Khun Surachai is 49 and manages a frozen seafood processing plant in Mahachai, Samut Sakhon. It has two finished-goods cold stores held at minus 18 degrees and three raw material chill rooms at 0 to 4 degrees.

The plant has held GMP and HACCP certification for twelve years and exports to customers in Japan and Europe, among the most demanding inspection regimes in the world.

In July 2025 the quarterly swab results from the second finished-goods cold store showed total counts above the customer's limit at three of twelve sampling points. The Japanese customer immediately suspended a 6.8 million baht consignment due to ship the following week.

The story

Three points out of twelve that changed everything

Khun Surachai received the results on a Friday afternoon. Within two hours, an email from the Japanese customer arrived suspending acceptance of the consignment due to load the following week.

The three failing points told a very clear story between them: the wall-to-floor junction in a corner of the room, underneath the innermost pallet racking, and around the ducting of the evaporator coil.

What those three had in common was one thing only: in practical terms, nobody can reach them. A corner permanently occupied by stacked pallets, racking that requires a forklift to clear, and ducting nearly four metres up.

What he found hardest, he says, was that his team followed every point of the SSOP cleaning plan without fail and every record was complete. But even the best cleaning plan can only reach where a person can go.

Why cold stores are far harder to clean than ordinary rooms

The food safety consultant the plant brought in explained that a cold store has three constraints that severely limit conventional cleaning.

First, water. Washing in a room at minus 18 is close to impossible, because the water freezes on contact. And in a 0 to 4 degree chill room, wash water raises the humidity, which becomes ice build-up and a fresh reservoir for organisms.

Second, chemicals. Many disinfectants lose substantial efficacy at low temperature, and in food contact areas there are constraints on residue that must be rinsed away with water — which loops straight back to the first problem.

Third, shutting the system down. A deep clean means stopping refrigeration and moving stock out, which is very costly: external cold storage rental, transport, and the risk of the product's temperature changing in transit.

The real cost of a suspended order

The suspended consignment was 6.8 million baht. Khun Surachai says that is only the first number, because the product was already made and sitting in the cold store — every waiting day costs electricity and storage space.

The plant had to commission two rounds of urgent external laboratory retesting at 78,000 baht each, and submit a corrective and preventive action report to the customer within fourteen days.

The customer also cut the following quarter's order volume by 30 percent while assessing the corrective action — roughly another 9 million baht — and increased swab frequency from quarterly to monthly at the plant's expense.

The frightening thing about food export, he says, is that customers do not judge you on twelve good years. They judge you on how well you handled the most recent incident, and on whether your measures are demonstrable.

The method Japanese plants already use

The same consultant suggested he look at ozone in cold stores, saying it is long-established practice in Japanese and European food plants, particularly in areas that cannot be washed with water.

Three reasons make it suit a cold store, and they map exactly onto the three constraints. It is a gas, so it adds no water and creates no ice. It decomposes back into oxygen, so it leaves no residue on food contact surfaces. And it reaches corners, the space under racking and the area around ducting by itself, with nothing moved.

He had the team survey the following week. They assessed each cold store's air volume, adjusted the cycle for the low temperature, and carried out the work on a Sunday night when the plant was closed.

The following week's repeat swabs from all twelve original points passed. When he submitted the report together with the equipment's Department of Medical Sciences certification, the Japanese customer released the suspended consignment within five working days.

What it actually costs

Why the usual fixes fail

10 reasons ozone treatment solves it

1. No water, so no ice build-up and no added humidity

This is the first and most important advantage in a cold store. Ozone is a dry gas, so it works at minus 18 without adding water that becomes ice build-up and a fresh reservoir for organisms.

2. No residue on food contact surfaces

Ozone decomposes back into ordinary oxygen after reacting, so there is no water rinse required and no chemical left on floors, walls, racking or packaging — a core requirement in food storage areas.

3. It reaches corners, under racking and around ducting

Failing swab points are almost always places that cannot be cleaned in practice. Ozone is a gas, so it reaches all of them by itself with no pallets moved and no racking dismantled.

4. No stock movement and no long refrigeration shutdown

Avoiding a move to external cold storage saves transport, rental and the risk of a temperature excursion — costs that are usually many times the service fee.

5. 99.99% removal of embedded mould

Testing confirms 99.99% removal of deep-seated mould in air conditioning systems and furnishings, with virus and bacteria kill an order of magnitude beyond that — the level export customers want to see in a report.

6. It treats the evaporator coil and ducting, a recurring risk point

Evaporator coils condense continuously and produce meltwater on every defrost cycle, making them the most common failing area in a cold store. Running the coil fans during the cycle carries ozone right through that zone.

7. The Master Ozone Generator is certified by the Department of Medical Sciences

WHD uses the Master Ozone Generator, the only ozone brand in Thailand certified by the Department of Medical Sciences, Ministry of Public Health, and tested by Intertek UK — attachable directly to a corrective and preventive action report for an export customer.

8. It can be written into a HACCP control plan as a preventive measure

Rather than an emergency fix, a scheduled ozone cycle in the control plan is a documented preventive measure — precisely what auditors and overseas customers weight most heavily.

9. It runs outside production hours with no line impact

The automatic digital timer cycle runs about thirty minutes; large areas take several consecutive cycles. The team works on a closed shift and the line runs normally the next shift.

10. It works for cold stores, packing rooms and processing areas alike

The same principle applies to raw material prep, wash rooms, packing rooms and changing rooms — the other areas where swab results commonly fail — so one method covers the whole plant.

Before and after

How we get you started, in 3 steps

What a customer says

The most common misconceptions about cold stores

First: cold kills organisms. In fact cold slows growth but does not kill. Several bacteria including Listeria can grow at temperatures near zero, and many organisms simply remain dormant until conditions improve.

Second: cold stores are dry. In fact they carry a continuous moisture cycle from condensation on the evaporator and from meltwater on every defrost cycle. That water is exactly the moisture organisms need.

Third: a clean floor means a clean room. In fact failing swab points are usually not the floor — they are wall-to-floor junctions, under racking, around ducting, and in the door seals, none of which anybody scrubs daily.

Fourth: cleaning more often solves it. If the problem is where people cannot reach, increasing frequency where they can changes nothing about the results at the points they cannot.

What export customers want to see in a corrective action report

Khun Surachai says the most important lesson was not about disinfection method but about what an overseas customer wants to see in a report.

The first thing they want is a credible root cause, not an assurance that you will be more careful. Identifying that all three failing points are physically unreachable is an analysis customers accept immediately.

The second is a corrective measure that matches that root cause. If the cause is that people cannot reach, the measure must be a method that does not require a person to reach — which makes a gas the logically consistent answer.

The third is verifiable evidence: government certification for the equipment, records of the work performed, and repeat swab results from the same points. With all three, the Japanese customer released the consignment in five working days after a three-week suspension.

Frequently asked questions

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