A major Bangkok flood, and the office repair season that follows

According to news reports, Bangkok received roughly 300 mm of continuous heavy rain in about 48 hours between 24 and 27 September 2026, causing widespread flooding. On 26 September 2026 the Bangkok Metropolitan Administration declared all 50 districts a disaster zone. Eastern Bangkok was hit hardest, with 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.

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 2011 floods, and one Thai business report cited a Chamber of Commerce estimate of about 12,300 million baht in damage. For many companies, especially those on the ground floor of shophouses and small office buildings, that damage means closing temporarily, stripping out, rebuilding and reopening as fast as possible. That is where a problem many businesses never anticipated begins.

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

The first Monday back, and a desk covered in sick-leave forms

Nan is the HR and administration manager of a 25-person accounting firm that rents the ground and first floors of a four-storey shophouse off a soi in the Lat Phrao area. On the night of the heaviest rain, water from the street rose to mid-shin on the ground floor. The carpet tiles were submerged, the particleboard bases of the desk partitions swelled and delaminated, the steel filing cabinets started rusting at the edges, and client files in the bottom drawers were soaked and had to be dried and re-scanned.

Management decided everyone would work from home for two weeks while a contractor rebuilt the whole ground floor at once. They pulled up the old carpet, glued down new carpet tiles, repainted every wall, installed new melamine desks and partitions, laid an epoxy floor in the document store, and replaced swollen timber doors. The work finished on Friday night, and everyone came back on Monday morning.

By ten o'clock two accountants complained of a dull headache. By the afternoon others had stinging eyes and blocked noses. A junior colleague with asthma needed her inhaler twice, and a staff member five months pregnant asked to go home because the smell made her nauseous. By Wednesday Nan had three sick-leave forms on her desk and the staff LINE group was full of messages like "the office stinks" and "I feel dizzy after sitting here all day", even though everything looked newer and cleaner than before the flood.

Nan ordered three more air purifiers, propped the front door open in the mornings and asked the housekeeper to spray air freshener every hour. The result was a floral scent mixed with glue, and complaints that did not stop. She began to suspect that the issue was not just "new-office smell" but indoor air quality affecting the health and productivity of the entire team.

What VOCs are, and why a post-flood office renovation is especially risky

VOCs, or volatile organic compounds, are chemicals that evaporate at room temperature. They are found in almost every building and fit-out material: wall paint, thinner, lacquer, carpet adhesive, vinyl tile glue, silicone, epoxy, cleaning products, and engineered wood panels such as particleboard and MDF used for desks and partitions. Familiar examples include formaldehyde, toluene and xylene.

Why offices accumulate more VOCs than people expect

Most Bangkok offices are designed as sealed, air-conditioned rooms. Windows are often fixed or never opened. Split-type air conditioners in shophouse offices recirculate indoor air instead of bringing in fresh outdoor air. When one floor receives a large volume of new materials at the same time (wall-to-wall carpet, twenty-plus desks, partitions and fresh paint), the amount of VOCs released in the first week is high, and there is nowhere for it to go.

Worse, overnight and at weekends, when the air conditioning is off and the office is locked, these compounds build up further. The first person to arrive on Monday morning usually experiences the strongest smell.

The flood factor: mustiness and mold hiding under new finishes

An office that was underwater has another group of odours mixed in: dampness and mold that may grow inside walls, under floors, in ceilings where water wicked upwards, and in paper files that got wet. If a contractor lays new carpet on a slab that is not fully dry, or paints over walls that are still damp inside, the moisture is trapped and becomes a continuing odour source. The CDC advises cleaning and drying within 24 to 48 hours to limit mold; in this flood, many buildings could not manage that because street water had not yet receded.

Symptoms staff commonly report

Breathing higher concentrations of VOCs for hours at a time commonly causes headaches, dizziness, irritation of the eyes, nose and throat, nausea, fatigue, drowsiness and poor concentration, and can trigger asthma or allergy flare-ups in some people. These symptoms often improve after leaving the building and return on re-entry, a pattern often grouped under the term "sick building syndrome".

Staff who need extra care

Pregnant employees, people with asthma, allergies, chronic lung disease or migraines, older staff and anyone sensitive to chemical smells deserve particular consideration, for example extra time working from home or seating near better ventilation. Anyone with severe or persistent symptoms such as difficulty breathing, chest tightness, or fever and calf pain after wading through floodwater (possible signs of leptospirosis) must see a doctor promptly. This article is not medical advice.

The hidden costs of poor office air after a flood

Health: small problems that add up every day

One day of headaches or stinging eyes may seem minor. But when staff sit in the same environment eight to ten hours a day, five days a week, small discomforts accumulate into fatigue, stress and illness that leads to sick leave.

