A Story from the Field: Auntie Somsri and Her Eight Rooms Behind the Market

Auntie Somsri is sixty-one. She owns a single-storey row of eight rental rooms down a small lane behind a market in the Mahachai area of Mueang Samut Sakhon. For more than ten years she has rented them out at budget prices. Almost all of her tenants work in seafood processing plants or in the market itself. Some rooms are shared by two or three people. Many work the night shift, others the morning shift, so the rooms are almost never empty at the same time.

During the October 2026 floods, water from the road in front of the market poured into the lane and flooded the whole row almost to knee height. It stayed for several days. Some tenants lifted their mattresses onto chairs. Others went to sleep at friends' dormitories. As soon as the water went down, everyone had to come straight back: they had shifts to work and nowhere else to live.

What Auntie Somsri found was a stale, musty smell mixed with the fishy odor of market water. The tiled floors were coated in a thin film of mud. The lower parts of the plastered walls carried water marks, and black spots were starting to appear. The shared bathroom at the back smelled of sewage backing up from the drains. One tenant developed an itchy rash on his legs. Another started coughing at night. Auntie Somsri was worried about her tenants' health and about her property. But she was equally worried that if everyone had to move out at once for disinfection, they would have nowhere to go, and might never come back.

This article is written for owners of row houses and budget rental rooms in Mahachai, Tha Chalom, Khok Kham and nearby areas who need to recover after the flood while their tenants keep living and working as normal. It explains the risks specific to this kind of property, why common clean-up methods fall short, and how a room-by-room plan of disinfection fogging and ozone treatment can work around shift schedules.

Why Rental Row Houses Near a Market Face Extra Risk

• The water passed through the market first. It carried food scraps, fish waste, wastewater from stalls and germs from the drains into the rooms. The smell is stronger and lasts longer than ordinary flood odor.
• Rooms are densely occupied. A single room may house several people. Belongings, clothes and bedding are pushed against the walls, so moisture has nowhere to escape.
• Mattresses sit directly on the floor. Many tenants sleep on thin mattresses or mats laid on the tiles. While the floor is still damp, mold grows underneath where no one sees it.
• Bathrooms and washing areas are shared. If these spaces are not properly disinfected, germs pass easily from one room to the next.
• Few windows. Many older row houses only have vents at the front, with the back wall shared with the bathroom block. Air goes stale quickly.
• Tenants work shifts. Rooms stay closed during the day while night-shift workers sleep, so humidity and odor build up.

Each of these factors on its own is manageable. Together, they turn a row of small rooms into a place where the musty smell keeps returning and mold spreads from one unit to the next unless the whole row is treated in a coordinated way.

Impacts Landlords Should Not Overlook

Tenant health. Floodwater that has passed through a market and the drainage system may carry organisms that cause diarrhea, skin infections, and those associated with leptospirosis. Mold on walls and under mattresses can trigger allergies and coughing. If a tenant develops a fever, muscle pain or an inflamed wound after wading through floodwater, encourage them to see a doctor. This article is not medical advice.

Rental income. Budget rooms earn a modest margin per room. If tenants leave because they cannot stand the smell, or because they keep getting sick, even one month of vacancy can dent the whole year's income.

Reputation among tenants. Workers in the same neighborhood talk to each other about which rooms are good and which landlords do not take care of their property. Word of mouth matters far more than any sign on the gate when it comes to finding new tenants.

The building itself. Old plaster walls that have soaked up water, wooden door frames and wooden doors will rot and need replacing sooner if mold is allowed to spread. Repairs later will cost more than acting now.

Why the Usual Clean-Up Is Not Enough

• Hosing down the floor. It removes mud but leaves behind germs that have soaked into grout, plaster and door frames.
• Pouring strong bleach. In a small, poorly ventilated room, the fumes make breathing uncomfortable, especially for tenants who must sleep there that night.
• Burning mosquito coils or incense to mask the smell. It covers the odor temporarily and adds smoke to a room that already lacks airflow.
• Painting over black marks. If the wall is still damp, the paint will bubble and the mold will return within weeks.
• Everyone doing their own thing. When each tenant cleans their own room as they see fit, some rooms end up clean and others are never touched. Germs and odor from one room then affect the rooms next door.

The common thread is that none of these methods reaches deep into porous surfaces or treats the air, and none of them is coordinated across the row. A planned approach solves both problems.

The Solution: Rotating Disinfection Fogging and Ozone Treatment, One Room at a Time

The World Health Disinfection (WHD) team plans a disinfection fogging service using CHEMGENE HLD4H through ULV fogging equipment. The ultra-fine mist reaches wall crevices, the space under beds, behind cabinets and the corners of bathrooms. Then comes ozone treatment, which helps reduce mold spores and the musty odor trapped in walls and fabrics. What makes a row-house rental job different is the scheduling: the order of rooms is planned around the tenants' shifts.

