Eight Rescue Ambulances, Eleven Volunteers Ill in Two Months, and Two Vehicles Taken Off the Road
Last updated: 7 Sep 2026 | 4 Views |
The people who go out to help everyone else are the ones most exposed
Eight Rescue Ambulances, Eleven Volunteers Ill in Two Months, and Two Vehicles Taken Off the Road
Why wiping the stretcher and fogging after a case is not enough, and why ozone suits rescue vehicles particularly well
An ambulance is a sealed space of about six cubic metres that carries several infectious patients a day — and the same volunteers sit in it for an entire shift. Almost nobody talks about that risk.
Khun Thira is 44 and heads operations for a rescue foundation in Samut Prakan: eight ambulances, 62 rotating volunteers, and an average of 34 calls a day.
Calls range from road accidents and home emergencies to elderly transfers and patients with respiratory symptoms whose infection status is unknown at the moment of pickup.
Between June and July 2025, 11 of the 62 volunteers developed respiratory infection within a short period. Three were hospitalised, and the foundation had to take two ambulances off the road for lack of crew.
The story
Eleven people in two months is not coincidence
Khun Thira says volunteers falling ill is always part of rescue work — everyone has direct patient contact in uncontrolled conditions. But eleven in two months was several times higher than anything he had seen.
He built a table of which vehicles each volunteer had crewed in the two weeks before their symptoms, and found that nine of the eleven had crewed the same two vehicles: unit 3 and unit 6.
Looking at what made those two different, the answer was straightforward. They handled the most calls, because they were stationed at the busiest post, and they were the two oldest vehicles in the fleet — 11 and 13 years old.
When he saw those numbers, he says, he knew immediately that the problem was not volunteer discipline. The same volunteers also crewed other vehicles, and those who crewed only other vehicles did not get sick.
Why an ambulance is the most concentrated sealed space of all
The infection control consultant the foundation brought in explained that an ambulance patient compartment holds roughly 6 to 8 cubic metres of air — smaller than the bathroom in many houses.
In that space there are three or four people: the patient, two or three crew, and sometimes a relative — with the doors sealed and air conditioning that mainly recirculates internal air.
When a patient with respiratory symptoms coughs or sneezes less than a metre away, droplets fill that entire volume within seconds, and some are drawn into the air conditioning and circulated back out again.
What makes older vehicles worse, the consultant added, is air conditioning that has run for more than a decade with the ducting never stripped and cleaned, and seats and wall linings with cracks and seams where organisms accumulate — none of which surface wiping can reach.
What the foundation already did, and why it was not enough
The foundation has a fairly rigorous post-case procedure. Crews wipe the stretcher, grab rails and contact surfaces with disinfectant, change the stretcher linen every time, and dispose of infectious waste properly.
For suspected infectious cases there is an additional step: fog the patient compartment with disinfectant and open the doors to ventilate for fifteen minutes before the next call.
The problem is that on busy days the gap between calls is sometimes five minutes, and the vehicle must leave the moment a call comes in. The designed procedure gets compressed with nobody intending it.
More importantly, even when every step is completed, wiping surfaces and fogging do not address organisms inside the air conditioning ducting, in the seams of the wall lining, or in the seat foam — where accumulation has been building for years.
What changed after trying it on two vehicles
Khun Thira started with units 3 and 6, the two vehicles linked to most of the sick volunteers. The team worked at the foundation's depot overnight, while reserve vehicles covered.
They had every equipment locker opened and the under-seat storage hatches lifted, and set the air conditioning to recirculate so the gas travelled through the ducting. About thirty minutes per vehicle following the machine's cycle.
The first thing the volunteers noticed the next day was not about infection. It was the smell. They said the characteristic ambulance smell that everyone was so used to they had stopped noticing it had gone from the whole vehicle.
The foundation then set a weekly schedule for every vehicle, plus immediate treatment after any high-risk case. Over the following six months, only 2 of 62 volunteers developed respiratory infection.
What it actually costs
Sick volunteers mean vehicles come off the road
An ambulance needs two or three crew per shift. With eleven people ill at once, the foundation had to stop running two vehicles — which means longer response times for emergency patients in that area.
Six cubic metres is the highest concentration there is
An ambulance patient compartment holds less air than many household bathrooms, with three or four people sealed inside. When a patient coughs less than a metre away, droplets fill that volume in seconds.
The gap between calls is shorter than the procedure needs
On busy days there can be five minutes between calls, and the vehicle must leave the moment a call comes in. A well-designed disinfection procedure gets compressed with nobody intending it.
The next patient carries a risk nobody discusses
Besides the crew, the next patient into that vehicle breathes the same air — and many of them are elderly or already immunocompromised, the most vulnerable group there is.
