Cram School Before Exams: A 60-Seat Windowless Classroom, 27 Students Ill, and 41 Seats Refunded
Last updated: 6 Sep 2026 | 23 Views |
COVID-19 disinfection sprayer 2026 for cram schools and tutoring centres
Cram School Before Exams: A 60-Seat Windowless Classroom, 27 Students Ill, and 41 Seats Refunded
Why the classroom with the fastest turnover is the riskiest one, and what 15-30 micron fogging changes about the fifteen minutes between sessions.
A cram school classroom is a room where sixty students sit shoulder to shoulder for three and a half hours with no windows at all, and fifteen minutes later another sixty walk in and take the same seats. Four times a day, seven days a week in exam season. This is what happened at one school in Siam, Bangkok.
A cram school differs from an ordinary school in one decisive way. A school has the same students in the same room all day. A cram school replaces the entire room every three and a half hours, four times a day, which means one room takes two hundred and forty people through it daily.
Most operators keep the place properly clean: desks wiped, floors mopped, bins emptied, sanitiser at the door. All correct, and all of it surface work — while the air in a sixty-seat room with no windows, running on recirculated air for fourteen hours a day, is never addressed at all.
What follows is the whole story: the exam-season weeks, the forty-one refunded seats, and the change that stopped it. At the centre of it is the AIROFOG U260 ULV cold fogger, a German-engineered machine producing 15-30 micron droplets.
The weeks every session was full
Siriporn has run a cram school in Siam for eight years. Three classrooms: sixty seats, thirty-five seats, and twenty seats. All three are in a converted commercial building with not one window that opens.
In the six weeks before university entrance exams the timetable is the fullest of the year. The large room runs four sessions a day, three and a half hours each, with fifteen minutes between sessions for one group to leave and the next to arrive.
Those fifteen minutes are when housekeeping goes in for a quick desk wipe and a bin empty, then leaves. The door stays open for about five minutes. For the remaining ten, the next sixty students are already filing in and claiming seats.
The students in that room did what students always do before exams: quizzed each other about the paper, worked through problems together, ate snacks brought from home — and many had their masks off, because after three and a half hours in that room it becomes uncomfortable.
Twelve days, 27 students ill
It started with a girl in the afternoon session who had been coughing for two days but came anyway, afraid of falling behind. The following week seven students called in sick. The week after that nineteen. Twenty-seven within twelve days.
When Siriporn cross-checked the names against the timetable, the ill students were spread across three different sessions in the large room. It was not one class. It was that room.
Two of the tutors who taught in the large room fell ill too, which was worse, because each tutor teaches a specific subject and cannot be substituted. Every one of their classes had to move — eleven in total.
And moving classes during the six weeks before exams is not ordinary rescheduling. Students have no spare time, their timetables are already full, and the exam date does not move with them.
Forty-one seats refunded
Parents started calling once word spread that several students were ill. Every one of them asked the same question: is the classroom disinfected between sessions?
All Siriporn could say was that housekeeping wiped the desks each session and there was sanitiser at the door. It was true, and it was not an answer any parent worried about their child missing an exam was willing to accept.
Forty-one parents asked for a refund on the remainder of the course. The school refunded all of them in full to preserve the relationship — roughly 490,000 baht.
The more expensive part was the next intake. A cram school fills almost entirely on recommendations from older students and parent group chats. Bookings for the following summer course fell by about thirty per cent, a number that affected the whole year.
The fifteen minutes that had only ever been a desk wipe
Siriporn visited a language school she knew and saw a staff member walking through a classroom spraying something between sessions. She asked, and got an answer that matched her problem exactly.
That school fogged its classrooms at every changeover with a ULV machine. It took a few minutes inside the fifteen the room was already empty — no extending the break, no reducing the number of sessions.
That was what Siriporn had been missing. The fifteen minutes between sessions was not just a desk-wiping window. It was the only period the room was empty, and the only chance to treat the whole room's air before another sixty students walked in.
What the school needed was a machine that could treat a sixty-seat room in minutes, that would not leave desks wet enough to smudge worksheets, that was safe around the projector and sound system, and that would reach the ceiling and the air vents nobody had touched in eight years.
The real impact, point by point
Students take more risk in the run-up to exams
A student sitting university entrance exams will come to class unwell, afraid of falling behind and afraid of wasting course fees already paid. That is not carelessness; it is a calculation they genuinely have to make.
One tutor absent means several classes gone
Each tutor teaches a specific subject in a style students paid for specifically. There is no substitute. In this case two tutors ill meant eleven classes had to move.
