Does ozone treatment work on a ship - and what does it actually kill?
Ozone clears garbage-room and smoke odour aboard, but mould is harder than the marketing says. Test figures, re-entry safety and when to use something else.
Yes, for odour: a portable ozone unit run for a few hours in a closed, empty garbage room, store or cabin will clear smells that cleaning alone leaves behind. It also reduces bacteria and viruses on surfaces, though by less than most marketing implies. It is weak against mould spores - one accredited test measured about a 20% reduction - and the space must be empty until the ozone has cleared.
That answer holds for the low-output UV-C units most ships would carry, such as the JIMCO OZ Series. The rest of this guide explains the options, what the test numbers really say, and how to use ozone without damaging the space or the crew.
What are the options for resetting a smelly or contaminated space aboard?
There are four realistic approaches, and they solve different problems.
Manual cleaning with a chemical disinfectant. This is the only method that removes the source - the spilled liquid, the rotten crate, the mould growth. Nothing else replaces it. Its weakness is reach: odour held in fabric, insulation and behind fixed shelving survives a wipe-down.
A portable UV-C ozone unit. A UV-C lamp at around 185 nm splits oxygen into ozone, and a fan spreads it through the closed space. JIMCO's OZ1000, OZ1000T and OZ2000 work this way, drawing 30 or 60 W and rated by room volume: 125 m³ or 250 m³ for odour treatment. The output is modest, so cycles are measured in hours.
A corona-discharge "shock" generator. Common in the restoration trade, these use a high-voltage discharge to produce much more ozone, usually rated in milligrams per hour. More ozone means faster treatment and a longer wait before re-entry. Corona discharge in humid air can also produce nitrogen oxides, which UV-C generation avoids. Output claims vary widely between manufacturers and are hard to check.
A continuous low-ozone purifier. Units such as the JIMCO MAC500s run in occupied spaces and are designed to keep ozone below the 0.1 ppm workplace figure. They maintain a space; they do not reset one.
How do the options compare?
| Manual clean + disinfectant | UV-C ozone unit (e.g. JIMCO OZ2000) | Corona-discharge shock generator | Continuous purifier (e.g. JIMCO MAC500s) | |
|---|---|---|---|---|
| Space must be empty | No (PPE as per label) | Yes | Yes | No |
| Removes the source | Yes | No | No | No |
| Reaches fabric and hidden surfaces | Poorly | Yes | Yes | Slowly |
| Typical cycle | Labour time | 1–4 h | Shorter at high output | Continuous |
| Power | - | 30–60 W | Varies | Low |
| Consumables | Chemicals, cloths | UV-C lamp, 8,000 h | Plates or cells | UV-C lamp |
| How it is rated | Product label | Room volume | mg/h output | Room volume |
| Nitrogen oxides | - | None stated by JIMCO | Possible in humid air | None stated by JIMCO |
The strongest practical combination aboard is the first two together: clean out the source, then run an ozone cycle to clear what is left in the air and the soft surfaces.
What do concentration, time and humidity actually buy you?
Ozone's effect depends on three things multiplied together: how much ozone is in the air, for how long, and how humid it is. Published ozone-gas research is clear on this. In the widely cited work by Hudson and colleagues (2009), inactivating viruses on surfaces by at least 3 log (99.9%) took ozone at 20–25 ppm with a short burst of humidity above 90%.
A small UV-C unit does not get close to those concentrations. In JIMCO's own accredited test - Dr. Brill + Partner GmbH, report L20/1055MV.1, August 2020 - an OZ2000 ran in a 31 m³ room and peaked at 1.68 ppm, with relative humidity between 75% and 85%. It compensated with time: the treatment lasted 4 hours.
The results on surfaces, as published by JIMCO:
| Organism | Reported reduction | Roughly |
|---|---|---|
| Vaccinia virus (enveloped-virus model) | 99.8% | 2.6 log |
| Mycobacterium avium / terrae | 99.99%+ | 4+ log |
| Listeria monocytogenes | 99.6% | 2.4 log |
| Candida albicans (yeast) | 98.9% | 2 log |
| Staphylococcus aureus | 97.8% | 1.7 log |
| E. coli | 95.9% | 1.4 log |
| Aspergillus brasiliensis (mould) | 20.6% | 0.1 log |
Two things follow for anyone sizing a unit. First, the 125 m³ and 250 m³ ratings are JIMCO's recommendation for odour treatment; the disinfection test used an eighth of the OZ2000's rated volume. Second, a dry accommodation space will see less effect than the humid test room did. For hygiene treatment, size down or run longer.
