Many urban and larger temples have fitted air conditioning to their assembly halls over the past decade, for an entirely good reason: so elderly attendees can sit through a ceremony without becoming dangerously overheated.

The side effect nobody discusses is that a hall which used to be an open pavilion with air flowing through it constantly has become a sealed room, with doors and windows shut so the cooling can cope — and at a ceremony with eight hundred people, it is the densest enclosed space in the community.

What follows is the whole story: the day of the ceremony, the three weeks of suspended activities, 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 story

An annual ceremony: 800 people in an air-conditioned hall

A temple on the outskirts of a city has fourteen resident monks, twenty-two committee members and staff, and a six-hundred-square-metre assembly hall that was fitted with air conditioning five years ago.

That year's annual merit ceremony drew about eight hundred attendees, mostly elderly people from the surrounding community and from other districts who travelled in groups by bus.

The ceremony ran from seven in the morning until one in the afternoon. For all four hours everyone was inside the hall with doors and windows shut so the cooling could cope, with several rounds of collective chanting, a sermon, and the offering of the midday meal.

Midday was when everyone removed their masks together, because that is when the temple's meal is served — and at a merit ceremony, eating together is part of the occasion, not something that can be cut.

Ten days: 7 monks and 12 committee members

Six days after the ceremony monks began falling ill. Two on the first day, and seven of fourteen within ten days.

Twelve of the twenty-two committee members and staff also fell ill — the people who had helped run the event and had been in the hall for the full four hours alongside the attendees.

There were also reports from the visiting groups that several of their members had fallen ill after returning home, which the temple had no way to trace, because merit ceremonies have no attendee registration.

With seven of fourteen monks ill, the temple had to suspend all activities for three weeks: the morning and evening services attended by lay people, funeral chanting, and all invitations to officiate outside the temple.

Things that genuinely cannot be suspended, but were

Suspending temple activities for three weeks affected the community in ways that never show as money. Five funerals in that period had to invite monks from a more distant temple, adding travel costs for bereaved families.

Elderly people in the community who attend morning services daily — an act of faith and also their social routine — had to stay home for three weeks, which for many meant losing the only social activity in their week.

Financially, temple donations dropped noticeably in that period, affecting utility bills, food and planned repairs — around 280,000 baht in total.

And what worried the committee most was whether people would dare to come in the same numbers to the next ceremony, because the story was known throughout the community within days.

The advice from the sub-district health promoting hospital

An officer from the sub-district health promoting hospital visited and made one observation the committee had never considered.

She pointed out that ten years ago this temple's assembly hall was an open pavilion with air flowing through it constantly, and merit ceremonies with eight hundred people had never caused a problem like this. What had changed was the air conditioning and the closed doors and windows.

She did not suggest removing the air conditioning — many elderly people come to the temple more often precisely because it is cool. She suggested that once an open building becomes a sealed one, air management has to be added to replace the natural airflow that has been removed.

What the temple needed was a machine that could fog a six-hundred-square-metre hall before and after ceremonies, at a price the temple's fund or a donation drive could cover, and that monks or committee members could operate themselves.

What it actually costs

Why the usual fixes fail

10 reasons the AIROFOG U260 solves it

1. 15-30 micron droplets cover a 600 sqm assembly hall

An assembly hall has wooden flooring, seating mats, pillars and a high ceiling — far more surface than sweeping can reach. Droplets in this range fill the hall's volume and settle across every surface in one pass.

2. It runs before and after a ceremony without affecting the rites

The hall is already empty before seven in the morning and after one in the afternoon. Fogging uses a small part of those windows, so nothing in the order of service changes and no timing shifts.

3. You do not have to limit the number of attendees

This is the most important point for a temple, because turning away someone who has come to make merit is neither practical nor right. Air management lets the temple receive the same numbers as before.

4. An 800-watt motor suits a large hall with a high ceiling

Assembly halls typically have ceilings five to eight metres high. An under-powered fogger cannot reach them. The U260's motor carries the mist far enough for a building this size.

5. It covers the hall, the monks' quarters, the kitchen and the bathrooms

One machine serves the whole temple: the assembly hall on ceremony days, the monks' shared quarters, the kitchen where offerings are prepared, and the bathrooms attendees use — the four places that belong in the fogging round.

6. The adjustable nozzle is safe around images and valuables in the hall

The hall holds Buddha images, offerings, robes and sound equipment. A drier nozzle setting and the clearances we define let you fog without affecting any of them.

7. Floors dry fast and are not slippery, which matters for elderly attendees

Most attendees are elderly and many walk barefoot in the hall. Cold fogging at this droplet size leaves a thin, fast-drying film, not a puddle.

8. Monks or committee members can run it, with nobody to hire

No contractor for every ceremony. A committee member or temple staff member fills and fogs themselves, learning it in an afternoon — which matters greatly for a temple on a limited budget.

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 temple that needs to reassure its community, that provenance is a clear answer.

10. It gives people the confidence to return to ceremonies

A temple that fogs the hall before every ceremony can post a notice and announce it at community meetings — which is what makes elderly attendees and the relatives who bring them comfortable enough to return in the same numbers.

Before and after

How we get you started, in 3 steps

What a customer says

What changed when an open pavilion became a sealed hall

A traditional Thai assembly hall is an open pavilion: raised floor, ventilation openings on every side, and deep eaves that keep out sun and rain without needing walls. That architecture keeps air flowing constantly with no machinery at all.

Over the past ten to fifteen years many temples have fitted air conditioning to these halls, with entirely good intentions: elderly attendees, who make up the core of a temple's community, cannot sit through four hours in a hot hall, and many now come far more often because it is cool.

But installing air conditioning forces you to close the walls, the ventilation openings and the doors and windows so the cooling can cope — which unintentionally cancels the natural ventilation the original architecture already provided.

This is why a temple that has renovated its hall should add air management as well. Not because air conditioning is bad, but because when you remove the natural airflow, something has to take its place.

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, leaving seating mats damp and wooden floors slippery.

The 15-30 micron band is the working range. Droplets stay airborne long enough to fill a six-hundred-square-metre hall's volume and reach the high ceiling, then settle as a thin, even, fast-drying film. The wooden floor is not slippery for elderly people walking barefoot.

It is also why an adjustable nozzle matters more than tank size. The zone around images and sound equipment needs a drier setting, while the tiled kitchen and bathrooms take a normal one.

For a temple the practical test is simple: after a pass the wooden floor should be walkable within minutes and not slippery, the seating mats should not feel damp, and the high ceiling corners should genuinely have been treated.

Frequently asked questions

#COVID19DisinfectionSprayer#AirofogU260#ULVFoggingMachine#TempleDisinfection#CommunityHallHygiene#WorldHealthDisinfection#PlaceOfWorship2026