A Swim School Closed 16 Days to Repaint, Reopened to Red-Eyed Children, and Lost 41 Families to Indoor Pool Paint Smell

When a pool sits inside a sealed building, indoor pool paint smell does not blow away. It mixes with chlorine odour and hangs a few centimetres above the water, exactly where children breathe. Here is what that smell really is, how to fix the source, and how ozone treatment for paint odour handles what is left behind.

A Brand New Blue Pool, and a Smell That Kept 312 Children Out of the Water

This story is a composite based on situations we commonly see; names and places are fictional.

An indoor pool paint smell problem rarely starts with carelessness. It usually starts with someone wanting the pool to look cleaner and safer. Wannisa, known to every parent as "Kru Nam Wan", is 38 and has run Ban Pladao Swim School on the western edge of Bangkok for eleven years, together with her husband "Coach Poom", who handles the older squad classes.

The pool building is a steel-roofed hall about seven metres high. Almost every wall is fixed glass, because the school sits inside a housing estate and needs to keep noise in and rain out. Inside there is a 20 x 10 metre main pool and a 6 x 4 metre toddler pool.

Beside the hall is a glass-walled waiting room with 30 seats, fabric sofas and curtains. The pool hall itself relies on four wall-mounted extract fans as its main ventilation.

Before the shutdown the school had 312 students, from parent-and-baby classes at one year old up to upper-primary swimmers, plus nine coaches. It taught Tuesday through Sunday and closed on Mondays.

Days 1 to 9: grinding the shell, painting the pool, the walls and the roof steel

After eleven years the pool finish was flaking in sheets and algae was staining the coping. Kru Nam Wan used the October school break to close for 16 days. The contractor drained the pool, ground back the surface and applied two coats of chlorinated rubber pool paint in a bright blue.

The hall walls were repainted in an anti-mould white, and the steel roof structure was primed with anti-rust paint and topcoated in oil-based enamel. The total budget was 480,000 baht, part of it a business loan with monthly repayments.

Days 10 to 15: every door shut while the paint cured

The contractor was firm that the pool coating had to dry and cure for the time the manufacturer specified before any water went in. It rained almost every afternoon that week, so the crew closed every door and switched off all four extract fans, afraid that wind-blown rain and dust would settle on paint that had not hardened.

Kru Nam Wan dropped in each evening. A sharp, thinner-like smell sat in the hall and stung her nose, but she assumed that once the pool was filled, chlorinated and the fans were back on, it would clear by itself.

On day 15 the pool technician filled roughly 240 cubic metres of water, then chlorinated and balanced it as usual. Nobody noticed that two of the four extract fans no longer started when the switch was thrown.

Day 16: the Saturday morning class that finished early

At 08:00 on Saturday, eight parent-and-baby pairs walked into the hall. The first mother stopped in the doorway and asked whether the place had just been painted. What met them was not the pool smell everyone knew, but a sharp paint odour layered over chlorine that bit at the nose from the first step.

The 45-minute class ended after 25 minutes, because three toddlers cried and would not stop rubbing their eyes. Two mothers took their children home without waiting to change.

The 10:00 class for five to seven year olds went worse. Khao Hom, a six-year-old with asthma, swam about 20 minutes before starting a tight, repeating cough, and her mother had to bring her out to use her inhaler. Several other children had visibly red eyes. By mid-afternoon Coach Bank, who had stood teaching in the water for six hours straight, went home with a headache and nausea.

Saturday night: the parents' LINE group

The school's parent group on LINE has about 240 members. That night one mother posted a photo of her red-eyed daughter and said the child had been coughing on and off since they got home.

Within two hours there were dozens of replies. Some asked outright whether pool paint is safe for children. By Sunday morning, 19 families had already messaged to say they were pausing lessons.

Two weeks later: 41 families had stopped coming

• In week one, 27 families paused lessons until the smell was gone.
• By the end of week two the number reached 41 families, and 9 asked for a refund on their 12-lesson course.
• November trial-class bookings fell from 38 to 6.
• A swim assessment day for 70 children was postponed indefinitely.

One evening Kru Nam Wan told Coach Poom she would rather have left the paint flaking than watch children climb out of the water with red eyes.

Indoor Pool Paint Smell Mixed With Chlorine Costs More Than You Think

For a swim school, what is actually being sold is a safe experience for somebody's child. When an indoor pool paint smell lingers, the damage arrives on at least four fronts at once.

1. Health: swimmers breathe hard, and they breathe low

A person swimming breathes faster and deeper than someone sitting still, and does it only a few centimetres above the water — the layer where vapours tend to collect in a poorly ventilated pool hall. Common effects of solvent vapour exposure in an enclosed space include:

• Stinging, red or watering eyes, which at a pool is almost always blamed on chlorine alone
• Nose and throat irritation, and coughing
• Headache, dizziness and nausea, especially after long periods inside
• Asthma or allergy flare-ups in people who already have them

The people who need the most care are babies and toddlers in parent-and-baby classes, asthmatic children, pregnant mothers, older adults and anyone with a respiratory condition. Coaches, who spend hours a day in the hall, get the longest continuous exposure of all. Long-term exposure to certain VOCs is also a recognised indoor air quality concern for environmental health agencies.

