Ozone for Cold Storage: Extending Shelf Life and Controlling Odour

What Is Ozone for Cold Storage?

Ozone for cold storage is the use of a low-concentration ozone gas, dosed continuously or in cycles into a refrigerated room or warehouse, to break down ethylene gas, kill mould spores and bacteria on contact, and neutralise the volatile organic compounds that cause musty, fishy or ammonia-like odours. Because ozone (O3) is generated on-site from ambient air or oxygen and decomposes back to oxygen within minutes, it leaves no chemical residue on packaging, walls, refrigeration coils or the produce itself.

This matters for cold storage operators for two separate reasons. First, ripening fruit, vegetables and cut flowers release ethylene gas continuously; ethylene accelerates ripening and senescence in nearby produce, so a closed cold room becomes a self-feeding cycle that shortens shelf life across every pallet in it. Second, cold, humid, poorly ventilated rooms are ideal breeding conditions for mould (especially *Botrytis*, *Penicillium* and *Rhizopus* species) and bacteria, both of which cause rot, weight loss and the persistent musty smell that lingers in warehouses long after the offending batch has been cleared out.

How Ozone Breaks Down Ethylene, Mould and Bacteria

Ozone is one of the strongest oxidants practically available for gas-phase treatment, and it acts on all three problems through the same mechanism: oxidation.

Ethylene (C2H4) reacts with ozone and is oxidised into carbon dioxide and water vapour, effectively pulling the ripening trigger out of the room's atmosphere before it can accumulate to levels that speed up senescence in surrounding produce. This is why ozone is used in banana, mango, grape and cut-flower cold rooms specifically to slow ripening rather than just to disinfect.

Mould spores and bacterial cell walls are oxidised on contact — ozone attacks the cell membrane directly, which is a physical rather than a metabolic kill mechanism, so resistance does not build up over repeated cycles the way it can with some chemical fumigants. Because the gas circulates with the room's air, it reaches surfaces that liquid sanitisers cannot: the underside of pallets, refrigeration coil fins, ceiling voids and door seals, which are exactly where mould colonises first in a cold room.

Ozone vs Chemical Fumigation for Cold Storage

Operators weighing ozone against sulphur dioxide pads, chlorine-based fumigants or manual chemical washdowns are usually comparing residue risk, labour and running cost, not just kill efficacy. The table below summarises the practical differences.

• **Residue on produce** — Ozone: none, decomposes to O2 | Chemical fumigants: possible residue, needs clearance time
• **Ethylene reduction** — Ozone: yes, direct oxidation | Chemical fumigants: no, not designed for this
• **Labour per cycle** — Ozone: automatic, no re-entry needed after purge | Chemical fumigants: manual application, PPE required
• **Odour after treatment** — Ozone: room smells neutral/'clean' within minutes of purge | Chemical fumigants: chemical smell can persist
• **Running cost driver** — Ozone: electricity only | Chemical fumigants: recurring consumable purchase
• **Worker re-entry** — Ozone: after ambient ozone clears (fast, minutes with ventilation) | