A 60-Room Hotel with 17 One-Star Reviews Saying the Same Thing: The Room Smells Musty. Score Fell 8.7 to 7.1
Last updated: 6 Sep 2026 | 8 Views |
Ozone disinfection service 2026 for hotels, resorts and accommodation
A 60-Room Hotel with 17 One-Star Reviews Saying the Same Thing: The Room Smells Musty. Score Fell 8.7 to 7.1
Why musty guest rooms are the most damaging review a hotel can get, and why however well housekeeping cleans, it is not enough.
In the hotel business, the phrase 'musty smell' in a review carries more weight than 'small room' or even 'unhelpful staff', because it speaks to cleanliness — the one thing guests will not forgive. This is the true story of a sixty-room hotel whose score fell 1.6 points in a single high season.
Every hotel has a detailed room cleaning system: linen changed daily, carpets vacuumed, surfaces wiped, bathrooms cleaned, and every room checked by a supervisor before sale. Most hotels do all of this well.
But that entire system addresses surfaces, while musty guest room odour comes from three places housekeeping cannot reach: inside the air conditioning box, inside the mattress and sofa foam, and in the lower layer of the carpet.
This article tells the true story of a sixty-room hotel that received seventeen one-star reviews about smell in a single high season, explains why ozone treatment handles it in thirty minutes per room, and why several five-star chains already use exactly this method.
The story
The older wing nobody suspected
Weeraya is general manager of a sixty-room hotel in a tourist town. The building has two wings: a newer wing of thirty-two rooms built six years ago, and an older wing of twenty-eight rooms in the original eighteen-year-old building.
Both wings use the same housekeeping team, the same cleaning standard, and the same room inspection before sale.
That high season the hotel was nearly full every night, and Weeraya began noticing one- and two-star reviews arriving unusually often.
Reading back through them, she found seventeen reviews mentioning the same thing: a musty or damp smell in the room. Cross-checking the room numbers, fifteen of the seventeen were in the older wing.
A score that fell from 8.7 to 7.1
Over one high season the hotel's overall score on its main booking platform fell from 8.7 to 7.1 — an unusually steep drop for a hotel that had changed nothing about its service.
The consequence was structural, because booking platforms use review scores to rank listings. A hotel that falls below 7.5 is displayed noticeably lower in search results.
Bookings over the following two months fell by about twenty-two per cent. And when Weeraya tried cutting older-wing room rates by 300 baht a night to stimulate demand, she attracted a more price-sensitive segment that wrote more negative reviews than before.
In money terms, the lost bookings over those two months came to about 1,400,000 baht — and the fallen score kept affecting rankings for months afterwards.
What housekeeping was already doing, and why it was not enough
Weeraya called a housekeeping meeting and reviewed every step of the process. What she found was a team doing excellent work with no step missing.
Bed linen and pillowcases changed daily, towels changed daily, every room's carpet vacuumed, bathrooms cleaned and grout scrubbed, all surfaces wiped, and every room inspected by the supervisor before sale.
She added curtain washing every three months, mattress protector washing every month, a small air purifier in each older-wing room, and air conditioning servicing every three months instead of every six.
Three months later, reviews about smell were still coming. Slightly fewer, but still there. And when she sat in an older-wing room that had been closed for two days and switched on the air conditioning, she smelled it herself within the first minute.
What the big chains had been doing all along
Weeraya spoke to the executive housekeeper of a large hotel chain she knew through an industry association, and got an answer that explained why those hotels did not have this problem.
That chain ozone-treated guest rooms on a standing cycle: rooms vacant more than three days, rooms reported for smell after checkout, and every floor on a quarterly rotation.
Their reasoning was that musty guest room odour does not come from visible dirt. It comes from mould and bacteria in the air conditioning box, in the mattress foam, and in the lower layer of the carpet — three places standard cleaning cannot reach at all.
Weeraya started with all twenty-eight older-wing rooms, about thirty minutes each, several rooms a day in the vacant window between checkout and check-in. She inspected them herself the next day. The smell was completely gone.
What it actually costs
'Musty' in a review damages a hotel more than any other word
Guests forgive a small room, a poor view, even insufficient parking. 'Musty' speaks directly to cleanliness, and readers use it to strike a hotel off their list immediately.
A fallen score damages your ranking on booking platforms
Booking platforms rank listings by review score. Falling from 8.7 to 7.1 does not merely make readers hesitate; it pushes the hotel down in search results — a structural consequence.
Discounting attracts guests who write more negative reviews
When a hotel cuts rates to stimulate demand, the guests it attracts are more price-sensitive with different expectations, and in practice tend to write more negative reviews — making the problem worse rather than better.
Housekeeping works harder without fixing anything
When a manager adds steps, the team genuinely works harder with no change in outcome, because the problem is not on the surfaces they can clean — which needlessly damages team morale.
