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

More than two hundred messages in the residents' LINE group in a single night

Prae manages the juristic person office of a twenty-something-storey condominium off Lat Phrao. The building has one basement car park level, and on the ground floor sit the lobby, the parcel room, a gym, a children's playroom and the central bin room. On one of the nights of continuous heavy rain in late September 2026, water from the street poured down the ramp into the basement faster than the pumps could clear it. The building technician had to cut power to parts of the basement for safety. One lift was taken out of service after water entered its pit, and the parcel room, where boxes had been stacked on the floor, was soaked almost wall to wall.

That night, the residents' LINE group logged more than two hundred messages. Some asked about their cars, others about their parcels, others shared photos of water in the lobby. A few days later, once the water had dropped and the housekeeping team had shovelled out the mud, a new wave of messages arrived. The lift smelled musty. The parcel room reeked of wet cardboard. The gym, whose rubber flooring had been under water, had a strange smell. And one mother of a toddler asked the question everyone was thinking: is the playroom safe enough for my child to go back in?

Prae knew that answering messages one by one would not be enough. She needed a clear plan, with a sequence, a timetable and a budget she could explain to the committee. Above all, it had to be safe for the hundreds of residents who were still living in the building every day. This guide is written for condominium managers and juristic person committees in exactly Prae's position.

The late-September 2026 Bangkok floods and condominium buildings

According to news reports, between 24 and 27 September 2026 Bangkok received roughly 300 mm of continuous heavy rain in about 48 hours, and 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 Sittipunt said the canals were full and drainage would take around two to three days after the rain stopped.

Reports noted three deaths, one of them an electrocution in a car park, a sober reminder for every building with an underground car park that electrical safety comes before any recovery work. As of 30 September, some roads such as 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 business report cited a Chamber of Commerce estimate of around 12,300 million baht in damage.

For condominiums, the damage is rarely inside the units on upper floors. It sits in the basement and on the ground floor, in the common areas everyone shares. Responsibility for recovery therefore falls squarely on the juristic person.

Why condo common areas collect germs and mold after a flood

Common areas differ from private units because many people use them all day, and many of them are enclosed rooms with poor ventilation. When floodwater gets in, problems stack up in layers.

Lifts and lift lobbies

A lift car is a small sealed box that residents enter hundreds of times a day. After a flood, wet shoes, umbrellas and belongings carried up from the ground floor bring damp and dirt inside. If the lift pit held water, moisture can rise up the shaft. Buttons, handrails and lift walls are shared touch surfaces that need special attention.

Parcel rooms and storerooms

Cardboard that has soaked in floodwater is an excellent breeding ground for mold. Wooden shelving, walls that wicked up water and humidity trapped in a closed room turn the parcel room into the mustiest space in many buildings, and it is one residents visit every day.

Central bin rooms and refuse chutes

A flooded bin room holds dirty water mixed with food waste, which attracts cockroaches and rats, and floodwater brings drain-borne germs with it. Public health bodies including the WHO, the US CDC and Thailand's Department of Disease Control warn of gastrointestinal illness, skin problems and leptospirosis from contact with floodwater and sewage.

Gyms, playrooms and multipurpose rooms

Rubber flooring, foam mats, equipment padding, toys and carpets all hold water and are hard to dry completely. These rooms are usually air-conditioned with doors closed, ideal conditions for mold. Their users are small children and people breathing deeply during exercise.

Lobbies, corridors and fire stairs

Fabric sofas, corridor carpets and gypsum walls that drew water up from the floor are all sources of mustiness. Fire stairs are closed spaces with almost no ventilation, so damp that gets in tends to stay.

Plant rooms and staff rooms

Housekeeping rest rooms, security rooms and technicians' rooms on the ground floor are where staff spend hours each day, yet they are often left out of recovery plans, even though staff are the people who waded through water and cleared the mud.

Health agencies consistently advise cleaning and drying within 24 to 48 hours to limit mold growth. In a large building surrounded by standing water for days, achieving that everywhere at once is rarely possible.

Who in the building is most affected

Older residents who must use the lift every time they leave their unit and often have underlying conditions. Damp, musty air in lifts and lobbies can irritate their airways.

Young children who play on the playroom floor, put toys in their mouths and are more vulnerable to germs than adults.

Pregnant women and people with chronic illness, who should avoid exposure to mold spores and flood-borne germs.

People with allergies and asthma, who may react simply from walking past the parcel room or waiting in the lobby.

Housekeepers, security guards and technicians, who work in the riskiest areas every day. Anyone who waded through water and then develops a fever, muscle pain (especially in the calves), red eyes or diarrhoea must see a doctor and mention their floodwater exposure.

