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

The water is gone, but the settle plates in the filling room still fail

A mid-sized contract manufacturer in an industrial estate in Pathum Thani makes supplement capsules, skin creams and a handful of household medicines under GMP. During the flood season, water from the canals surrounding the estate pushed into the building to a depth of about forty centimetres and stayed for almost two weeks. The team managed to lift some raw materials onto the mezzanine in time, but the raw material warehouse, the weighing room, the corridor outside the production suites and the ground-floor plant room housing the air handling units (AHUs) all sat under murky water carrying mud, debris and sewage that had backed up through the floor drains.

Nok, the head of quality assurance, told the recovery meeting that everyone had done what they were supposed to do. They shovelled out the mud, scrubbed the floors, washed down the sandwich-panel walls and wiped every room with the plant's approved disinfectants according to the standard procedures. Yet when quality control placed open settle plates at the environmental monitoring points, mold colonies came back above the action level at several locations, particularly near the supply air diffusers and along the corridor that connects to the warehouse. At the same time, staff began to complain about a damp, musty smell drifting from the ceiling void and the return air grilles.

Management asked the one question everybody dreaded: "When can we start producing again?" Orders from several contract customers were waiting. QA knew that restarting before the environment met its limits was not a paperwork risk. It was a real risk of microbially contaminated product, recalls and the loss of trust that had taken years to build. This is the moment when many plants realise that washing a room until it looks clean and restoring a production area to a microbiologically safe condition are two very different things.

Why a flood hits GMP plants so hard

Good Manufacturing Practice, whether it applies to medicines, cosmetics or dietary supplements, has one core idea: control every factor that could make a product unsafe or out of specification. That includes the building, the environment, the air, the water, the people and the materials. A flood breaks all of those controls at once. Flood water is not clean water. It carries microorganisms from soil, drains and sewage into contact with floors, walls, table legs, machine bases and every crevice that was designed to be easy to clean only under dry conditions.

The organisms QA teams should watch

Molds such as Aspergillus and Penicillium. These are everyday molds of soil and dust. When indoor humidity stays high for days, their spores germinate on anything with organic content: corrugated cartons, wooden pallets, pipe insulation, pre-filters and gypsum ceiling boards. Huge numbers of spores are then carried through the air handling system and settle onto surfaces in production rooms. Mold is a particular concern for powders and capsules, because even a slight rise in moisture can support growth, and it is a common reason for failing total yeast and mold counts.

Water-loving Gram-negative bacteria. Groups such as Pseudomonas and the Burkholderia cepacia complex are well known in pharmaceutical and cosmetic manufacturing because they survive for long periods in water and damp places and have been behind recalls of water-based products in many countries. After a flood they can settle into floor drains, gutters, holding tanks and joints in water systems that were submerged. Plants making creams, lotions, shampoos or oral liquids need to treat this risk very seriously.

Faecal bacteria from sewage. E. coli and other enteric bacteria should never be found in products that are swallowed or applied to the body. When sewage has backed up into the building, every surface that touched the water should be assumed to carry them until it has been properly cleaned and disinfected. Soil and mud also bring spore-forming bacteria such as Bacillus, which tolerate harsh conditions and some disinfectants better than ordinary bacteria.

How contamination spreads through the plant after the water recedes

The first route is direct contact: epoxy floors, the lower part of walls, door frames, the space under cabinets and machine plinths. The second route is air, and it is the one most often overlooked. A flooded AHU room, return ducts, internal duct lining and wet pre-filters become mold incubators that push spores into every room the system serves, including rooms that never saw a drop of flood water. The third route is people and things: staff walking from dirty zones into clean zones, trolleys, pallets and packaging cartons that were once damp. The last route is water. If the flood reached pumps, storage tanks or feed points, the whole purified water system needs to be reassessed before it is trusted again.

Who is most at risk

On the human side, the workers who shovel mud and tear out wet materials inhale the largest doses of mold spores. People with allergies, asthma or chronic illness may develop coughing, chest tightness, a blocked nose or itchy rashes. Pregnant women and people with weakened immunity should avoid working in freshly flooded areas. Anyone who waded through flood water and then develops fever, headache or calf pain should see a doctor promptly and mention the flood exposure, because these can be early signs of leptospirosis. On the product side, the most vulnerable end users are young children, older adults, patients and people with weakened immune systems, who are also the heaviest users of medicines and supplements. One contaminated batch reaches exactly the people least able to cope with it.

What an incomplete recovery really costs

Consumer health and safety. Products with microbial counts above limits can cause skin, eye or gastrointestinal infections, especially among high-risk users. Some organisms also cause discoloration, off-odours, phase separation or early spoilage well before the labelled expiry date.

Money. The damage does not end with the soaked raw materials. It includes quarantined stock waiting for results, repeat testing, replacement filters, HVAC repairs, overtime and penalties for late delivery. If a product has to be recalled from the market, the cost multiplies: reverse logistics, destruction and a great deal of communication with partners and regulators.

Time. Every day a line stays down is a day a competitor can take the work. Many contract manufacturers lose customers not because of the flood itself, but because recovery was slow and they could not demonstrate that the production environment was safe again.

