A typical scenario (an illustrative situation drawn from common post-flood experiences, not a review from any specific customer)

The "Open" sign was up, but the first customer left within ten seconds

Tom runs a mid-sized furniture and home-decor showroom in Bueng Kum, on the ground floor of three shophouse units knocked together into one long space. The front is a wall of glass showing fabric sofas, teak dining sets and hand-woven rugs; the back holds a stockroom and a small office corner. In late September 2026, days of heavy rain flooded Bangkok, and according to news reports the eastern side of the city was hit hardest. Water pushed in under the roller shutter, rose to mid-shin across the floor and sat there for days while the drainage system struggled to catch up.

When the water finally drained, Tom's team of five shovelled out the mud, dragged the soaked sofas onto the pavement, hosed down the tiles, scrubbed table legs and wiped every display cabinet with a lemon-scented cleaner. Because a brown tide line ran along the lower walls, they repainted the whole band. A contractor re-coated the laminate in the display corner and put fresh lacquer on a few slightly swollen timber shelves. Within a week the store looked as good as ever, so Tom hung the "Open" sign again, hoping to recover almost two weeks of lost sales.

The first customers that morning were a couple shopping for a sofa for their new home. They pushed open the glass door, paused, and the wife lifted a hand to her nose without thinking. "It smells like a drain mixed with paint," she said quietly, smiled politely and asked to come back another time. Tom could not smell a thing, because he had been inside all day and his nose had adapted. Anyone walking in from the street, however, got the full blend within seconds, and those first seconds decide whether a shopper stays or goes.

Clothing boutiques, car and motorcycle showrooms, phone stores, pharmacies and cafés in flooded shophouses face the same challenge: the shop floor is clean, but the air is not ready for customers. This article explains where those odours come from, why the usual quick fixes fall short, and how ozone odour and chemical-residue removal fits in as the final step before you reopen.

The late-September 2026 Bangkok floods and ground-floor retail

According to news reports, roughly 300 mm of rain fell over about 48 hours between 24 and 27 September 2026, flooding large parts of Bangkok. On 26 September the Bangkok Metropolitan Administration declared all 50 districts a disaster zone. Eastern Bangkok suffered most, with areas such as Khlong Chan and Bueng Kum frequently mentioned. Governor Chadchart said the canals were full and that drainage would take two to three days after the rain stopped. As of 30 September, some roads, including Si Burapha and Lat Phrao, still had 20 to 40 cm of standing water.

Thai media compared the event with the 2011 floods, and one Thai business report cited a Chamber of Commerce estimate of about 12,300 million baht in damage. Behind that figure are thousands of small business owners who had to close temporarily, and whose top priority now is to reopen quickly without losing customer confidence.

Shops and showrooms have features that make post-flood odours far more stubborn than in a typical home. Most sit at street level, so the water that came in was road runoff mixed with drain water, engine oil and rubbish. They are full of materials that soak up smells: upholstery, curtains, clothing on racks, rugs, cardboard boxes in the stockroom and gypsum ceiling boards. They usually stay shuttered overnight and air-conditioned during the day, so the same air recirculates in a closed box. And they tend to renovate in a rush, repainting, re-lacquering, installing new counters and receiving new stock all at once, so chemical odours from the renovation pile on top of the original flood smell.

Where post-flood shop odours come from

Owners often lump everything together as "flood smell," but what a customer actually breathes is a mixture from several sources, each with a different cause and a different fix.

1. Mud and sewage

Urban floodwater is not clean rainwater. It has passed through drains, manholes and road surfaces, carrying rotting organic matter and waste. When that sediment lodges in tile grout, under display cabinets, behind counters and inside fabrics, bacteria keep breaking it down and releasing foul-smelling gases. Even after the floor looks clean, the smell can return whenever the temperature or humidity rises.

2. Musty odours from damp and mold

Masonry walls that sat in water for days hold moisture for weeks. Gypsum ceilings that wicked water upward, plywood cabinet backs and cardboard stock boxes are ideal food for mold. Health agencies such as the CDC and WHO advise cleaning and drying within 24 to 48 hours to limit mold growth, but when water stands for days, most shops simply cannot meet that window. The "old storeroom" smell often starts before the water even recedes.