The honest caveat: ozone does not fix a mould problem
The figure that matters most in that table is the last one. The standard test mould fell by about a fifth, and a tenth of a log is close to no effect at all. Mould spores are among the hardest things for low-concentration ozone to reach and damage.
Some product literature, including earlier JIMCO brochures, says the OZ units eliminate mould and fungi "up to 99.9%". We have not found a test that supports that figure, and the one accredited test we have found points the other way.
What ozone does well in a mouldy space is remove the smell. So the order aboard is: find and fix the damp, physically remove the growth, clean, and then run an ozone cycle for the odour that remains in insulation, fabric and air. Used that way it is useful. Used instead of removal, it hides the problem until it grows back.
There is a second, smaller caveat. The OZ units have no ozone sensor. The OZ1000T's timer ends ozone production; it does not tell you the room is safe again.
How long before crew can go back in?
Until the ozone has cleared, which depends on the space, its ventilation and what is in it. A simple routine that works:
- Close the space and make sure nobody, and no animals, are inside. Post a notice on the door.
- Run the cycle - one to three hours for most odour jobs, longer for hygiene treatment.
- Ventilate. A fruit importer featured in a JIMCO case study leaves its chill store at least 30 minutes after a 2–3 hour cycle, often longer.
- If you treat spaces regularly, check with a handheld ozone meter that reads down to 0.1 ppm before anyone re-enters.
The reference number is 0.1 ppm, which JIMCO cites as the Danish workplace limit. A treatment cycle runs well above it: the OZ2000 test room reached 1.68 ppm, about 17 times higher. Ozone is a respiratory irritant, and at a few ppm it causes real harm.
Ozone also ages materials. Repeated exposure hardens rubber and some plastics and can fade fabrics, and it reacts with some indoor chemicals to form by-products such as formaldehyde. Take out what does not need treating, do not run a unit continuously in a space with door gaskets or cable runs, and ventilate properly afterwards.
Is ozone useful in provision stores and cold rooms?
Yes, as a between-loads reset. Ozone reduces ethylene, the gas that speeds ripening, as well as surface bacteria and odour in an emptied store. The importer in JIMCO's case story washes fruit, loads it into a store at 2–5 °C, runs an OZ1000 for 2–3 hours with the door shut, and reports from its own records that fruit lasts up to two weeks longer. No controlled comparison is described, so treat that as an operator's experience rather than a measured result.
JIMCO notes the lamp takes longer to warm up and produce ozone in a cold room. If the store is in daily use with crew going in and out, a continuous low-ozone unit such as the MAC500s is the better fit.
Summary: which should you use?
- Occupied space, ongoing smell or hygiene: continuous purifier (MAC500s) plus normal cleaning.
- Space you can empty for a few hours, odour or surface hygiene: clean first, then a UV-C ozone unit (OZ1000T if nobody can come back to switch it off).
- Mould: fix the damp and remove the growth. Ozone is for the smell afterwards, not the cure.
Frequently asked questions
Can you run an ozone generator with people on board?
How long does an ozone treatment take on a ship?
Does ozone kill mould?
What ozone level is safe to breathe?
Does ozone damage anything?
What is the difference between the JIMCO OZ Series and the MAC500s?
Is ozone approved as a disinfectant in the EU?
Talk to us about the spaces you need to treat
SepcoTech distributes JIMCO's OZ Series and MAC500s from Roskilde. The hardware, warranty and test documentation are JIMCO's; the stock, the quote by article number with no import surprises, and support in your time zone are ours. Tell us which spaces you need to reset, their rough volume and your available supply, and we will name the unit and quantity - and tell you where ozone is the wrong tool.
Compare the OZ1000, OZ1000T and OZ2000 See the MAC500s for occupied spacestech@sepcotech.com · ShipServ TN 317548
Tell us the spaces. We'll name the unit - or say ozone is the wrong tool.
Which spaces you need to reset, their rough volume and your available supply. Any units already in your quote list are attached below.
Enquiry Sent!
Thank you - your enquiry is on its way to the SepcoTech team. We'll reply within one business day.