Reputation and regulatory standing. A certified plant has to show that it handled an abnormal event systematically: a deviation record, a risk assessment, corrective and preventive actions (CAPA) and environmental monitoring results before restart. If an inspector or a customer auditor later finds gaps, the damage to credibility can outlast the flood by years.

Employees and their families. Many staff will have flooded homes too. The strain of restoring a house and a workplace at the same time, and the worry about whether their jobs are secure, is real. A fast and safe recovery is also a way of looking after the people who run the plant.

Why the usual fixes fall short

Wiping only the surfaces you can see. Plant disinfectants work well when they contact microorganisms directly for the specified time. After a flood, however, much of the contamination hides where a cloth cannot reach: the ceiling void, joints between wall panels, cable trays, the back of control cabinets and inside ducts. Wiping reduces the load on the surface but leaves the reservoirs that will reseed it.

Using strong bleach on everything. Chlorine has a place on certain hard surfaces, but excessive concentrations corrode stainless steel, damage grout, leave odours and residues, and lose much of their power in the presence of mud and organic soil. Bleach also cannot rise into the air or penetrate closed voids.

Switching on fans and the air conditioning to dry things out. Drying is essential, but running an AHU that was submerged, without cleaning it and changing its filters first, simply blows mold spores through the whole building and contaminates rooms that were never flooded.

Painting or coating over mold stains. Covering the marks may make a room look ready for inspection, but mold under the paint is still alive. It will return as black spots or musty odours within weeks. Worse, it invites auditors to question the transparency of the whole recovery.

Masking odours with air freshener. In a cosmetics or supplement plant, fragrance from a spray can itself become a contaminant, and it does nothing about the microbes that create the smell in the first place.

WHD ozone disinfection: a supporting step that helps production areas recover faster

The Residential and Building Ozone Disinfection service from World Health Disinfection (WHD) covers homes, condominiums, hotels, offices, schools, hospitals and factories. Ozone (O3) is a strongly oxidising gas. Released into a closed space, it spreads in every direction, including corners, ceiling voids and places that no cloth can reach. It attacks the cell structures of viruses, bacteria and molds and breaks down odour-causing molecules, then reverts to ordinary oxygen (O2) without leaving chemical residue. That last property matters in a GMP environment where every possible contaminant has to be controlled.

According to the test results certified for the company, the WHD ozone system has been tested and certified by Thailand's Department of Medical Sciences and by Intertek (UK) as eliminating 99.99% of viruses, bacteria and mold. You can review the documents on the certification page.

Let us be clear from the start. Ozone treatment is a supporting step. It does not replace mud removal, washing, drying, replacing damaged materials, or the plant's own validated cleaning and sanitisation procedures. It does not replace environmental monitoring or QA's release decision. What ozone does is deal with the microorganisms in the air and in hard-to-reach voids, so that the next round of environmental monitoring has a better chance of meeting its limits.

How the work is carried out in a factory

1. Survey and zoning. The WHD team walks the site with engineering and QA, dividing the building by cleanliness grade and by HVAC zone, and identifying flooded rooms, rooms that share air with them and places with musty odours.
2. Remove or seal all materials and products. Ozone is an oxidiser, so it should not contact raw materials, active ingredients, extracts, fragrances, primary packaging or finished goods. Everything is moved out or kept in sealed containers as QA specifies.
3. Confirm the area has been cleaned and dried. Mud removal, washing and drying must already be complete. Absorbent materials that were damaged, such as swollen ceiling boards, wet insulation and pre-filters, should be removed and replaced first.
4. Close the space: no people, pets or plants. Every room to be treated must be empty. Doors are closed, "no entry" signs posted and access controlled together with the plant's safety officer.
5. Fill the space with ozone. Equipment is matched to room volume. A typical cycle takes about 30 minutes per zone depending on size and condition, and it can be planned with engineering so that air recirculates inside the zone and ozone reaches the ductwork.
6. Contact time. The ozone is left to react with microorganisms and odour molecules for the specified period.
7. Rest and ventilate. The area is left to allow ozone to revert to oxygen and is then ventilated for the time the team advises before anyone is allowed back in.
8. Hand over to QA. The plant runs its own environmental monitoring, such as settle plates, active air sampling and surface swabs, to support its restart decision.

10 reasons pharmaceutical, cosmetic and supplement plants choose ozone after a flood

1. It reaches places hands cannot. Ozone gas moves into ceiling voids, panel joints and the space behind machines, where post-flood mold typically hides.
2. No chemical residue. Ozone reverts to oxygen, so it leaves nothing behind that could contaminate a production area. Read more about ozone and chemical residue.
3. It reduces airborne microbes, the route by which mold spores land on surfaces inside clean rooms.
4. It breaks down musty odours at the source rather than masking them, which matters in cosmetic plants where foreign odours can affect products.
5. Tested by credible bodies, according to the test results certified for the company by the Department of Medical Sciences and Intertek (UK).
6. Zone-by-zone scheduling lets engineering bring ready areas back into use first, instead of waiting for the whole site.
7. Short cycles. Around 30 minutes per zone plus a rest period makes the restart plan easier to predict.
8. Scales to large spaces, from raw material stores and corridors to changing rooms and site offices, through our building ozone disinfection service.
9. Works alongside other disinfection. Use it together with the plant's approved surface disinfectants. Ozone jobs of 15,000 baht or more also receive a free medical-grade disinfectant spray.
10. Supports your documentation. The team records dates, areas and steps performed so QA can reference them in the deviation and CAPA file. Ask for details on the ozone service page.