Why the usual fixes fail
Wiping the stretcher and contact surfaces after every case
Necessary and it must continue. But it addresses contact transmission on surfaces a cloth can reach, not droplets suspended in the air or already drawn into the air conditioning.
Fogging the patient compartment with disinfectant
It helps at surface level and partially in the air, but the aerosol does not travel into the air conditioning ducting or the seams of the wall lining — and it leaves vapour in a sealed space that the crew and the next patient must breathe.
Opening the doors to ventilate between calls
It genuinely dilutes airborne droplets and should be done, but it needs time, which rescue work does not have — and it does not remove organisms on surfaces, in the seats or in the air conditioning.
Scheduled vehicle air conditioning servicing
Necessary, but it cleans only the removable parts. In a vehicle over a decade old whose ducting has never been stripped, the organic accumulation in there is precisely what scheduled servicing never touches.
Requiring full PPE on every case
The correct standard and highly effective during a case. But volunteers do not wear masks for the whole shift — particularly while waiting for calls in the vehicle or cleaning it — which is time spent in the same body of air.
Rescue work needs something that treats the whole vehicle's air and finishes fast enough to get back on the road
An ambulance poses two requirements that constantly conflict. It must genuinely disinfect a sealed space that carries several infectious patients a day, and it must be ready to respond at any moment.
Every conventional method fails one or the other. Wiping and fogging are fast but do not cover the ducting or the seat foam. Air conditioning servicing covers more but requires a technician booking and takes the vehicle out of service for a day.
Ozone satisfies both, because it is a gas that fills the whole air volume of the patient compartment and the cab. With the vehicle sealed and the air conditioning recirculating, ozone is drawn into the coil and ducting while penetrating the seat foam, the seams of the wall lining, the equipment lockers and the under-seat storage. Where it meets viruses, bacteria or mould, the third oxygen atom breaks away and destroys the envelope or cell wall. Then the ozone decomposes back into ordinary oxygen, leaving no chemical residue in a sealed space that the crew and the next patient must breathe — and the cycle takes about thirty minutes.
10 reasons ozone treatment solves it
1. It treats the whole vehicle's air, not just wipeable surfaces
In six cubic metres, droplets from a cough fill the space within seconds. Surface wiping handles only part of it. Ozone, as a gas, treats the whole compartment's air at once.
2. It reaches vehicle air conditioning ducting that has never been stripped
A decade-old ambulance has ducting that has never been cleaned in its service life. With the air conditioning recirculating during the cycle, ozone travels through the whole system that scheduled servicing cannot reach.
3. It penetrates seat foam and wall lining seams
Ambulance seats and linings have cracks, seams and foam where organisms accumulate for years, beyond the reach of wiping or fogging. A gas gets there without wetting anything.
4. No chemical residue in a sealed space people must breathe
Ozone decomposes back into ordinary oxygen, so there is no lingering vapour in the patient compartment and no deposit on the stretcher or grab rails — unlike fogging, which leaves vapour for the crew and next patient.
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 a patient-carrying space should hold.
6. It reaches equipment lockers and under-seat storage
Rescue equipment is kept in closed lockers and compartments whose interiors are almost never disinfected. Ozone enters every compartment left open in one cycle, with no need to remove and wipe each item.
7. It handles the characteristic ambulance odour too
Ambulances accumulate odour from blood, secretions, disinfectant and moisture in the seats — which crews stop noticing and patients and relatives register immediately. One cycle addresses both organisms and smell.
8. About thirty minutes per vehicle, done at the depot
The automatic digital timer cycle runs roughly thirty minutes — two to start, twelve to disperse, twelve to purify, twelve to rest. It fits a depot slot covered by a reserve vehicle, with no impact on service.
9. It adds no moisture to seats and linings
Hosing and steam add water to the very foam that is the problem, feeding organisms directly. Ozone is a dry gas and leaves nothing behind for the next cycle.
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
Before
- 11 of 62 volunteers developing respiratory infection in two months
- Three volunteers hospitalised
- Two ambulances taken off the road for lack of crew
- 9 of the 11 sick volunteers having crewed the same two vehicles — the oldest and busiest in the fleet
- Gaps between calls as short as five minutes, compressing the disinfection procedure
- Air conditioning ducting on 11- and 13-year-old vehicles never once stripped and cleaned
After
- Only 2 of 62 volunteers developing respiratory infection across the following six months
- Years of characteristic ambulance odour gone from the whole vehicle
- All eight ambulances back on the road to full schedule
- About thirty minutes per vehicle at the depot, covered by a reserve unit
- No need to remove and wipe rescue equipment item by item
- Weekly treatment for every vehicle, plus immediate treatment after any high-risk case
How we get you started, in 3 steps
Survey and assessment
The team assesses the air volume of the patient compartment and cab, the vent positions and duct runs, the condition of seats and wall linings, and the equipment locker positions, then sets the cycle for each vehicle.