There is nowhere to move a class to before exams
The six weeks before exams are the fullest in everyone's timetable, and the exam date does not shift. Moving a class becomes cutting content, not just changing a time.
Parents decide fast when their child's exam is involved
A parent who has invested tens of thousands of baht in a once-in-a-lifetime exam does not wait to see how things develop. Requesting a refund and moving to another school happens within days.
Why the usual approach is not enough
Wiping the desks between sessions
Wiping desks is necessary and does address what hands touch. It does nothing about the air in a room where sixty students just spent three and a half hours, and it never reaches the ceiling or the air vents.
Sanitiser at the classroom door
Sanitiser helps with contact transmission and reassures parents who see it. It has no relationship at all to what students breathe for three and a half hours in a windowless room.
Opening the door to ventilate between sessions
Five to ten minutes of an open door in a commercial building with no windows and no cross-draught barely changes the room's air — and the next group is already sitting down by minute five.
Reducing seats per session
Cutting from sixty seats to forty helps with distance, but in a sealed room on recirculated air fine aerosol still travels throughout. It also forces you to add sessions, which means the room is occupied for longer each day.
Deep cleaning between courses
A deep clean makes the room spotless the day it happens, and the first week of the new course puts it straight back. More importantly, it does not answer the parents' question about what happens between sessions.
What those fifteen minutes can actually do
The requirement is not more meticulous wiping. It is a treatment aimed at the volume of air in the whole classroom, that finishes inside the fifteen minutes between sessions, without extending the break or cutting sessions.
That is exactly what ULV cold fogging is designed for. ULV, ultra-low volume, means the machine breaks disinfectant into droplets fine enough that the output behaves more like fog than spray. The mist stays airborne long enough to fill the room, then settles evenly on every surface, including the ceiling and the air vents.
The machine Siriporn's school chose is the AIROFOG U260: a German-engineered ULV cold fogger with an 800-watt motor and an adjustable nozzle producing 15-30 micron droplets, running on water plus the disinfectant you choose.
10 reasons to choose the AIROFOG U260 from World Health Disinfection
1. 15-30 micron droplets treat a 60-seat room in full
A sixty-seat classroom has desks, chairs, walls, a ceiling and air vents that desk-wiping never reaches. Droplets in this range fill the room's volume and settle across every surface in a single pass.
2. It finishes inside the fifteen-minute changeover
This is the single most important constraint in the cram school business, and it is exactly what ULV fogging fits. A few minutes to fog, a short closed-door pause, then the next group enters — with no reduction in sessions per day.
3. You do not have to reduce seat numbers
The alternative is fewer seats, which cuts revenue per session immediately. Fogging between sessions lets you keep the same seat count, which is the basic economics of this business.
4. An 800-watt motor covers every room in the school
One machine serves the sixty-seat room, the thirty-five, the twenty, plus the bathrooms and the waiting area. You do not need a unit per room.
5. The adjustable nozzle is safe around projectors and worksheets
A cram school classroom has a projector, a sound system, microphones and worksheets left on desks. A drier nozzle setting lets you fog it without damaging any of that.
6. It runs on water and the disinfectant you choose
The U260 is a delivery system, not a chemical lock-in. You can pick a low-odour product suited to a room children study in immediately afterwards, and we work out the correct dilution.
7. Desks dry before the next group sits down
Cold fogging at this droplet size leaves a very thin, fast-drying film. Desks do not end up wet enough to smudge worksheets, and the room is ready on the original schedule.
8. Your own housekeeping staff can run it
No contractor needed. The person already going in to wipe the desks between sessions simply adds the fogging step. They learn it in an afternoon.
9. It is the same class of equipment hospitals use
The U260 was designed for COVID-19 disinfection and is used in hospital and laboratory settings. For a school answering parents, that provenance ends the conversation.
10. It answers the question parents are actually asking
The question is whether the classroom is disinfected between sessions. A school that fogs every changeover can say yes, post the schedule at the door, and show a short video — which becomes a reason parents choose you.
Before and after
Before
- Cleaning limited to desks, floors and bins between sessions
- The classroom ceiling and air vents never disinfected in eight years
- The large room taking 240 students a day with no air management at all
- 27 students and 2 tutors ill within 12 days
- 11 classes moved during the 6 weeks before exams, when nothing can move
- 41 parents refunded, roughly 490,000 baht, and next course bookings down 30%
After
- ULV fogging of every classroom at every changeover, inside the existing 15-minute break
- Coverage of the ceiling, air vents, walls and under every desk row
- No reduction in seats per session, so revenue per session is unchanged
- No further classroom illness cluster across the following two courses
- The fogging schedule posted at the classroom door with a video for parents
- Next course bookings back to previous levels, with new parents citing this as their reason
Three-step use
1. Look at the actual room, not just the seat count
Room size and ceiling height, how many air conditioning units and where, how much electrical equipment and paperwork sits in the room, how many sessions a day, and how many minutes the break really is. Those five things decide the nozzle setting and the timing. Send us the room layout and we will tell you.
