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

Year-end is coming, and the client archive boxes are covered in black spots

Wipa is a partner in a small accounting firm in a three-storey commercial building off Lat Phrao. Her team of ten handles bookkeeping, tax and payroll for dozens of small and medium-sized businesses. The ground floor has a client reception area at the front and a file room at the back, lined with steel shelving almost to the ceiling. On the shelves sit hundreds of corrugated archive boxes, labelled by client and financial year, holding payment vouchers, tax invoices, copies of tax filings, ledgers and contracts the firm keeps on its clients' behalf.

From 24 to 27 September 2026 the rain was relentless. According to news reports, around 300 mm fell in roughly 48 hours. On the worst evening the team rushed computers and current-year boxes upstairs, but several years of older boxes on the bottom shelves could not be moved in time. Water about a hand-span deep entered the file room and stayed for days. News reports said Lat Phrao Road still had 20 to 40 cm of standing water as late as 30 September.

When they could finally get back in, the bottom-row boxes had collapsed. Water had wicked up the cardboard well above the actual waterline. Papers inside were stuck together in blocks, and some ink had run. Boxes on the second and third shelves looked fine, but when Wipa lifted a lid, a damp, musty smell hit her immediately. Grey and black mold spots dotted the edges of the binders. That night, a colleague with allergies could not stop sneezing after an afternoon of carrying boxes.

The hardest part was not the damaged paper. It was the responsibility to clients. These documents are the accounting and tax evidence of other people's businesses, and many are originals needed in an audit. Wipa had to work out which documents were damaged, which could be saved, and whether the room was safe to keep using, both for the paper and for the lungs of the team who go in and out every day.

This scenario is playing out at accounting firms, law offices and other professional practices after the Bangkok floods of late September 2026. This article explains why file rooms are places where mold spreads quietly, the right order for recovering documents and the room, and where ozone disinfection fits as the final step.

The 2026 Bangkok floods and practices that store files on the ground floor

According to news reports, the Bangkok Metropolitan Administration declared all 50 districts a disaster zone on 26 September 2026 after continuous heavy rain. Eastern Bangkok was hit hardest, with Khlong Chan and Bueng Kum among the areas mentioned. Governor Chadchart said canals were full and drainage would take two to three days after the rain stopped. 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.

Many small and mid-sized accounting and law firms operate from commercial buildings or shophouses, and they tend to keep files on the ground floor. Paper boxes are heavy, carrying them up stairs is hard, and ground floors take the weight of steel shelving better. Some firms in taller buildings use basement rooms or storerooms near the car park, which also flood first. File rooms usually have no windows and little airflow, and the air conditioning runs only during office hours. When power is cut or the office closes for days during a flood, humidity in the room climbs fast.

Mold in a file room: why paper is such good food

Paper, corrugated boxes, card binder covers and bookbinding glue are all made of plant fibres and starch, which mold feeds on directly. With high humidity and Bangkok heat, mold spores that are always present in the air can germinate and grow within days. WHO and the US CDC advise cleaning and drying within roughly 24 to 48 hours to limit mold. Tightly packed boxes and binders dry very slowly, so moisture stays inside long after the outside looks dry.

Documents that sat in floodwater carry an extra layer of risk. Urban floodwater runs through drains and sumps, carrying faecal bacteria, viruses, rat urine that may carry leptospirosis, and silt. These papers should never be handled bare-handed.

Hot spots specific to accounting and law firm file rooms

• Bottom-row corrugated boxes wick water far above the waterline and sag until the boxes above tilt.
• Lever-arch files and ring binders with card covers wrapped in plastic hold moisture inside the cover for a long time.
• Ledgers and bound documents, where spine glue and stitching absorb moisture and mold starts at the spine.
• Steel shelving and mobile compactor units, with floor rails where mud and water linger and gaps between units where air barely moves.
• Wooden cabinets and filing drawers made of plywood or particleboard that soak up water and swell.
• Carpets and ceiling panels in reception or meeting rooms next to the file room.
• Air conditioning that carries file-room air into the team's workspace.

Symptoms the team should watch for

Opening moldy boxes, flipping through binders or brushing paper in a closed room lifts spores straight to breathing height. That can cause sneezing, a blocked or runny nose, irritated eyes and throat, coughing, itchy rashes or asthma attacks. Anyone who waded in to move files and then develops fever, headache, muscle pain (especially in the calves), red eyes or diarrhoea must see a doctor promptly and mention the flood exposure. Thailand's Department of Disease Control regularly warns about leptospirosis after floods, and disinfecting a room is not medical treatment.

Who is most at risk

Accountants, clerks and paralegals who pull files every day have the most continuous exposure, especially those with allergies or asthma, pregnant staff, older colleagues such as senior partners or consultants who still work, and anyone with chronic illness or weakened immunity. Clients meeting in a reception room that shares air conditioning with the file room may also be affected.

