquer, turpentine, oil-based paint and epoxy. These are a major VOC source and give a sharp, headache-inducing smell.
• Fuels and lubricants from forklifts, storage tanks or stocked engine oil, leaving a persistent oily smell and greasy film.
• Fertilisers and agricultural chemicals. Some fertilisers smell of ammonia when wet; pesticides should always be treated as hazardous and handled according to their safety data sheets.
• Cleaning agents and bleach. Chlorine-based or acidic products that leak and mix in water can give off pungent, irritating gases.
• Plastics, rubber and packaging that have been soaked and then heated, adding plastic or rubber smells.
• Rotting organic material, adding musty, sour and sulphurous notes.

Important: if your warehouse stores hazardous or flammable chemicals, or containers are still leaking, the first step must be a safety assessment by the person responsible for safety in your company, using each product's safety data sheet (SDS), and contacting the relevant authorities or licensed chemical and waste specialists as required by law. Ozone treatment is not a method for dealing with an active liquid or powder spill, and it is not hazardous waste disposal. Its role comes later, once leaked material and contaminated items have been removed, to deal with the odours and vapours left behind.

How chemical odours and VOCs affect the people who work there

A chemical smell is more than a nuisance. It tells you molecules of something are floating in the air you breathe. Effects depend on the substance, the concentration and how long people are exposed. Workers in enclosed spaces with built-up vapours commonly report:

• stinging or watering eyes, irritated nose and throat, coughing;
• headache, dizziness, nausea, fatigue and poor concentration;
• shortness of breath or chest tightness, especially in people with asthma or allergies;
• skin irritation or rashes after direct contact with contaminated water or residue.

Who needs extra care

Staff with asthma, allergies, chronic lung disease or heart conditions, pregnant employees, older workers, and anyone who will spend long shifts inside should stay out of a warehouse that still smells strongly of chemicals. Managers should bring these groups back last, or assign them elsewhere first.

Flood-related infection risks on top

Floodwater also brings germs. People wading through water or mud to move stock are at risk of leptospirosis, skin infections and diarrhoeal illness. Anyone who develops a high fever, muscle pain (especially in the calves), red eyes, diarrhoea or breathing difficulty after entering the area should see a doctor promptly and mention flood or chemical exposure. No odour-removal service is medical treatment.

News reports noted three deaths in this flood, including an electrocution in a car park. It is a sobering reminder to have an electrician inspect and isolate flooded circuits before anyone enters a building that has been underwater. Our condolences go to the families affected.

What a lingering chemical smell costs a business

Staff health and morale

Working in a building that still smells pungent leads to fatigue, headaches, more sick days and a feeling that the company does not take safety seriously. That loss of confidence affects productivity and staff turnover long after the water is gone.

Stock and customers

Goods that never touched the water but share the same air, such as textiles, paper, packaged dry food or items with plastic parts, can absorb the odour. A customer who opens a box and smells solvent will return it and lose trust. The damage spreads from the stock that sank to the stock that looked safe.

Time and money

Every day the warehouse is out of action means late orders, temporary storage costs, wages paid without output and sometimes contractual penalties. One Thai business report cited a Chamber of Commerce estimate of about 12,300 million baht in damage from this flood; part of that is the cost businesses carry while waiting to get their workspace back.

Reputation and audits

Visiting partners, standards auditors and insurance assessors all notice the smell immediately. A warehouse that still reeks of chemicals signals poor control. Air-quality measurements taken before and after recovery are a strong way to show the problem was handled properly.

Employees' families

Many employees in eastern Bangkok had their own homes flooded too. They are fixing home and workplace at the same time. Going home every day with clothes smelling of chemicals and a headache adds stress for them and for the people they live with. Making the workplace safe quickly is a way of caring for the whole team.

Why the usual fixes do not make the smell go away

Open the doors and run industrial fans

Ventilation is essential and helps a lot at first. But fans move air; they do not reach the chemicals locked in porous concrete, pallets and walls. Close the doors overnight and vapours build up again, so the smell is back by morning.

Pour on strong bleach

Where several chemicals are already mixed together, adding concentrated chlorine can react with some of them, for example ammonia-containing or acidic products, and create more irritating gases. Cleaning should use suitable products, according to the label, and never mix chemicals.