3. Fuel and oil

Water flowing along main roads often carries oil from stalled or submerged vehicles. Car and motorcycle showrooms and service centres may also have engine oil, gear oil and fuel leaking from their own vehicles if water reaches engine bays. These smells sink into floor grout and lower walls and can make people feel light-headed after long exposure.

4. Cleaning-chemical smells

After a flood, shops typically use far more bleach, toilet cleaner, strongly scented floor cleaner and air freshener than usual, partly to feel clean and partly to mask the mud smell. The result is a cloud of chlorine and synthetic fragrance trapped in a closed space. Some customers, especially those with allergies or asthma, experience stinging eyes or noses.

5. Paint, thinner, epoxy and lacquer from renovation

This is the source owners most often overlook, because a paint smell feels like the smell of "something new." In reality oil-based paint, thinner, lacquer, epoxy floor coatings, carpet and laminate adhesives, and engineered wood in new fixtures all release volatile organic compounds (VOCs) for days or weeks. When a shop repaints, re-coats its floor and receives new display furniture within a few days, indoor VOC levels can climb well above normal, and a sealed, air-conditioned store lets them accumulate.

6. Odours absorbed into stock

For shops selling textiles, leather, paper or wood, the problem is not only in the air. The merchandise itself absorbs odour. Clothes that never touched the water can still pick up mustiness from hanging in a humid store for days. Leather shoes, bags and packaging are the same. A customer who opens a shopping bag at home and smells mildew is unlikely to return.

Who is affected by odours and VOCs in a shop

Odour is not just about comfort. Some VOCs at high concentrations can irritate the eyes, nose and throat and cause headaches, nausea or dizziness, while mold spores and musty air are well-known triggers for allergies and asthma. People who deserve extra care include:

• Sales staff and cashiers, who spend eight to ten hours a day inside, every day, and receive far more exposure than any shopper.
• Older customers, who often browse slowly, for example in furniture or appliance stores.
• Young children, who breathe faster than adults and are closer to the floor, where heavier odours collect.
• Pregnant women, who are often sensitive to smells and are generally advised to avoid breathing paint and solvent fumes.
• People with chronic conditions such as allergies, asthma or chronic lung disease, whose symptoms can flare in damp, moldy or dusty spaces.

One point needs to be clear: if any employee who helped clean up the shop develops fever, muscle pain (especially in the calves), red eyes, diarrhoea or other unusual symptoms after wading through floodwater, they should see a doctor right away and mention the flood exposure. These can be signs of flood-related illness such as leptospirosis. Ozone treatment and cleaning are not medical treatment and cannot replace medical care.

What lingering odour really costs a retail business

Sales lost at the door

Every retail format relies on the first few seconds after a customer walks in. A drain or mildew smell is a negative signal the brain processes almost instantly. Shoppers may not say a word, but they browse less, touch fewer products and leave sooner, which quietly reduces sales without the owner ever knowing why.

Online reputation

Customers can post a review on a map listing or social media within minutes. A rating built over years can slip simply because the shop reopened before the air was dealt with.

Unsellable or returned stock

Merchandise that has absorbed odour may need to be discounted, re-laundered or accepted back as returns, all of which add cost. In a car showroom, a smell can make customers wonder whether the vehicles on display were flooded, even if they were not affected at all. A small doubt like that has a big effect on a high-value purchase.

Why the usual quick fixes don't fully work

Air freshener and reed diffusers. These mask odour rather than remove it. The original odour molecules remain, and a layer of synthetic fragrance is added on top. When the scent fades by mid-afternoon, the mustiness returns, and many customers find perfume-plus-mildew worse than mildew alone.

Bleach on everything. Bleach is useful for hard surfaces when used correctly, but it cannot reach odours suspended in the air, trapped in fabric or hidden above the ceiling. It adds a chlorine smell, and mixing it carelessly with other cleaners can create dangerous gases.

Fans and an open shutter. Ventilation genuinely helps and should be done. But in a shophouse with only one open side, the back of the store, the stockroom and dead corners barely exchange air. While the street outside still has standing water or drying mud turning to dust, an open door can also pull more odour and dirt inside.