How the Work Is Done

1. Survey the whole row with the owner. We look at the water line, walls, door frames, the shared bathroom and the drainage channel behind the rooms, and we ask about the shift schedule of each room.
2. Advice on clearing belongings and mud. Mattresses, thin floor mattresses and mats that sat in floodwater should be thrown away. Clothes that are still usable should be washed in hot water and dried in the sun. Mud should be washed off floors and out of drainage channels before fogging day.
3. Start with shared areas. We fog the shared bathroom, the washing area and the back walkway first, because everyone uses them.
4. Go room by room according to shifts. Rooms of night-shift workers are treated in the early evening before they leave for work. Rooms of morning-shift workers are treated late in the morning. Nobody is left without a place to rest for the whole day.
5. Controlled ozone treatment. Each empty room is sealed and treated for a duration suited to its size. During treatment there must be no people, pets or plants inside. Sensitive electronics should be removed or covered.
6. Ventilate and hand the room back. Doors and windows are opened for the time the team specifies, until there is no ozone smell, and only then do tenants go back in.
7. Re-check and aftercare advice. We check the odor and risk points again and advise the owner on long-term humidity control.

Ozone safety: No people, pets or plants may be inside a room during ozone treatment, and the room must be fully ventilated before anyone goes back in. For neighboring rooms where people are resting, the team seals vents and gaps between rooms and controls the dose so that the gas does not leak across.

Tips for Communicating with Tenants So Everyone Cooperates

Give notice in a language tenants understand. Some tenants may not read Thai fluently. A short notice with pictures, showing the date, time and what to prepare, works well. You can also ask a tenant who speaks several languages to help translate.

Be clear about how many hours they need to be out. Shift workers can plan much more easily when they know the exact window, ideally one that falls while they are already at work.

Offer a temporary waiting spot. If you have an empty room or a covered space in front of the row, set up somewhere for tenants with nowhere to go during the ventilation period.

Ask for help with belongings. Ask tenants to pack food, valuables and important documents into closed bags or boxes, to put soaked mattresses out for disposal, and to pull belongings away from the walls so the mist can reach.

Explain that it is for everyone's health. When tenants understand that the landlord genuinely cares, cooperation improves dramatically, and they are more likely to stay.

Landlord Checklist Before the Team Arrives

• Photograph the water marks, walls, floors, shared bathroom and damaged items in each room. These records help with any relief applications or insurance claims.
• Make a list of rooms, the number of tenants in each, and their shift times, so the team can plan the order right away.
• Arrange for soaked mattresses and furniture to be removed before fogging day, and check with the municipality about bulky waste collection points.
• Clear mud out of the drainage channels at the back and front, and open drain covers so water flows freely.
• Have an electrician check ground-level sockets and wiring that were under water before power is used, for the safety of tenants and the team.
• Prepare a waiting area for tenants who need to leave their room during ozone treatment, such as an empty room or a covered front yard.

With this preparation done, work on the whole row can proceed without stopping between rooms, and tenants lose as little time as possible. That matters a great deal for workers who need proper rest before their next shift.

Ongoing Care After the Flood So Odor and Mold Stay Away

Row houses near a market can turn damp again quickly without ongoing care. Agree with tenants on a weekly cleaning roster for the shared bathroom and washing area. Use a disinfectant spray to wipe door handles, taps and light switches. Ask tenants to place their mattresses on a low platform or raised base instead of directly on the tiles, and to open doors and windows during the day whenever no one is sleeping.

For the first one to two months after the water recedes, walk the whole row once a week. Look at the lower walls, door frames and the space under cabinets. If you see new black spots or the musty smell returns, contact the team early for a re-assessment, before the problem spreads to several rooms.

It also helps to remove standing water around the row. Buckets, old tires and blocked gutters that hold rainwater become mosquito breeding sites within days. Clearing them, and arranging mosquito control where needed, protects tenants who already spend long hours in crowded workplaces.

An Example Schedule for an Eight-Room Row

Every row is different, but an example helps landlords picture how the work fits around real lives. Imagine a row like Auntie Somsri's, with four rooms of night-shift workers and four rooms of morning-shift workers.

• Before the day: soaked mattresses are out, mud is washed away, the electrician has checked the sockets, and each tenant knows their time slot from a picture notice on the gate.
• Late morning: the team fogs the shared bathroom, the washing area and the back walkway. Morning-shift tenants are already at work, so their four rooms are fogged and then ozone-treated in pairs, with vents to occupied rooms sealed.
• Early afternoon: the first rooms are ventilated while the next pair is treated. Night-shift tenants are resting in their own rooms, which are untouched for now, or in the waiting area if they prefer.
• Early evening: morning-shift tenants come home to rooms that have been aired out. Night-shift tenants leave for work, and the team fogs and ozone-treats their rooms in turn.
• Before the night ends: the last rooms are fully ventilated, so night-shift workers come home to fresh rooms at the end of their shift.