Why the usual fixes fail
Changing linen and washing everything more often
Daily linen changes and monthly mattress protector washing are correct standards. But musty odour comes from the foam inside the mattress, which cannot be washed, and from the air conditioning box, which has nothing to do with fabric.
Vacuuming carpets every day
Vacuuming collects surface dust well, but musty odour accumulates in the lower layer of the carpet and the underlay, where a vacuum cannot reach — particularly in rooms that have had moisture from a dripping air conditioner or a leak.
Servicing the air conditioning every 3 months instead of 6
More frequent servicing helps and should be done. But standard servicing addresses the coil and the filter, while mould also sits in the ductwork, the casing and the insulation, which cannot be stripped out.
Installing air purifiers in the rooms
An air purifier genuinely filters particles from air that passes through it. It does not address the cause embedded in materials — switch it off, or let a guest switch on the air conditioning, and the smell comes out of the box as before.
Spraying air freshener before guests arrive
Freshener masks the smell for a few hours, and the guest arriving afterwards gets fragrance mixed with mustiness — which in reviews is usually described as the hotel trying to cover something up. Worse than the original.
Three places housekeeping cannot reach, and ozone can
The first is the air conditioning box: dark, wetted by condensation every time the unit runs, and accumulating dust — everything mould needs, and beyond the reach of ordinary servicing.
The second is the foam inside mattresses and sofa cushions, which absorbs moisture from the air and from the people lying on it, then releases odour when compressed or when the room warms. The third is the lower layer of the carpet and its underlay.
Ozone is a gas, so it penetrates all three — which a cloth, a vacuum cleaner and an air purifier cannot. World Health Disinfection's ozone service uses the Master Ozone Generator, the only brand in Thailand certified by the Department of Medical Sciences, Ministry of Public Health, and tested by Intertek in the UK at 99.99 per cent effectiveness against mould.
10 reasons the AIROFOG U260 solves it
1. Ozone reaches the air conditioning, the mattress and the carpet underlay at once
These three are the real sources of guest room odour, and the three places the cleaning standard cannot reach at all. One ozone cycle treats all three together without dismantling anything.
2. It addresses the mould that is the cause, not just the smell
The Master Ozone Generator is certified by the Department of Medical Sciences as removing deep-seated mould in air conditioning and furniture to 99.99 per cent — so the smell does not return, because the cause is gone.
3. It runs in the vacant window between checkout and check-in
Rooms are vacant between midday and mid-afternoon at every hotel. The treatment takes about thirty minutes plus ventilation, so it happens without taking rooms out of sale and without affecting occupancy.
4. It adds no humidity to the room
Unlike steam treatment or liquid spraying, ozone is a gas and does not dampen mattresses, carpets or curtains — which matters greatly in a hotel, because added moisture is where the same problem begins again.
5. No residue, so guests can check in immediately after ventilation
Ozone reverts to oxygen after reacting, leaving no chemical residue on mattresses, towels or surfaces guests touch — a necessary condition in a guest room.
6. It handles every hotel odour, not just mustiness
Cigarette smoke from a guest who smoked in a non-smoking room, food ordered to the room, pets in pet-friendly rooms, and cosmetics are all handled by the same principle.
7. It can be run as a standing cycle rather than a fix after the fact
Large chains use it on a standing cycle — rooms vacant more than three days, rooms reported for smell, and every floor quarterly — which prevents the problem rather than chasing it.
8. Your own housekeeping team can run it
With the hotel's own machine, the housekeeping team already servicing the room simply adds the treatment step — far cheaper than per-visit contracting for a hotel with dozens of rooms.
9. Internationally recognised certification you can cite to guests and OTAs
The Master Ozone Generator is tested by the Department of Medical Sciences and by Intertek in the UK — something a hotel can state on its platform profile and cite credibly when replying to reviews.
10. The cost per room is less than one night's room rate
Against 1,400,000 baht of lost bookings over two months, the cost per room is a small fraction. And on bookings of 15,000 baht or more you also receive a free CHEMGENE HLD4H disinfection spray service.
Before and after
Before
- Housekeeping following every standard step, with supervisor inspection before every sale
- Added curtain washing, monthly mattress protector washing, more frequent air conditioning servicing and air purifiers
- 17 reviews about musty smell in one high season, 15 of them in the older wing
- Overall score down from 8.7 to 7.1, pushing the hotel lower in booking platform rankings
- Bookings down about 22% over the following two months — roughly 1,400,000 baht
- Discounting older-wing rooms attracted guests who wrote more negative reviews, worsening the problem
After
- All 28 older-wing rooms ozone-treated, about 30 minutes each
- Done in the vacant window between checkout and check-in, with no rooms taken out of sale
- Ozone reaching the air conditioning box, mattress foam and carpet underlay together
- No further reviews about smell through the following high season
- Overall score back to 8.5 within four months and rankings restored
- A standing cycle set: rooms vacant over 3 days, rooms reported for smell, and every floor quarterly
How we get you started, in 3 steps
1. Survey and assess the rooms and building
We look at the number and size of rooms, the bedding and carpet materials, the air conditioning system, the age of the building, and any history of damp or leaks — to set the correct exposure time per room type and sequence the work so it does not affect room sales.