The impact on the juristic person and co-owners

• Health: common areas are where every resident passes. If mold or germs build up there, the effect spreads through the entire building.
• Cost: mold that spreads through gypsum walls, ceilings or carpets may later force removal and replacement, costing far more than early treatment, and the money comes from the common fund.
• Time and management: complaints arriving one at a time consume enormous staff hours. A clear plan cuts down on repeated questions.
• Property value: buyers and tenants viewing a unit always walk through the lobby and lift first. Mustiness in common areas damages the image of the whole project.
• Trust: residents judge the juristic person by how it handles a crisis. Transparent communication and systematic action build goodwill ahead of the next general meeting.

Common approaches in condos, and why they fall short

Mopping with ordinary floor cleaner and calling it done: visible floors look cleaner, but walls that absorbed water, the space beneath shelving, behind cabinets and the air in closed rooms remain untouched.

Strong bleach throughout the building: chlorine smell in the lobby and lifts irritates residents, may damage finishes, and is dangerous if staff mix it with other products.

Scent diffusers and air freshener sprays: they mask odour for a few hours but do not reduce mold, and many residents react badly to synthetic fragrance.

Painting over mold stains: the wall looks new, but mold beneath the paint survives and often reappears as blotches within months.

Treating only rooms that draw complaints: chasing problems room by room means damp spaces nobody has complained about yet, such as fire stairs or staff rooms, are forgotten and become next month's problem.

WHD ozone disinfection for condominium common areas

World Health Disinfection (WHD) provides a residential and building ozone disinfection service for homes, condos, hotels, offices, factories, schools and hospitals. According to the service information, ozone (O3) breaks down the cell structures of viruses, bacteria and mold, as well as odour molecules, then reverts to oxygen (O2) with no chemical residue. According to test results certified for the company, with testing by Thailand's Department of Medical Sciences and Intertek (UK), ozone treatment eliminates viruses, bacteria and mold by 99.99%. A typical cycle takes about 30 minutes per zone.

For a condominium, the key is to divide the common areas into zones that can be closed off and treat them one at a time while the rest of the building carries on as normal. Open spaces that cannot be sealed, such as car park decks with openings on every side, are not suitable for ozone treatment. The team will help assess which spaces can genuinely be closed and treated effectively.

A six-phase whole-building common area ozone plan

1. Phase 1, survey and zone map: walk the building with the technician, identify rooms that flooded, rooms that smell and rooms that can be closed. Set priorities, for example playroom, parcel room, lifts, bin room, gym and staff rooms.
2. Phase 2, safety and cleaning: an electrician confirms the electrical system in each area is safe. Then remove mud, discard damaged boxes and materials, wash and wipe surfaces, and run fans or dehumidifiers until the area is dry. Ozone comes after cleaning and drying; it never replaces them.
3. Phase 3, timetable and resident notices: decide which zone closes on which day and time, choose low-use periods, and notify residents in advance via the LINE group, notice boards and signs on each door.
4. Phase 4, treat zone by zone: close off the zone, confirm nobody and no pets are inside, post no-entry signs, station a staff member at the entrance, and only then begin.
5. Phase 5, rest period and reopening: wait for the rest and ventilation period recommended by the team before reopening to residents.
6. Phase 6, report and aftercare plan: summarise each zone, date, time and before/after condition for the committee, and set monthly moisture check points.

Safety rule to remember: ozone treatment must only take place in an empty, closed space with no people, pets or plants inside. In a condominium that means sealing the zone, posting signs and keeping someone at the entrance throughout. Residents and staff may re-enter only after the rest and ventilation period. Ozone is not medical treatment; anyone who feels unwell must see a doctor.

Whole-building common area jobs often exceed 15,000 baht, which qualifies for WHD's free medical-grade disinfectant spray promotion. Housekeeping can use it afterwards on shared touch points such as lift buttons and door handles.

A sample resident notice you can adapt

Clear notices prevent most of the confusion around common area treatment. A short notice posted three days ahead in the LINE group, on the notice board and on the door of each zone might read:

"Dear residents, following the late-September floods, the juristic person office will carry out ozone disinfection of common areas after cleaning and drying are complete. On [date], from [time] to [time], the parcel room, storerooms and bin room will be closed. Parcels can be collected at the temporary desk in the lobby. Please do not enter any area with a no-entry sign until staff reopen it. Ozone treatment takes place only in empty, closed spaces. If you have questions, please contact the office."

Add one line per zone and day, name a contact person, and repeat the message the evening before. When a zone reopens, post a short follow-up so residents know they can use it again. Do not forget upper-floor spaces either: rooftop function rooms, sky lounges and upper-floor gyms may not have flooded, but residents carried wet umbrellas and shoes through them for days, so the survey should check them for damp as well.

