Khun Somporn is 52 and is executive housekeeper at a 180-room hotel in north Pattaya, managing 26 housekeeping staff and a laundry that processes an average of 1.4 tonnes a day — sheets, pillowcases, towels and bath mats.

In the second quarter of 2025 the hotel received 38 guest complaints in three months about musty odour in towels and bed linen — against just 4 complaints in the whole of the previous year.

She audited every stage of the wash process: water temperature, detergent dosing, cycle selection and drying time. Everything met the standard. And when she smelled linen fresh out of the dryer, there was no odour at all.

The story

Linen with no smell leaving the dryer and a smell by the time it reached the room

Khun Somporn ran a simple experiment that answered the question immediately. She took ten towels straight out of the dryer and smelled each one. Nothing. Then she took ten towels off the storage shelving in the same room that had been there three days, and smelled them.

Every single one from the shelf was clearly musty — the same batch, through exactly the same wash and dry process.

She repeated it: she sealed freshly dried towels in a plastic bag and left it in the manager's office, a dry air-conditioned room. Three days later that bag had no odour at all.

Both experiments pointed the same way. The problem was not the wash process and not the linen. It was the air in the laundry and the linen store, where clean linen has to sit before it is used.

Why the laundry is the most humid room in a hotel

The technician the hotel brought in explained that a hotel laundry is the highest-humidity space in the entire building — and usually the one whose ventilation was most under-designed.

Industrial dryers release enormous heat and moisture on every cycle. Washers release steam. The floor is permanently wet. And steam presses put vapour directly into the room.

With inadequate extraction, relative humidity in this hotel's laundry measured 84 percent during the middle of the day with the machines running at full load — well above the level at which mould begins to grow.

The clean linen store adjoined the laundry with no separating door, so humid air flowed into it continuously. Towelling, being the most absorbent cotton in the building, became a sponge taking in both moisture and fungal spores from the air.

The hidden cost behind 38 complaints

Thirty-eight complaints in three months means replacing the guest's linen immediately every time, rewashing the batch, and in many cases offering a discount or a compensatory gesture.

Khun Somporn calculated direct costs from rewashing and compensation at about 210,000 baht over three months. She says that is the smallest number in the story.

The larger cost was reviews. Of the 38 complaints, 14 became online reviews — and 'musty towels' is a phrase bookers weight extremely heavily, because it reads as a statement about the cleanliness of the whole hotel.

The hotel's cleanliness score on booking platforms fell from 8.9 to 7.8 in a single quarter, which the sales team estimated cost about 12 percent of the following quarter's advance bookings.

The fix had to be the air, not the linen

The hotel's first move was two additional extraction fans in the laundry and a dehumidifier in the linen store, at about 320,000 baht. Both were the right thing to do and genuinely reduced humidity.

The odour did not go, because the spores and mould already established on the walls, on the shelving, in the grooves of the stainless steel racks and in the duct work continued releasing into the air. Lowering humidity slows growth; it does not remove what exists.

The consultant recommended ozone treatment of both the laundry and the linen store, explaining that ozone is a gas reaching the walls, the shelving recesses, the ducting and into the linen stored on the shelves simultaneously, without wetting anything and without leaving chemicals.

The team worked on a Tuesday night, the lightest linen volume of the week, taking about two hours for both rooms. The next morning Khun Somporn took towels from the same shelf and smelled them — the first time in four months that stored linen had no odour at all.

What it actually costs

Why the usual fixes fail

10 reasons ozone treatment solves it

1. It treats the room's air, the true source of odour in linen

Clean linen sitting in spore-laden air always reabsorbs. Ozone removes the spores from the air and from the room's surfaces — something no stage of a laundry process can do.

2. It penetrates linen stacked on the shelves without wetting it

Ozone is a gas, so it reaches into the fibres of towels and sheets stacked on shelving, breaking down both the spores and the odour molecules they absorbed — with no rewashing and nothing getting wet.

3. It reaches the grooves and weld seams of stainless shelving

Linen racks have grooves along welds and leg joints that cloths cannot enter but where moisture collects and mould grows well. A gas reaches all of them by itself.

4. It reaches beneath washers and dryers, where nobody ever cleans

The space under floor-mounted industrial machines holds moisture permanently and is never cleaned in the equipment's service life. Ozone spreads in there without moving anything.

5. No chemical residue on linen guests press to their faces

Ozone decomposes back into ordinary oxygen, leaving no deposit or chemical on towels, sheets or bathrobes — the items that touch guests' skin and faces directly.

6. It adds no humidity to the most humid room in the hotel

A laundry can run at 84 percent relative humidity with machines at full load. Any method that adds water or steam makes it worse. Ozone is a dry gas, so it removes organisms without adding moisture.

7. 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 appropriate level for linen used directly on skin.

8. It cuts rewashing costs and extends linen life

Frequent high-temperature rewashing shortens linen life and costs water, power and detergent every time. Fixing the source removes the need to rewash, saving many times the service cost over a year.

9. About thirty minutes per cycle, done outside peak hours

The automatic digital timer cycle runs roughly thirty minutes — two to start, twelve to disperse, twelve to purify, twelve to rest. It is done on the lightest linen night without affecting wash schedules.

10. 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.

Before and after

How we get you started, in 3 steps

What a customer says

Why towelling is the most absorbent odour trap in a hotel

Towelling is engineered to absorb as much water as possible, using a looped cotton structure that multiplies surface area many times over compared with flat cloth. That property is what makes it a good towel — and what makes it an excellent odour sponge.

In air with high humidity and fungal spores, towelling absorbs both extremely efficiently into that looped structure. The better the towel, with denser loops, the more it absorbs.

This is why hotels that invest in expensive high-quality towelling often have more odour trouble than hotels using thinner cloth, when both store linen in the same conditions.

Bathrobes and bath mats are two more items with the same issue for the same reason: thick cotton with very high surface area, usually left on the shelf longer than bed linen.

The checklist every hotel laundry should have

Khun Somporn's current measures come to five points: the first three are one-off structural investments, the last two are routines.

One: install extraction capacity matched to the output of your dryers — the thing most hotels under-specify at the building design stage. Two: fit a separating door between the laundry and the clean linen store. Three: install a dehumidifier in the linen store and target relative humidity below 60 percent.

Four: ozone-treat both rooms monthly as a routine, to remove the spores and mould accumulating on walls, shelving, ducting and in the stored linen itself.

Five: have someone who has just walked in from outside smell linen from the shelf every week — not someone who works in the laundry all day, because their nose adapts and stops registering the smell within minutes.

Frequently asked questions

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