Example case: a cream and supplement contract manufacturer in Nonthaburi

Example case (an illustrative scenario to explain the process, not a verified review)

Ae manages a small contract manufacturing plant in Nonthaburi. Only the ground floor, which holds the warehouse and plant room, was flooded. The cream production suite is on the first floor, so the team first assumed it was unaffected because the water never reached it. Environmental monitoring told a different story: mold counts upstairs were higher than normal, because the entire building was served by a single AHU located on the ground floor.

The plant worked in this order. It stopped the air handling system, removed wet pre-filters and duct insulation, and had its HVAC contractor clean the coils and drain pans. It washed the warehouse and dried it with dehumidifiers. It moved all raw materials and packaging out. Only then did it book the WHD team to treat the building zone by zone, starting with the plant room and warehouse, then the corridors and finally the production suite. After the rest and ventilation periods, QC repeated environmental monitoring according to its plan.

Ae's main lesson was simple: "The problem is not just the rooms that flooded. It is every room that shares the same air." Working in a clear sequence also meant that everyone knew which zone would be ready on which day, which cut confusion and avoided repeat work.

GMP plant flood recovery checklist

Phase 1: Safety and assessment

• Isolate power to flooded zones and have an electrician inspect before re-energising.
• Wear boots, rubber gloves, a mask and eye protection while removing mud.
• Open a deviation and risk assessment on day one. Photograph water levels and damage as evidence.
• Quarantine raw materials, packaging and products that may have contacted water or high humidity until they are assessed.

Phase 2: Remove, clean and dry

• Remove absorbent materials such as swollen ceiling boards, insulation, cartons and wet wooden pallets.
• Clean hard surfaces with detergent first, then disinfect according to your standard procedures.
• Use dehumidifiers and ventilation, following the general public health advice to clean and dry within 24 to 48 hours to limit mold growth.
• Stop any HVAC system that was flooded; clean the AHU, change filters and inspect ducts before restarting.
• Assess the water system with engineering, including pumps, tanks and pipework, before returning it to use.

Phase 3: Before ozone day

• Move raw materials, products and packaging out, or seal them as QA requires.
• Ask the team about materials that are sensitive to oxidisers, such as some rubbers, and equipment the manufacturer recommends protecting.
• Brief every shift on the closure times and make sure everyone leaves the treated zone.

Phase 4: After ozone

• Re-enter only after the rest and ventilation period the team specifies.
• Run environmental monitoring according to your plan and clean product-contact surfaces as per procedure before production.
• Close the deviation with preventive actions, such as raising critical equipment or installing flood barriers.
• Watch staff health. Fever, calf pain, diarrhoea or a persistent cough means a visit to the doctor.

Frequently asked questions

1. Can we restart production right after ozone treatment?

Ozone alone should not be the basis for that decision. Restart belongs to QA and should rest on environmental monitoring results, the state of the water and air systems, and equipment cleaning according to your procedures. Ozone is one of the steps that gives the area a better chance of passing.

2. Do we really have to move all raw materials and products out?

They should be removed or tightly sealed. Ozone is an oxidiser and can react with active ingredients, essential oils, extracts and some packaging. Protecting materials is a core condition of the job.

3. Can staff keep working in other zones during treatment?

Yes, if those zones are clearly separated and do not share air handling with the zone being treated. The treated zone itself must be empty of people, pets and plants and may only be re-entered after the rest period.

4. How long does it take?

Typically about 30 minutes per zone, not including preparation and the rest and ventilation period. Large plants are usually treated in several zones in sequence.

5. Can ozone replace changing HVAC filters or cleaning ducts?

No. Wet or moldy filters must be replaced, and submerged HVAC components must be cleaned by specialists first. Ozone then helps deal with what remains in the space and in the air.

6. Do you have documents supporting the test results?

Yes. The company holds certification from the Department of Medical Sciences and Intertek (UK), available on the certification page of the website. Results in your own plant should still be confirmed by your environmental monitoring.

7. A worker who helped clear mud now has a fever. What should we do?

Send them to a doctor straight away and make sure they mention the flood exposure, especially with high fever, headache or calf pain, which may point to leptospirosis. Ozone treats spaces, not people.

Do not let invisible microbes keep your line down longer than necessary

Talk to WHD about a zone-by-zone ozone plan that fits your plant's recovery schedule.

Request a Factory Ozone Consultation

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

Related services and reading

• Residential and Building Ozone Disinfection
• How ozone helps reduce chemical residue
• Full disinfection services
• Certification documents

References

• CDC: Floods and Your Health
• World Health Organization fact sheets