The exact timing depends on room size, the level of contamination and the weather, and the team confirms it after the survey. The principle is simple: no tenant is without a place to rest at a time when they need to sleep.

Common Mistakes Landlords Make After a Flood

• Waiting for tenants to complain. By the time someone complains, mold is often already established behind furniture and under mattresses. Walking the row yourself in the first week saves money later.
• Treating only the worst room. Odor and germs move through shared walls, gaps under doors and connected drains. A partial job often means paying twice.
• Repainting before the walls are dry. Fresh paint on damp plaster looks good for a few weeks, then bubbles and turns black again.
• Keeping soaked mattresses "because they look fine." A dry-looking surface does not mean the core is clean. Replacing mattresses is far cheaper than losing a tenant to repeated illness.
• Forgetting the drains. A blocked drain or inspection chamber keeps pushing sewage odor back into the bathroom no matter how often it is cleaned.

10 Reasons Row-House Landlords Choose Our Service

1. The whole row is disinfected to one standard, not room by room at random.
2. Rooms are scheduled around shifts, so tenants do not have to move out at the same time.
3. Work starts with the shared bathroom and washing area, the highest-risk spots.
4. It uses CHEMGENE HLD4H, suitable for surface disinfection in residential settings.
5. Ozone treatment reduces fishy and musty odors that washing cannot remove.
6. It helps reduce mold spores in rooms where many people sleep.
7. Clear ozone safety procedures that also protect neighboring rooms.
8. It helps you keep existing tenants and reduces the risk of vacancies.
9. Long-term care advice, including our mosquito spraying service for standing water behind the rooms.
10. Landlords can continue the care themselves with the CHEMGENE 750 ml spray for shared bathrooms and door handles.

Before and After: A Rental Row After the Water Recedes

What the Landlord Said

"What I feared most was that my tenants would move away. The team looked at everything, did the shared bathroom first, then went room by room while the young ones were at work. Nobody had to sleep outside. The fishy smell in the walls is much weaker now, and the tenants say they sleep better. Every room is still occupied."

Auntie Somsri, row-house landlord in Mahachai (story from the field)

Frequently Asked Questions

1. Do all the tenants have to move out?
No. The team schedules rooms one at a time around shifts. Tenants only need to leave during ozone treatment and the ventilation period that follows.

2. Will neighboring rooms with people sleeping be affected?
The team seals vents and gaps between rooms and controls the dose and duration so the gas does not leak next door. Where two rooms are very open to each other, we may treat them together in one round.

3. Can a mattress that sat in floodwater be used again after ozone treatment?
We do not recommend it. Mattresses soaked in floodwater hold contaminated water deep inside. Ozone helps with odor, but it does not dry or clean the core. They should be thrown away and replaced.

4. The shared bathroom smells of sewage. What should I do?
Have a plumber check the pipes and inspection chambers for mud blockages and flush them so water flows freely. Then disinfect the bathroom. If the pipes stay blocked, the smell will come back.

5. How should the landlord look after the rooms after the service?
Set a cleaning roster for the shared bathroom, ask tenants to air out mattresses regularly, open doors and windows when possible, and watch for black spots on the walls. Act as soon as you see them.

6. Can I treat only the rooms with the strongest smell?
You can, but in a row where walls and pipes are connected, treating the whole row together with the shared areas gives better results, because germs and odor tend to spread between rooms.

7. When can tenants cook and sleep in the room again?
Once the ventilation period the team specifies has passed and there is no ozone smell left, tenants can return to normal use. We recommend wiping down surfaces that touch food, such as tables and shelves, with clean water before cooking, and putting fresh, dry bedding on a raised base rather than straight onto the floor.

8. Does the service need the landlord to be present?
It helps to have the landlord or a trusted representative on site for the survey and at the start of the work, to open rooms, confirm the schedule with tenants and answer questions. After that, the team can work through the rooms according to the agreed plan, and report back once every room has been ventilated and checked.

Make Your Rental Rooms Livable Again and Keep Your Tenants

Talk to the World Health Disinfection team about a room-by-room disinfection and ozone plan that fits your row house.

See Disinfection Service - Click Here

Book Ozone Treatment - Click Here

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

Further Reading

• Residential ozone disinfection
• Ozone treatment for odors and chemical residue
• Mosquito spraying service
• All articles
• External sources: WHO: Floods and health and Thailand Department of Health