The impacts professional firms have to manage

Health. A moldy file room releases spores continuously. Staff may develop lingering allergy symptoms without knowing the cause, and that affects concentration in detail-heavy work like accounting and law.

Responsibility to clients. Files are not just the firm's property; they are clients' evidence. Some documents must be retained as required by law, so damage has to be recorded, reported to clients and handled systematically. Consult your auditor, a lawyer or the relevant authority about what to do with damaged records.

Money and time. Recovering documents, rescanning, requesting copies from clients or agencies and rebuilding the filing system takes many hours, especially when the flood lands during client deadlines. Every hour spent on recovery is an hour not billed.

Reputation. Accounting and law firms sell trustworthiness. A client who walks in and smells damp, or receives documents back with mold spots, may wonder whether the firm takes proper care of their sensitive information.

People. Staff working in a musty room with flaring allergies may take more sick days or start looking elsewhere. Looking after workplace air is also about keeping good people.

Why the usual office responses fall short

1. Turning the air conditioning down hard. AC removes some humidity but kills nothing, and if the system itself is damp it can circulate spores to the whole floor.

2. Brushing mold off boxes in the same room. Brushing or wiping in a closed room lifts spores that settle on other boxes. It spreads the problem rather than solving it.

3. Spraying alcohol or disinfectant onto documents. Re-wetting paper can make ink run and worsen damage, and some products leave marks on important records.

4. Scent sachets and odour gels. Fragrance masks the smell but does not reduce mold, and it makes a growing problem harder to notice.

5. Putting dry-looking boxes straight back. If walls, floor, compactor rails and air still carry mold, boxes that look fine can develop it later.

The common thread: firms focus on documents box by box, but the room and its air are what those documents will live with for years.

WHD ozone disinfection for office file rooms

Ozone (O₃) is a strongly oxidising gas. In a closed room it spreads through gaps between steel shelves, between compactor units, behind boxes and through the air, breaking down the cell structures of bacteria and mold and the outer layers of viruses, and breaking musty odour molecules apart at the source. It then reverts to oxygen (O₂), leaving no chemical residue on shelves or surfaces, and no liquid needs to be sprayed onto documents.

According to the company's certified test results, World Health Disinfection (WHD) ozone treatment has been tested by Thailand's Department of Medical Sciences and Intertek (UK), eliminating viruses, bacteria and mold by 99.99% under test conditions. More on the residential and building ozone disinfection service page.

Key principles before work starts

• The room must be empty of people, pets and plants. During treatment the file room and any connected zones are sealed with nobody inside. People return only after the rest and ventilation period the team specifies.
• Recover documents and dry the room first. Ozone comes after mud removal, washing floors and compactor rails, moving wet documents out for proper handling, and drying the room. It does not replace document recovery or cleaning.
• Decide together about valuable originals. For very important originals, fragile old records or badly damaged files, consult a document conservation specialist and tell the team in advance so you can decide whether to keep them out of the room.
• Mention electronics. If servers, scanners or copiers are in the room or a connected zone, tell the team so you can plan together.
• Client confidentiality comes first. The ozone team does not need to read any document. Agree the scope of access in advance, have firm staff present during preparation, and keep the room keys with the firm throughout.
• Anyone unwell sees a doctor. Disinfecting the room lowers environmental risk. It is not a cure.

How the job runs in a file room

1. Joint survey with the firm's responsible person: room size, shelving and compactor type, visible mold, remaining damp and how the air conditioning connects, then zoning.
2. Preparation. Firm staff open gaps between compactor units, open cabinets and drawers, lift lids on boxes that are already dry so the gas can reach in, and close windows and vents to the outside.
3. Ozone release. A typical cycle is about 30 minutes per zone, covering fill and contact time.
4. Rest and ventilation. The ozone reverts to oxygen, the room is aired, and only then do people go back in.
5. Handover and advice on humidity control, keeping boxes off the floor and which areas to watch in the following weeks.

Many firms schedule treatment at weekends or after hours so client service is not disrupted.

10 reasons accounting and law firms should consider ozone for their file room after a flood

1. No liquid on documents: ozone is a gas, so paper is not re-wetted.
2. It reaches between shelves and compactor units, where cloths cannot go and air does not move.
3. No chemical residue, because ozone reverts to oxygen. See the service details.
4. It reduces airborne mold spores the team breathes every time they pull a file.
5. It breaks down musty odour at the source, so the storeroom smell stops drifting into client reception.
6. It is quick: about 30 minutes per zone, and can be done out of hours.
7. It is backed by testing from Thailand's Department of Medical Sciences and Intertek (UK), according to the company's certified results. Read about ozone disinfection.
8. It helps protect files that survived from catching mold from a room that flooded.
9. It becomes part of your damage-handling record, which you can explain transparently to clients.
10. It is good value for a whole floor. Jobs of 15,000 baht or more receive a free medical-grade disinfectant spray for desks, cabinet handles and high-touch points. Ask about the promotion.