Air fresheners and odour blocks

Fresheners only add a fragrance on top, and some contain VOCs themselves. The original smell remains, with a new one layered over it, and headaches get worse. Activated carbon helps in small rooms, but for a warehouse of several hundred square metres the quantity and time needed are unrealistic.

Paint over it or re-coat the floor right away

If surfaces are still damp and contaminated, new paint peels, mold grows underneath, and fresh paint and coatings add a second batch of VOCs to the air. You end up with two layers of chemical smell.

Wait for it to fade

Odours do fade naturally, but from deep inside porous materials it can take weeks or months. Meanwhile staff are working and stock is moving, and nobody knows whether the air is acceptable because nothing is being measured.

The targeted answer: WHD ozone chemical-odour and residue removal

World Health Disinfection (WHD) offers an ozone service for chemical odour and residue removal that fits the final stage of warehouse recovery, once damaged stock is out and the space is washed and dry. According to the service information, ozone (O3) breaks odour molecules down at the source instead of masking them. It targets paint, thinner, epoxy and lacquer odours, VOCs and musty smells, and also helps against bacteria, viruses and mold. Afterwards it reverts to oxygen with no residue.

Why ozone suits big spaces like warehouses

Ozone is a gas, so it travels wherever air goes: between high racks, under pallets, above ceilings and into corners no cloth can reach. Liquid spraying, by contrast, depends on someone walking to every spot. For large air volumes, WHD uses the Master Ozone Generator and plans the number and placement of units around the real dimensions of the space.

Measured results, not just "it smells better"

What warehouse managers value most is measurement. According to the service information, WHD measures TVOC (total volatile organic compounds) with calibrated instruments before and after treatment, giving you numbers you can report to management, partners or your insurer.

How the job runs in a warehouse

1. Survey and assessment. The team inspects the site, asks what goods and chemicals were stored, confirms leaked materials and damaged containers have been removed, and checks there are no open vapour sources.
2. Baseline TVOC. Readings are taken at several points: where paint and solvents were stored, along the highest water line, and in any office area inside.
3. Preparation. All people, pets and plants leave. Doors and windows are closed, unnecessary openings sealed and "no entry" signs posted.
4. Ozone release. The Master Ozone Generator runs in the empty, closed space for the time planned for that volume and odour level.
5. Contact and rest. Ozone works on the odour molecules, then the space rests and is ventilated. According to the service information, it is ready to use about two hours after treatment.
6. Follow-up TVOC. Readings are repeated at the same points and compared, and any area needing a repeat or further source removal is identified.

Safety first: ozone treatment is carried out only in an empty, closed space. People, pets and plants must be out, and may re-enter only after the rest and ventilation period. Ozone comes after mud removal, washing and drying. It does not replace cleaning, legally required hazardous chemical handling, or medical care.

10 reasons businesses choose ozone for post-flood warehouse chemical odours

1. It works on the source, not as a mask. Ozone breaks odour molecules apart, as described on the chemical residue ozone service page.
2. It reaches the top of high racking and the gaps behind pallets that no cloth reaches.
3. No new chemical layer. Ozone reverts to oxygen, adding no new smell or film to stock you bring back.
4. Several odours in one pass: solvent, oil, mustiness and rotten mud together.
5. Helps reduce microbes in air and on surfaces; the service information lists bacteria, viruses and mold.
6. Before-and-after TVOC numbers to support management reports, partner visits and insurance claims.
7. Fast return to use: about two hours after treatment, cutting downtime.
8. Professional equipment: the Master Ozone Generator, sized to your actual volume. See the WHD service details.
9. Fits your renovation plan. If you repaint or re-coat the floor, a second treatment can tackle new paint and epoxy odours.
10. Restores staff confidence. Workers see the company cares about the air, not just about reopening. Talk to the team.

Before and after: what the right sequence changes

Example case: a building-materials store room in eastern Bangkok

Example case (an illustrative scenario explaining the process, not a specific customer's testimonial)

Malee owns a building-materials shop with a store room behind it. In late September 2026 it stood in shin-deep water for several days. Inside were oil paints, thinner, waterproofing compound, contact adhesive and bagged ready-mix mortar. When the water went down she found several thinner cans tipped over with their caps off, mortar bags set hard, and a thin oily film across the whole floor.