Painting over water stains. Fresh paint makes walls look clean, but if the wall is not fully dry the paint traps moisture inside, mold continues to grow underneath, and the new paint smell layers on top of the old mustiness. That is exactly the "drain mixed with paint" smell in the story above.

Waiting it out. Paint and renovation VOCs do decline over time, but that can take weeks, and musty odours may never go away while the source remains. Most shops cannot afford to wait weeks.

WHD ozone odour and chemical-residue removal: the final step before reopening

World Health Disinfection (WHD) provides ozone chemical-residue and odour removal for homes, condos, offices, factories, construction sites, hotels, storage facilities and vehicles, which includes shops and showrooms recovering from flooding. According to the service information, ozone (O3) oxidises odour molecules directly, breaking them apart at the source rather than covering them up with fragrance.

According to the service information, ozone targets paint, thinner, epoxy and lacquer odours, VOCs and musty smells, and also helps reduce bacteria, viruses and mold in the air and on surfaces. After the contact time, ozone reverts to oxygen and leaves no residue, and the space is ready to use about 2 hours after treatment. That makes it well suited to shops that need to reopen fast: treatment can be scheduled overnight or on a closing day, and trading can resume the next morning.

What sets the service apart is measurement. WHD measures TVOC (total volatile organic compounds) with calibrated instruments before and after treatment, so you do not have to rely on your own nose, which has long since adapted. You get numbers you can compare. The team uses a Master Ozone Generator designed for larger spaces.

How the process works for shops and showrooms

1. Site survey. The team reviews floor area, ceiling height, stockroom, toilets, staff room and air-conditioning, and identifies the main odour sources such as freshly painted walls, newly coated floors or corners where mud collected.
2. Baseline TVOC measurement. Readings are taken at several points to compare with results after treatment.
3. Preparation with the owner. Plants, animals (aquarium fish, the shop cat) and any items the team identifies as sensitive to oxidation are removed. Cabinets, drawers and internal doors are opened so ozone can reach every corner.
4. Sealed and empty. Ozone treatment is carried out only in an empty, closed space. All people, pets and plants must be out. Warning signs go on the door so no one enters by mistake.
5. Ozone release and contact time. The Master Ozone Generator releases ozone at a concentration and duration matched to the space and odour level.
6. Rest and ventilation. The space rests while ozone reverts to oxygen. No one re-enters until the team confirms the period is complete.
7. Post-treatment TVOC measurement. Readings are compared with the baseline and explained to the owner, with advice on keeping the air fresh afterwards.

It is important to be clear from the start: ozone treatment comes after mud removal, washing and drying; it does not replace them. If wet mud remains under a cabinet or a wall is still saturated, those sources will keep producing new odour and ozone will only help temporarily. The service helps reduce odour and chemical exposure during recovery; it does not prevent flooding and is not medical treatment.

10 reasons shops and showrooms should ozone-treat before reopening

1. Customers smell before they see. Ozone odour removal for your shop turns that first impression positive from the moment the door opens.
2. It removes odour rather than masking it. Ozone breaks odour molecules at the source, so you do not need heavy fragrance that some customers dislike.
3. One treatment covers flood and renovation odours. Mustiness, sewage, paint, thinner, lacquer and epoxy smells are addressed together.
4. It helps lower VOCs. Staff who spend all day inside breathe more comfortably, with fewer headaches and less irritation.
5. Before/after TVOC numbers. Results come from calibrated instruments, not guesswork, and can be shared with your landlord or franchisor.
6. No residue on merchandise. Ozone reverts to oxygen, leaving no film on clothes, furniture or packaging.
7. It reaches where hands can't. As a gas it penetrates behind cabinets, under counters, between hanging garments and into stockrooms.
8. Ready in about 2 hours after treatment. Treat after closing and open as normal; no extra lost trading days.
9. It helps reduce airborne bacteria, viruses and mold. Extra hygiene confidence after sewage-contaminated floodwater.
10. A professional team with a Master Ozone Generator. Suitable for large stores and high-ceiling showrooms. See details on the ozone chemical-odour removal service page.

Before and after ozone treatment in a shop

Note: results depend on the size of the space, the starting odour level and how thoroughly the space was cleaned and dried beforehand.