2. Install the machine and train housekeeping and the front desk
We deliver the U260 with the nozzle set dry enough for a room with a projector and worksheets, the correct dilution for the product you choose, and a route that finishes inside your actual break time. Training takes an afternoon.
3. Fit it into the changeover routine you already run
The routine that works is boring and repeatable: fog at every changeover, and fog every room before opening and after closing. Once it sits inside the existing desk-wipe step, it becomes simply what the school does — and something you can tell parents.
When parents called and asked whether we disinfect the classroom between sessions, all I could say was that housekeeping wipes the desks. True, but not enough for a parent afraid their child will miss an exam. Now we fog every changeover inside the same fifteen minutes, we did not have to remove a single seat, and the schedule is posted at the door. Two courses since, and no cluster at all.
Siriporn - Director, cram school, Siam, Bangkok
Why a cram school is a different problem from an ordinary school
An ordinary school keeps the same students in the same room all day. If one falls ill, the circle of contacts is that one classroom, and the teacher knows who sat where.
A cram school replaces the whole room every three and a half hours. A sixty-seat room running four sessions takes two hundred and forty people a day, and each session's students come from different schools, different districts, sometimes different provinces.
That means a single cram school classroom connects people from dozens of schools every day — a role nobody designed for it and almost nobody thinks about.
And because those students are not in one shared system, contact tracing afterwards is essentially impossible. The only thing the school genuinely controls is the state of the room before the next group walks in.
What 15 to 30 microns actually means in practice
Droplet size is the specification that decides whether a machine solves this problem or merely makes things wet. Below roughly 10 microns, droplets are so light they can drift away before doing useful work. Above about 50 microns they behave like spray: they fall fast, and they wet the worksheets left on desks.
The 15-30 micron band is the working range. Droplets stay airborne long enough to fill a sixty-seat room's volume and reach the ceiling and air vents, then settle as a thin, even, fast-drying film. The room is ready for the next session inside the existing break.
It is also why an adjustable nozzle matters more than tank size. A room with a projector and sound system needs a drier setting than a bare tiled waiting area. Adjusting the nozzle gets you both from one machine.
For a cram school the practical test is simple: after a pass, the desks should be dry enough to put worksheets on immediately, the projector lens should not be fogged, and the ceiling corner above the back row should genuinely have been treated.
Frequently asked questions
Can it really be done inside a 15-minute break?
Yes, and that is exactly where ULV fogging suits this business best. A sixty-seat room takes a few minutes to fog plus a short closed-door pause, finishing inside the existing break with no reduction in sessions.
Will the desks be wet enough to smudge worksheets?
No. ULV cold fogging at 15-30 microns leaves a very thin film that dries by itself within minutes. We set the nozzle dry enough for rooms with paperwork at installation.
Will the projector and sound system be damaged?
No, with the nozzle set correctly and equipment switched off during the pass. We build that into a checklist at installation.
Do we have to reduce seats per session?
No, and that is the main advantage of this approach. Fogging between sessions lets you keep the same seat count, unlike distancing, which cuts revenue per session immediately.
Can our own housekeeping staff run it?
Yes. The person already wiping desks between sessions simply adds the fogging step. We train them at handover — it takes an afternoon.
Will the disinfectant smell bother students?
That depends on the product chosen. We recommend low-odour or odourless solutions for classrooms, and opening the door for the last part of the break is enough for a typical room.
How often should a cram school fog?
At every changeover, plus every room before opening and after closing. During the six weeks before exams when every session is full, consistency matters most of all.
What does each pass cost?
The consumables are water and disinfectant, and ULV atomisation uses very little solution per pass. The cost per changeover is far below one student's course fee.
The fifteen minutes between sessions is the only thing you actually control
Siriporn's school refunded around 490,000 baht, moved eleven classes during weeks when nothing can move, and lost thirty per cent of the next intake's bookings.
Fogging at every changeover costs less than a single student's course fee and runs inside the fifteen minutes you already have. It covers the whole room, does not force you to cut seats, and answers the question parents are actually asking.
If you run a cram school, a language school, a training centre or any classroom with fast turnover, send us the room layout and we will tell you exactly what it needs.
See the AIROFOG U260 and pricing
See the AIROFOG U260 ULV cold fogger, specifications, droplet range and price
Tel 065-556-6294 or LINE @whd268
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