She first had an electrician check the wiring before switching anything on. Her team, wearing gloves, boots and suitable masks, moved leaking containers to a safe open area, called a licensed waste contractor for spoiled paint and solvent, and removed the mortar bags and wet cardboard. They washed the floor with a degreaser used according to its label, without mixing products, and ran fans for several days to dry it out.

Even with a dry, clean-looking floor, solvent and musty smells lingered, strongest where the thinner had been stored. She contacted WHD. The team took baseline TVOC readings at several points, cleared everyone out, sealed the room and ran a Master Ozone Generator, then rested and ventilated the space before re-measuring at the same points. In her account, the smell that had been giving staff headaches dropped enough for them to restock as normal, and she had figures to show the insurance assessor.

The lesson: ozone performs best at the right moment, after the source has gone. Run it with open thinner cans still on the floor and the smell will simply keep being released.

Warehouse recovery checklist: before and after ozone

Stage 1: Safety before entry

• Wait for the water to recede; have an electrician inspect and isolate flooded circuits.
• Open doors from outside and air the space before anyone goes in.
• No smoking or open flames if flammable vapours are suspected.
• Provide chemical-resistant gloves, boots, safety glasses and masks suited to the substances.
• Keep high-risk staff, such as pregnant or asthmatic employees, outside.

Stage 2: Sort and handle leaked chemicals

• Check the stock list against each product's safety data sheet.
• Isolate leaking, unlabelled or unknown containers; never pour them together.
• Use a licensed contractor for spoiled chemicals and contaminated materials.
• Photograph and record damage for insurance.

Stage 3: Remove mud, wash and dry

• Remove mud, wet cardboard, rotten pallets and anything that has soaked up chemicals.
• Wash floors and walls with suitable products per the label; scrub the oily high-water line.
• Dry with fans and ventilation. Public-health agencies such as the CDC advise cleaning and drying within 24 to 48 hours to limit mold.
• To disinfect washed surfaces, consider a medical-grade disinfectant such as Chemgene HLD4H, at the label dilution and contact time.

Stage 4: Ozone for residual odour

• Confirm no open or leaking chemical containers remain.
• Take baseline TVOC readings.
• Remove all people, pets and plants; seal the space; post signs.
• Treat, rest, ventilate, then take follow-up TVOC readings.

Stage 5: After treatment

• Re-enter only after the rest and ventilation period the team specifies.
• If repainting or re-coating, plan a second treatment once the work has cured.
• Redesign storage: chemicals above the previous flood line, incompatible products separated.
• Watch staff for symptoms in the first week back; anyone unwell should see a doctor.

FAQ: chemical smells in flooded warehouses

Can we run ozone while spilled chemicals are still on the floor?

No. Leaked material, damaged containers and contaminated items must be removed and handled lawfully first. Ozone is for the odours and vapours left once the source is gone.

Can staff keep working during treatment?

No. Ozone treatment happens in an empty, closed space with all people, pets and plants out. Re-entry is only after the rest and ventilation period; according to the service information the space is ready about two hours after treatment.

How do we know the smell really dropped and our noses did not just get used to it?

WHD measures TVOC with calibrated instruments before and after, at the same points, so the change is shown in numbers rather than impressions.

What about stock that stayed dry but now smells?

It depends on the product. Sealed items may only need their outer packaging cleaned, but anything related to food, medicine or skin contact should be discussed with the manufacturer, with consumer safety first. Odour treatment is never a reason to sell goods that may be contaminated.

Should we treat before or after repainting or epoxy flooring?

Many sites do both: once after washing and drying for flood odours, and again after the new paint or epoxy has cured, to reduce fresh VOCs. According to the service information, ozone handles paint, thinner, epoxy and lacquer odours.

Can ozone damage stock or the building?

The team assesses the site and advises what to remove or protect. Sensitive or high-value goods are generally moved out during treatment, and the run time is matched to the space.

A worker has sore eyes and a headache after going in. What now?

Move them to fresh air. If symptoms persist, or they have breathing trouble, fever, calf pain or diarrhoea after wading, they should see a doctor promptly and describe their exposure. Ozone treatment improves the environment; it is not a treatment for people.

Still smelling chemicals in your warehouse after the flood? Talk to WHD today

Site assessment, before-and-after TVOC measurement and an ozone plan sized to your warehouse.

Get advice on ozone chemical-odour removal

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

Related services

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

References

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