2. Treat during the vacant window between guests
The room is sealed, the air conditioning is set to recirculate so ozone reaches the whole system, and the treatment runs on the timer for around 30 minutes with nobody in the room.
3. Ventilate and set a standing cycle
Doors and windows are opened until the ozone smell has gone and the room returns to sale as normal. We then help you set a standing cycle — rooms vacant over three days, rooms reported for smell by guests, and every floor quarterly — so the problem is prevented rather than chased.
What a customer says
“I added a great deal of work for my housekeeping team — more curtain washing, monthly mattress protector washing, quarterly air conditioning servicing, air purifiers. They genuinely worked harder and the reviews about smell kept coming. It was only when I spoke to a big chain that I learned they had been ozone-treating rooms on a standing cycle for years, because the smell is in the air conditioning box and the mattress, not on the surfaces housekeeping can wipe.”
Weeraya — General manager, 60-room hotel
Why reviews about smell carry more weight than any other review
When people read hotel reviews they are looking for warning signs rather than praise, and among all warning signs, words about cleanliness carry the most weight.
The reason is that readers treat other complaints as matters of taste or personal expectation. A small room for one person is fine for another; a poor view is acceptable at a low price. A musty smell is not a matter of taste.
Smell is also read as a signal about things you cannot see. A reader will immediately wonder: if the room smells like that, what is the mattress like, what are the towels like, and is the bathroom really clean?
That is why one review about smell does more damage than three about slow service — and why a hotel should address this before anything else.
Why rooms that sit vacant smell worse than rooms sold every day
Many hoteliers notice that rooms sitting vacant smell worse than rooms with guests coming and going daily, which sounds counter-intuitive.
The reason is that an occupied room has doors and windows opened, the air conditioning switched on, and natural air movement every day, while a vacant room stays sealed with the air conditioning off, leaving the air completely still for days.
In Thailand's hot, humid climate, a sealed room with no air conditioning steadily rises in relative humidity — precisely the condition that mould in the mattress, the carpet and the air conditioning box needs.
This is why large chains set their ozone cycle primarily by the number of days a room has been vacant — something a small hotel can adopt immediately without any complex system.
Frequently asked questions
How long does an ozone treatment take per room?
About 30 minutes per room on the timer, then ventilation until the ozone smell has gone, after which the room returns to sale — which fits the vacant window between checkout and check-in.
Do we have to take the room out of sale for a whole day?
No. The treatment fits into the normal vacant window between guests, so most hotels run it with no effect on occupancy at all. We help sequence the work around your room schedule.
Will mattresses, curtains and carpets be damaged?
No, when concentration and exposure time are controlled for the materials in the room, which we assess at survey. And unlike steam treatment, ozone adds no moisture to those materials.
Should the air conditioning be running during treatment?
It should, set to recirculate, because the air conditioning box is the main source of guest room odour. Running it carries ozone to the coil and ducts, which ordinary servicing cannot reach.
Can our own housekeeping team run it?
Yes, if the hotel has its own machine — which is far more economical for a hotel with dozens of rooms. We train the housekeeping team at handover in an afternoon and set the cycle with you.
How often should rooms be treated?
The pattern hotels use is: rooms vacant more than three days treated before sale, rooms reported for smell treated immediately, and every floor treated quarterly. Consistency matters more than intensity.
Does it work on cigarette smoke in a non-smoking room?
Yes, and it is one of the most frequent hotel uses. A guest who smokes in a non-smoking room can make it unsellable for days; ozone treatment returns it to sale the same day or the next.
Is there certification we can cite to guests?
Yes. The Master Ozone Generator is tested by the Department of Medical Sciences, Ministry of Public Health, and by Intertek in the UK. We provide the documentation for you to use when replying to reviews and on your listing profile.
One review about smell costs more than treating a whole floor
Weeraya's hotel lost about 1,400,000 baht of bookings over two months and 1.6 points of score that affected rankings for months afterwards — from a problem housekeeping could not fix because it was not on the surfaces.
Ozone treatment takes about thirty minutes per room, runs in the vacant window between guests, reaches the air conditioning box, the mattress and the carpet underlay together, and leaves no residue.
If you manage a hotel, a resort, a serviced apartment or any accommodation with a guest room odour problem, send us your room count and building details and we will assess it and set a treatment cycle around your room schedule.
See the ozone disinfection and odour removal service — click here
See product and price — click here
Call 065-556-6294 or add LINE @whd268
#OzoneDisinfectionService#HotelOzoneTreatment#MustyRoomOdour#MouldInAirConditioning#MasterOzoneGenerator#WorldHealthDisinfection#HotelHygiene2026