2. Money: empty lanes, refunds and a renovation loan

• Refunds to 9 families, plus lost revenue from the other 32 who paused
• Lost trial classes, which are the school's main source of new students after a school break
• Loan repayments on the 480,000 baht renovation, due every month whether classes run or not

3. Reputation: the message outlives the smell

Parents choose a swim school almost entirely on word of mouth, in estate groups and young-parent chats. Within five kilometres there are two other swim schools ready to take new students immediately.

One sentence — "that pool reeks of paint, my child came home with red eyes" — can be forwarded for months after the air itself has cleared.

4. Trust: parents, coaches and the children themselves

• Parents start to wonder whether the school knew this smell could affect children, and why it reopened anyway
• Some children now associate the water with stinging eyes and become afraid of it again, after months of coaching to build confidence
• An eleven-year relationship with families who sent one sibling after another wobbled in under a month

What Is That Sharp Smell in a Pool Hall, Really?

What parents summed up as "paint and chlorine" was in fact three problems stacked on top of each other.

Layer 1: solvents from the pool coating and the anti-rust paint

Chlorinated rubber pool paints, along with many anti-rust primers and oil-based enamels, rely on solvents to flow smoothly and bond to the surface. Once applied, those solvents evaporate as volatile organic compounds (VOCs), and that is the source of the thinner-like sharpness.

Evaporation does not stop on the day the paint is dry to the touch. Vapour keeps being released for days or weeks, depending on the coating, the film thickness, the temperature and the ventilation.

Layer 2: the "chlorine smell" that is usually chloramines

Many people assume a strong chlorine smell means a clean pool. In an indoor pool, the sharp, eye-stinging odour usually comes from chloramines, formed when chlorine reacts with sweat, sunscreen and other residues swimmers bring into the water. If the water chemistry is out of balance or the air is not exchanged often enough, chloramines build up right above the surface and the smell gets stronger.

Layer 3: warm humid air in a sealed building, and materials that soak it up

An indoor pool hall is warm and humid all day. Heat speeds up evaporation, while fixed glass walls and switched-off fans leave the vapour nowhere to go. Over six days of closed doors, solvent vapour worked its way into porous materials, including:

• More than 120 foam boards and pool noodles used for teaching
• The fabric sofas and curtains in the parents' waiting room
• Gypsum ceiling panels, changing-room curtains and stored towels

This is off-gassing. Run the fans during the day and the smell fades; close the building overnight and the materials release it again, so it is waiting for you the next morning.

Why the Usual Fixes Do Not Clear Indoor Pool Paint Smell

1. Opening up and adding industrial fans. Kru Nam Wan bought six of them. They helped a little, but airing out takes days to weeks, and moving air never reached the underside of a seven-metre roof.
2. Eucalyptus air freshener. Fragrance masks odour, it does not break down VOCs. Several parents said the combined smell made them feel worse, not better.
3. Bamboo charcoal bags and baking soda. Their adsorption capacity is tiny compared with a hall holding roughly 4,000 cubic metres of air.
4. A home air purifier in the waiting room. Designed for small rooms, its filter saturates quickly, and it does nothing at all for the pool hall.
5. Adding more chlorine. Dosing without testing can increase irritation and does nothing for paint odour. Water chemistry belongs with a qualified pool operator.
6. Waiting it out. Porous materials keep re-releasing odour, while parents do not wait and the business loses bookings every day.

The Fix: Control the Source First, Then Ozone Treatment With the Master Ozone Generator

Once the pool technician had rebalanced the water and replaced two failed fan motors, the chlorine smell eased — but the indoor pool paint smell was still sitting in the waiting room and in the foam boards. That is when Kru Nam Wan contacted WHD's ozone paint odour and chemical residue removal service.

How ozone works

The Master Ozone Generator releases ozone gas (O₃), imitating the way nature purifies air. Ozone oxidises and breaks the molecular bonds of odour molecules, chemical vapours (VOCs) and germs at the source, so the odour is destroyed rather than covered. The ozone then decomposes naturally back into oxygen (O₂), leaving no chemical residue.

Because it is a gas, ozone spreads across a large volume, reaches up into high roof structures and gets into corners no cloth or fan will ever touch.

Measured with real TVOC readings on site

WHD measures TVOC (Total Volatile Organic Compounds) before and after treatment with an AM1310 meter, backed by calibration paperwork (a KIMO PT100 SC0110 adjusting certificate and a BR-SMART certificate of calibration). WHD is one of the few providers in Thailand that shows TVOC reduction measured at real job sites, which means parents can be shown numbers instead of a promise that the smell is gone.

Fast: usable again within about two hours

After the cycle and ventilation, a treated area is generally ready to use within about two hours. The school was able to fit the whole job into its regular Monday closure, without shutting down for extra days.

10 Reasons an Indoor Swim School Should Choose Ozone Treatment From WHD

1. It destroys odour at the source instead of masking it

Ozone breaks down odour molecules and chemical vapour, unlike fragrance, which simply adds something new to the air children have to breathe.