Productivity

People who feel foggy all day think more slowly, make more mistakes and step outside for fresh air more often. In precision work such as accounting, finance or design, small errors can become big costs later. At a time when the company is already racing to clear the backlog from the flood closure, lost productivity hurts twice as much.

Money: sick days, backlog and extra purifiers

Sick days, overtime to catch up, air purifiers and replacement filters bought without effect, and rent paid for space that cannot be fully used all pile on top of flood repair bills that are already heavy.

Trust and reputation

When employees feel the company is not paying attention to workplace safety, trust erodes and some may start looking for new jobs. If clients arrive for a meeting and smell chemicals or damp, the firm's image suffers too. Thailand has occupational safety, health and working environment legislation that requires employers to keep the workplace safe for employees, and managing indoor air quality after a renovation is part of that responsibility.

Employees' families

Staff who go home every evening with a headache and no energy have less to give their families, at a time when many of them are also repairing their own flooded homes.

Why the fixes most offices try don't work

Air freshener sprays and aroma diffusers

Fragrance only masks the problem without reducing the original chemicals, and fragrance compounds are themselves VOCs. Staff already suffering from chemical headaches usually feel worse when strong scents are added.

Buying more air purifiers

Most purifiers on the market rely on HEPA filters designed for PM2.5 dust, not gas molecules like VOCs. Units with a carbon layer help somewhat, but against a whole floor emitting from every surface, a few machines simply do not have the capacity.

Leaving the door open in the morning

An open door only helps the area near the door. In the rainy season the outdoor air is very humid; once the air conditioning runs, moisture condenses and can worsen mustiness. A street-level office also pulls in dust and traffic fumes instead.

Waiting for the smell to go away

VOC levels do fall over time, but the peak is right after installation, which is exactly when staff return. Doing nothing means employees take in the worst of it, and some materials such as engineered wood keep emitting for a long time.

Mopping with strong-smelling cleaners

Scrubbing with heavily scented cleaners or large amounts of bleach in a sealed room can add to the chemical load, and it does nothing about VOCs coming from inside the materials themselves.

Ozone chemical odour removal for offices by World Health Disinfection

World Health Disinfection (WHD) provides an ozone chemical-residue and odour removal service for homes, condos, offices, factories, construction sites, hotels, storage facilities and vehicles. According to the service information, ozone breaks down odour molecules at the source rather than masking them, covering paint, thinner, epoxy and lacquer odours, VOCs and musty smells, and also helps deal with bacteria, viruses and mold. Ozone then reverts to oxygen and leaves no residue.

Why ozone suits a renovated office

An office has a huge number of surfaces emitting at once: carpet across the whole floor, the underside of desks, inside drawers, behind partitions, and the epoxy-floored document store. Wiping or spraying every one of them is practically impossible. Ozone, as a gas, spreads through a sealed space, reaches places hands cannot, and works within a limited time window such as Friday evening or the weekend, when nobody is at work.

What HR teams and managers value most is that, according to the service information, WHD measures TVOC with calibrated instruments before and after treatment. The readings let the company communicate transparently with staff instead of just saying "it's been dealt with", and they serve as a record of the organisation's workplace-safety efforts.

How the office service works

1. Assessment and planning. The team asks about floor area, number of rooms, new materials installed, the air-conditioning system and when the office will be empty.
2. Baseline TVOC measurement at key points such as workstations, meeting rooms and the document store.
3. Preparing the space. All staff, cleaners, any office pets and plants leave the area. Doors and windows are closed to create a sealed space; drawers, storage cabinets and internal doors are opened.
4. Ozone treatment with a Master Ozone Generator, positioned according to the floor plan, with concentration and duration set appropriately.
5. Rest and ventilation. The ozone reverts to oxygen. "No entry" signs go up and building security or management is informed.
6. Post-treatment TVOC measurement, compared with the baseline, with a summary sent to management.
7. Back to work. According to the service information, the space is ready to use about 2 hours after treatment, so a weekend treatment fits a normal Monday opening.

Safety note: ozone treatment is carried out only in an empty, closed space. No people, pets or plants may be present until the rest and ventilation period has ended, because ozone at treatment concentrations irritates the airways. Ozone comes after mud removal, washing and drying. It does not replace removing soaked materials, cleaning, or medical care. Staff who feel unwell should see a doctor.