10 reasons a juristic person should plan whole-building common area ozone treatment

1. Fix the system, not one complaint at a time. A plan covering every zone means nothing is forgotten.
2. The gas reaches what mops cannot. Behind parcel shelves, under gym equipment and through the air in closed rooms.
3. No lingering smell or chemical residue in shared spaces. Suitable for buildings with young children, older residents and sensitive people.
4. Backed by testing. According to test results certified for the company by the Department of Medical Sciences and Intertek (UK); see the ozone disinfection service page.
5. Zone by zone while the building stays open. About 30 minutes per zone allows scheduling in low-use hours.
6. Easy to explain to the committee. A plan, zones, a timetable and a summary report keep budget approval transparent.
7. Clear communication with residents. Advance notices with time slots reduce confusion and complaints.
8. Staff are cared for too. Housekeeping and security rooms sit in the same plan as residents' spaces.
9. Less chance of tearing out materials later. Dealing with mold early protects the common fund's repair budget; read more about the building ozone service.
10. Protect the project's value. A fresh lobby and lift are the first impression for buyers and tenants.

Before and after ozone treatment of common areas

Example case: a three-day timetable for a 400-unit condo off Lat Phrao

(An illustrative planning example, not a review from any specific customer.)

Imagine Prae applying the six-phase plan to her building. After the electrician confirmed the ground floor was safe and housekeeping finished cleaning, she ran dehumidifiers in the parcel room and gym for two days, then scheduled three days of treatment.

Day one, late morning on a weekday: the parcel room, storerooms and central bin room, with a temporary parcel desk set up in the lobby. Day two: the playroom, gym and multipurpose room, announced as closed from morning to afternoon. Day three, late at night when lift traffic is low: the lift cars one at a time, with the other lifts running normally, plus the ground-floor lift lobby, staff rest room and security room.

Every zone had no-entry signs and a staff member at the door. Residents received notice three days ahead with the full timetable. At the end, Prae had a one-page report listing every zone, date, time and step, ready for the committee. The most visible change was in the LINE group: complaints gave way to a single question, "When does the playroom reopen?"

Juristic person checklist before and after ozone treatment

Before ozone treatment

• Have an electrician inspect basement and ground-floor power before anyone works there.
• Have the lift contractor inspect pits and systems before returning lifts to service.
• Staff wear gloves, boots and masks while clearing mud.
• Discard boxes, carpets and materials ruined by water, and photograph them as a record.
• Wash and wipe surfaces, and disinfect shared touch points with a product such as Chemgene HLD4H at the label dilution.
• Run fans or dehumidifiers until spaces are dry.
• Draw up the zone map, set the timetable and notify residents in advance.
• Move ornamental plants out of the lobby and any zone to be treated.
• Prepare no-entry signs, barrier tape and staff to guard entrances.

After ozone treatment

• Reopen spaces only after the rest and ventilation period advised by the team.
• Check again for smells and damp, especially in corners and behind shelving.
• Keep wiping shared touch points daily.
• Set monthly moisture checks in the parcel room, fire stairs and staff rooms.
• Present a report with photos to the committee and tell residents which areas have reopened.
• If any area smells of paint or adhesive from repairs, consider the ozone chemical-residue and odour removal service.
• Staff with fever, calf pain or diarrhoea after wading should see a doctor.

Frequently asked questions from juristic persons about common area ozone treatment

Do we have to close the whole building?

No. A good plan divides the building into zones that can be closed and treats them one at a time, while residents continue living in their units and use other routes in and out. The zone being treated, however, must have nobody inside.

How can lifts be treated when residents need them all the time?

One at a time, during low-use hours. The lift contractor locks that car out of service with doors closed while the other lifts run normally, until the rest and ventilation period is over.

Can the basement car park be treated?

It depends on whether the space can truly be sealed. Car park decks open on all sides are not suitable for ozone. The team will assess the site and recommend which basement rooms can be closed and are worth treating; open areas should focus on washing, drying and ventilation.

Do we need a general meeting resolution first?

That depends on your building's regulations and the spending limit the committee can approve. A plan with zones, a timetable and a clear report makes it easier to explain to the committee or the meeting.

Can residents ask for their own units to be treated too?

Yes. Residents can contact WHD directly to treat their unit, and they must leave with pets and plants during treatment just the same. The juristic person may collect names so unit visits can be scheduled alongside the common area work.

Will it need repeating?

If the source of damp has been fixed, such as leaks repaired and spaces fully dry, frequent repeats may not be necessary. Keep up routine moisture checks, and if mustiness returns, always find the cause first.

After ozone, do residents no longer need to worry about flood-related illness?

No. Ozone reduces germs in spaces but does not treat or prevent illness in people. Anyone who had contact with floodwater and feels unwell must see a doctor.

Turn complaints in the LINE group into a plan residents trust

The WHD team is ready to walk your common areas with the juristic person office and design a zone plan and ozone timetable that fits your building.

Book a Whole-Building Ozone Survey

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

Related links

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

References

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