2. Suited to a high-roofed pool hall

The Master Ozone Generator ozone treatment covers large volumes and reaches the freshly painted roof steel that floor fans never touch.

3. It reaches the materials holding the smell

Foam boards, sofas and curtains are treated at the same time, which reduces the odour that comes back out of them the following morning.

4. Before and after TVOC results

An ozone treatment that reduces TVOC levels gives a school something straightforward to show worried parents.

5. No chemical residue left behind

Ozone decomposes back into oxygen. It leaves no film and no new smell on the pool coping, the benches or the toys in the water.

6. Done inside one closed day

Areas are generally usable again within about two hours after the cycle, so no additional classes have to be cancelled.

7. Planned alongside your pool operator

The team coordinates on how the water surface is handled during treatment, and recommends a final water check before swimming resumes.

8. Trained technicians, safety at every step

People are cleared out, the building is closed off, warning signage goes up, and the area is checked before it is handed back.

9. Every zone of the school, not just the pool

The chemical residue removal service covers the hall, the waiting room and the store rooms, and helps with musty odours and mould in enclosed spaces too.

10. Experience across very different sites

From condo bedrooms and office meeting rooms to car paint spraying and chemical plants — and the team is easy to reach by phone or LINE.

Before / After at Ban Pladao

How the WHD Team Works

1. Site survey and baseline TVOC reading with the AM1310 meter at several points — above the pool coping, in the waiting room and in the changing rooms — along with questions about which coatings were used.
2. All people, pets and plants out. Items sensitive to ozone, such as artwork, natural rubber goods and electronics, are moved or covered, and the handling of the water surface is planned with the pool operator.
3. Close off the area and set up the Master Ozone Generator. Doors, fans and air conditioning are shut down and warning signs go up.
4. Run a cycle sized to the volume of the space, treating the main hall and the smaller rooms separately where that makes sense.
5. Allow the ozone to decompose and ventilate the space before anyone is allowed back in.
6. Re-measure TVOC and re-check odour at the same points, so before and after can be compared honestly.
7. Hand the space back, generally usable within about two hours, with a recommendation to check the water again before swimming resumes.

How the Story Ended: Noise and Laughter Back in the Saturday Class

On the Monday closure the WHD team arrived early. Foam boards were spread out around the pool, sofa cushions were stood upright, and the pool operator covered the water surface as planned. After the cycle and ventilation, repeat TVOC readings were lower at every measuring point, and the waiting room smelled clearly better.

That evening Kru Nam Wan posted in the parents' group. She explained plainly where the smell had come from, said the water and the fans had been fixed, attached the before and after readings, and offered two make-up lessons to every child who had missed classes.

Seventeen families came back in the first week. Within a month, around 30 of the 41 had resumed lessons; the nine who had already taken refunds did not return. Khao Hom came back for a short class with her mother watching from the poolside, and finished it in the water.

How to Avoid Indoor Pool Paint Smell Next Time You Renovate

• Ask what solvent system every coating uses, and choose lower-VOC products wherever they are suitable, such as walls and ceilings.
• Allow the full cure time stated by the manufacturer. Do not rush filling the pool or reopening.
• Test the extract fans before work starts, and ventilate while the coating cures instead of sealing the building shut.
• Move foam boards, cushions and curtains out of the building during painting, and have the pool operator balance the water before opening day.
• Book ozone treatment and a TVOC check one or two days before you reopen, and tell parents the plan in advance.

Frequently Asked Questions

Q: Does everyone have to leave during ozone treatment?
A: Yes. People, pets and plants must stay outside the treated area for the whole cycle, and re-entry happens only after the team has confirmed the ozone has decomposed and the space has been ventilated.

Q: How long does it take?
A: It depends on the size of the space and how strong the odour is. After the cycle, an area is generally usable within about two hours, which is why a single closed day is usually enough.

Q: Does ozone leave a residue?
A: Ozone decomposes naturally back into oxygen, so no chemical residue is left behind. The team only hands the space back after the decomposition and ventilation stage.

Q: What size of space is this suitable for?
A: Anything from a condo bedroom to large volumes such as a pool hall, a meeting room or a factory floor. The cycle is calculated from the actual volume.

Q: Will the chlorine smell go away too?
A: Treatment reduces odour that has built up in the air and in materials, but if the water is unbalanced or ventilation is inadequate, that smell will form again. Water chemistry and airflow have to be managed alongside it.

Q: Is this the same as an ozone water treatment system?
A: No. This service treats the air in an empty building to break down residual odour and vapour. It is not a water sanitation system in the filtration plant.

Read More

• Ozone cleaning service
• Residential ozone disinfection
• Disinfection spraying service
• US EPA: VOCs and indoor air quality
• WHO: air quality and health

Do Not Let Paint Odour Teach Children to Fear the Water

Talk to the WHD team about ozone treatment for paint odour and residual chemical vapour, with before and after TVOC readings taken at your own site.

Tel 065-556-6294 · LINE @whd268 · worldhealthdisinfection@gmail.com
88/268 Kalpapruek Road, Bang Khae, Bangkok 10160