10 reasons to ozone-treat your office after a post-flood renovation

1. It reduces the source of the odour causing headaches, rather than covering it with fragrance. Details on the ozone chemical odour removal page.
2. It covers large areas in one session: workstations, meeting rooms, document stores and corridors.
3. It reaches under desks, inside drawers and behind partitions, where engineered wood emits the most.
4. It helps reduce mustiness in areas that were flooded, including archives where paper got wet.
5. It helps deal with bacteria, viruses and mold, according to the service information, as an extra layer after cleaning.
6. No residue on desks, keyboards or documents, because ozone reverts to oxygen.
7. Before-and-after TVOC numbers to share with staff, building transparency and confidence. See the process on WHD's service page.
8. It can be done outside working hours, and the space is ready about 2 hours later, so operations are not disrupted.
9. It helps cut sick days and restore productivity while the company clears its backlog.
10. It shows you care about employee safety, with a professional team and a Master Ozone Generator. Contact WHD.

Before and after ozone: how the office feels

Note: results depend on floor area, materials, the air-conditioning system and any remaining moisture. Any damp spots must be fixed first.

Example case: a ground-floor design studio in eastern Bangkok

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

Boy is a partner in a 12-person interior design studio occupying the ground floor of a shophouse in eastern Bangkok. After the water receded, his own team designed the repair: removing laminate flooring and replacing it with glue-down vinyl tiles, repainting the walls, building a lacquered plywood shelf for material samples and buying a new meeting table.

Boy knew these materials would smell, so he planned for every smell-producing job to finish by Thursday. Friday was for running fans and checking the walls for moisture. He booked the WHD team for Saturday morning. The team measured TVOC at three points, asked for the ornamental plants and fish tank to be moved out, opened every drawer and cabinet, set up the ozone generator, sealed the area, informed building security, and waited for the rest and ventilation period to finish before measuring TVOC again.

On Monday morning Boy posted the before-and-after summary to the team chat, invited anyone who felt unwell to say so immediately, and told colleagues who were pregnant or asthmatic they could keep working from home for a while if they felt uncomfortable. What he said was most worthwhile was not only the reduced smell but that the team felt the company "thought of them first" after a week of repairing their own homes.

Checklist for HR and facility managers before reopening after a flood

Before renovation

• Have an electrician inspect wiring, breakers and sockets that were submerged before switching on.
• Remove mud and soaked materials such as carpet, ceiling boards and lower gypsum, with workers in gloves, boots and masks.
• Wash surfaces, then disinfect with a suitable product such as Chemgene HLD4H, following the label dilution and contact time.
• Dry floors and walls fully with fans and dehumidifiers before new flooring or paint.
• Separate wet files to dry or scan, and dispose of moldy paper appropriately.

During renovation

• Choose low-VOC paints and adhesives, and furniture with low formaldehyde emission ratings where possible.
• Schedule strong-smelling work to finish several days before reopening.
• Clean air-conditioner filters and have the system checked.

Before and after ozone

• Book treatment for a day with no staff; inform building management and security; post "no entry" signs.
• Move plants, aquariums, pets, food and drinks out.
• Open drawers, cabinets and internal doors so the gas spreads evenly.
• Tell the team in advance about any high-value equipment or important documents to move.
• Afterwards, ventilate as advised and keep the TVOC readings on file.

Day one back

• Tell staff clearly what was done and share the measurements.
• Provide a way to report symptoms and allow at-risk staff to work from home if needed.
• Remind anyone who waded through floodwater to watch for fever, muscle pain or diarrhoea and to see a doctor if they occur.

Frequently asked questions

If staff get headaches in the new office, is it definitely VOCs?

Not necessarily; headaches have many causes. But if several people develop symptoms at the same time after a renovation and feel better when they leave the building, indoor air quality should be checked. TVOC measurement gives a clearer picture, and anyone with persistent symptoms should see a doctor.

How long does the office need to close?

Nobody may be in the area during treatment, rest and ventilation. According to the service information, the space is ready about 2 hours after treatment, so most organisations choose a weekend or after-hours slot.

Do computers, printers and documents need to be moved out?

The team assesses the site and advises. If you have high-value equipment, important documents or materials you are concerned about, mention them in advance so they can be moved or handled appropriately.

Do we still need ventilation after ozone?

Yes. Ventilation is always part of the procedure, and in the long run the office should bring in fresh air regularly, because some materials continue to emit for a while.

Does ozone also help with post-flood germs?

According to the service information, ozone helps deal with bacteria, viruses and mold, but only after mud removal, washing and surface disinfection. It is not a shortcut that replaces cleaning.

Our office is in a shared building. Who should we coordinate with?

Inform the building's management, security and neighbours on the same floor to agree the timing and area and to make sure nobody enters during treatment.

Should we treat again if more furniture arrives?

If a large amount of new material or fresh paint is added after treatment, measure TVOC again before deciding.

Make your rebuilt office a place where your team can breathe easily

Talk to WHD about ozone treatment for chemical odours and VOCs in your office, with TVOC measured before and after. After-hours scheduling available.

Book Office Ozone Treatment

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 and cleanup
• WHO fact sheets