Before and after: a file room you can trust again

Note: results depend on damage, remaining moisture and cleaning beforehand. Ozone does not repair paper, ink or documents that are already damaged.

Example case: a small law office near Khlong Chan

An illustrative example of how the work fits together, not a real customer review.

Ek is a lawyer who runs a practice with two partners from a shophouse near Khlong Chan. The ground floor holds client reception and a case-file room with four rows of mobile compactor shelving, filled with case files, copies of pleadings and statements, contracts, powers of attorney and supporting documents clients have left with the firm. The water that came in was shallow but stayed for days. The compactor rails were submerged and files in the lowest compartments got wet from below. Higher files stayed dry, but after days in a sealed room the space smelled musty and mold appeared along binder spines.

He worked in order. First, he photographed and listed every affected file. Second, he separated the wet files without squeezing them or forcing stuck pages apart. For critical originals he consulted a document conservation specialist; general documents that were still legible were air-dried in the shade with airflow and scanned as soon as they were dry enough. Third, he told affected clients honestly and requested fresh copies where possible. Fourth, he washed the compactor rails, floor and walls, scrubbed mold following safety advice and ran dehumidifiers until the room was dry. Fifth, he had the air conditioning cleaned and filters replaced.

Then he booked the ozone team for a Saturday when the office was closed. Firm staff stayed through preparation, opened gaps between compactor units, lifted lids on dry boxes and moved originals still with the specialist to another location. Nobody was inside during treatment, and they returned after the rest and ventilation period, then placed new boxes on raised shelves. The following Monday, clients in reception no longer noticed a musty smell from the back, and the team pulled files without discomfort. Ozone was one step in a complete plan, from recording damage and recovering documents to looking after the room.

File-room recovery checklist after the 2026 Bangkok floods

While recovering documents and cleaning

• Have an electrician check wiring before use, especially floor-level sockets and equipment.
• Wear gloves, a mask and eye protection whenever handling flood-wet or moldy documents.
• Photograph, list and date the damage for every box.
• Separate documents into flood-wet, moldy and fine. Do not mix them.
• Do not squeeze, rub or force apart stuck documents. Consult a conservation specialist for critical originals.
• Scan legible documents quickly as a backup.
• Inform affected clients, and get professional advice on legal retention duties.
• Discard wet or moldy cardboard boxes and replace them with new boxes or plastic containers.
• Wash floors, walls, steel shelves and compactor rails. Never mix different chemicals.
• Ventilate, run dehumidifiers and clean the air conditioning.

On ozone day

• Firm staff are present during preparation and hold the room keys.
• Open gaps between compactor units and open cabinets, drawers and the lids of dry boxes.
• Move fragile originals or files still being recovered elsewhere, as agreed.
• Tell the team about servers and electronics in the area.
• No people, pets or plants inside. Re-enter only after the rest and ventilation period.

Back in use

• Keep boxes on raised shelves, away from walls.
• Control humidity consistently and avoid sealing the room for days at a time.
• Recheck boxes stored near former mold spots after two to three weeks.
• Consider moving critical records upstairs and keeping digital backups.
• If staff develop fever, calf pain, diarrhoea or worsening asthma, see a doctor promptly.

FAQ: ozone disinfection for document storage rooms after a flood

1. Can ozone rescue flood-wet documents?

No. Ozone does not dry paper, restore faded ink or separate stuck pages. Wet documents need proper recovery, and critical originals should go to a conservation specialist. Ozone comes afterwards to deal with mold and musty air in the room.

2. Will the team see or open client files?

The ozone team does not need to read anything. Firm staff open cabinets and box lids, access is agreed in advance, and the firm keeps the room keys throughout.

3. Does the office have to close during treatment?

The file room and any zones connected by air must be empty of people, pets and plants, so most firms book weekends or after hours and return after the rest and ventilation period.

4. How long does it take?

A typical cycle is about 30 minutes per zone. Larger or multiple file rooms take longer, plus rest and ventilation. The team confirms the schedule after the survey.

5. Should valuable originals stay in the room during treatment?

Discuss it with the team and a document conservation specialist first. Very fragile originals or files still being recovered may be kept elsewhere so the decision is made carefully.

6. Is one treatment enough?

For flood recovery, most firms treat once after cleaning and drying, and consider another only if damp or mold returns, which usually signals a moisture source still to fix.

7. Is there a promotion?

Ozone jobs of 15,000 baht or more receive a free medical-grade disinfectant spray. Call or message on LINE for current terms.

Protect your clients' records and the air your team breathes

Recover documents, dry the room, then finish with WHD ozone disinfection for your file room.

Book a file-room survey and ozone treatment

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

Related services

• Residential and building ozone disinfection
• Ozone removal of odours and chemical residue, for paint and new-carpet smells after office repairs
• Chemgene HLD4H medical-grade disinfectant, for steel shelving, cabinet handles and desks

References

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