Example case: a motorcycle showroom on a main road in eastern Bangkok

Example case (a simulated scenario to illustrate the process, not a testimonial from a real customer)

Em manages a motorcycle showroom with a small service bay on a main road in eastern Bangkok. Floodwater rose high enough to cover the wheels of the display bikes and flowed into the workshop at the back, where old engine-oil drums and spare parts were stored. After the water receded, the mechanics moved every bike out for inspection, cleared the mud, washed the floor with an oil-removing degreaser and ran industrial fans for days. Then painters redid the showroom walls, and the workshop floor got a fresh epoxy coat over the old, peeling one.

The problem was a faint oil smell mixed with epoxy and fresh paint that hung over the whole showroom. Some customers asked directly whether the bikes had been underwater, which hit confidence hard. Em contacted WHD for a survey. The team took baseline TVOC readings at the front, the middle and the workshop, and found the newly coated workshop highest. They planned a separate treatment for the workshop once the epoxy had cured for the period specified by the manufacturer.

On the scheduled day the showroom closed early, every employee left the building, the shutter came down, warning signs went up and treatment proceeded. After the rest and ventilation period, the team re-measured TVOC and walked Em through the comparison. Em could then use the readings, with each bike's inspection report, to reassure customers.

The lesson is that order matters: remove mud, wash, dry, repair, let new materials cure, and only then ozone-treat as the last step before reopening. Treating before the painters finish means treating twice, because paint applied afterwards releases new VOCs.

Checklist for reopening a shop after a flood

Before booking ozone treatment

• Have a qualified electrician check the system before switching breakers on, especially low sockets and distribution boards. Never switch on power while water remains inside.
• Wear rubber gloves, boots and a mask when shovelling mud and washing floors; wash hands after every session.
• Remove all mud, including under cabinets, behind counters and in shutter tracks.
• Separate flooded stock from unaffected stock and photograph everything for insurance.
• Discard saturated materials not worth saving, such as sagging gypsum ceiling, insulation and rugs soaked in sewage water for days.
• Clean hard surfaces, then disinfect with a suitable product such as Chemgene HLD4H medical-grade disinfectant at the label dilution and contact time.
• Dry with fans and dehumidifiers; open lower wall panels or ceiling sections to check hidden moisture if needed.
• Finish repairs, painting, floor coating and new fixtures, and let materials dry or cure per manufacturer guidance.
• Clean or replace air-conditioner filters that may have pulled in odour and mud dust.

On treatment day

• Remove all people, pets, plants and aquariums.
• Open cabinets, drawers, stockroom and staff-room doors so ozone circulates fully.
• Switch off air-conditioning as advised and seal openings into neighbouring units.
• Stay out during treatment and the rest period until the team says it is safe.

After treatment

• Ventilate as advised, then run air-conditioning normally.
• Check former hot spots. A localised smell that persists may point to hidden moisture worth investigating.
• Keep humidity low and watch wall corners for mold over the following weeks.

FAQ: ozone treatment for shops and showrooms after a flood

How long does the shop need to close?

It depends on the area and odour level. According to the service information, the space is ready about 2 hours after treatment, so most shops book after closing or on a day off and open as usual the next day. The team confirms total timing after the survey.

Do I need to remove all merchandise?

No. General stock can stay in place, but plants, animals and certain items sensitive to oxidation should be removed as the team advises during the survey.

Should I treat before or after repainting?

After. Wait until painting, floor coating and new fixtures are complete and materials have dried or cured as the manufacturer recommends; treating first will not address paint odours that appear later.

Can ozone replace cleaning and disinfecting?

No. Ozone comes after mud removal, washing, surface disinfection and drying. Skipping those steps leaves odour sources and germs that let the smell return.

How do I know the air really improved?

WHD measures TVOC with calibrated instruments before and after treatment, so you see comparable numbers instead of relying on smell alone.

A staff member feels unwell after the clean-up. What should we do?

If they have fever, calf pain, red eyes, diarrhoea or other unusual symptoms after flood exposure, they should see a doctor promptly and mention it. Ozone treatment is not medical treatment.

Reopen to the smell of a fresh store, not a flood

Let WHD survey your space, measure TVOC and schedule ozone treatment at a time that does not disrupt your trading.

Book a Survey and Ozone Treatment for Your Shop

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

Related links

• Ozone chemical-residue and odour removal service
• 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