Preparation and sealing
Stained surfaces are wiped and infectious waste disposed of first. Every equipment locker and under-seat storage hatch is opened so the gas can reach inside. Doors and windows are sealed, the air conditioning is set to recirculate, and everyone leaves the vehicle.
Ozone cycle, ventilation and check
The machine runs its automatic cycle of about thirty minutes. The doors are then opened for full ventilation, surface moisture in the seats is checked, and the vehicle returns to the duty roster.
What a customer says
“I have worked in rescue for twenty years and I know volunteers get sick. But eleven in two months is not normal. When I built the table and saw that nine of the eleven had crewed the same two vehicles, I knew the problem was the vehicle, not the people. Since we treated the whole fleet and put it on a schedule, only two people have been ill in six months — and the smell we had all lived with for a decade is gone too.”
Khun Thira S. — head of operations, rescue foundation, Samut Prakan
Why an ambulance carries more risk than an emergency department
A hospital emergency department has a large air volume, purpose-designed ventilation, many air changes per hour, and isolation rooms for suspected infectious patients.
An ambulance has none of those. Six to eight cubic metres of air, no true air-change ventilation, air conditioning that mainly recirculates, and no way to isolate anyone because there is only one space.
Critically, an ambulance takes patients before anyone knows what they have, because diagnosis happens at the receiving hospital, not in the vehicle. Crews therefore work with patients of unknown infection status on every single case.
Combine that with the requirement to leave the moment a call comes in, leaving very little time for disinfection between cases, and an ambulance becomes the highest-risk point in the emergency medical system — and the one that gets the least attention for infection control.
Which other vehicles face the same conditions
Hospital patient transport and elderly care centre shuttles meet nearly every one of the same conditions: a small sealed space, vulnerable passengers, and recirculating air conditioning.
Rescue and fire vehicles have a slightly different profile — organisms from casualties plus soot and chemicals carried back from the scene, accumulating in the seats and the air conditioning in exactly the same way.
Mortuary transport vehicles and the foundations that operate them are another group where both microbial and odour control matter enormously, for hygiene and for the feelings of bereaved families alike.
For all of them the same principle holds: if the organisms and odour are in the air conditioning and the seat foam, surface wiping will never be enough, and a gas is the only method that reaches all of it in one cycle.
Frequently asked questions
How long does one vehicle take?
About thirty minutes following the machine's cycle, plus ventilation. It is done at the depot while a reserve vehicle covers, and the ambulance returns to the roster immediately after.
Does rescue equipment have to be taken out?
No. We only recommend opening every equipment locker and under-seat storage hatch so the gas reaches inside — which is an advantage, because there is no need to wipe each item individually.
Is there residue in the patient compartment?
No. Ozone decomposes back into ordinary oxygen after reacting, so no vapour lingers and no deposit remains on the stretcher, grab rails or seats — unlike fogging, which leaves vapour in a sealed space.
How often should it be done?
For vehicles taking calls daily, weekly as a routine, plus immediate treatment after any high-risk case such as a patient with severe respiratory symptoms.
Does it replace wiping and fogging after a case?
No — they complement each other. Post-case wiping is essential for visible contamination; ozone treats the whole vehicle's air and the places wiping cannot reach. Both should be done in their own roles.
Does it damage seats or vehicle electronics?
No. Concentration and duration are controlled by the certified machine's digital timer, and the team assesses any sensitive equipment at the survey stage.
What certifications does the equipment hold?
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.
Is anything included for fleets?
For bookings of 15,000 baht and above, WHD includes free hospital-grade CHEMGENE HLD4H spray disinfection, certified by Mahidol University and NHS England — suited to high-contact surfaces such as stretchers, grab rails and door handles.
People who spend the day helping everyone else should go home without taking anything with them
If your volunteers or crew have an abnormally high rate of respiratory illness, build a table of which vehicles the sick people crewed. The numbers usually point at the vehicle, not at anyone's discipline.
Ozone treatment handles the whole vehicle's air at once, reaching air conditioning ducting that has never been stripped, the seat foam, the seams in the wall lining and the equipment lockers — leaving no chemical residue in a sealed space that both the crew and the next patient have to breathe.
For bookings of 15,000 baht or more, WHD includes free hospital-grade CHEMGENE HLD4H spray disinfection.
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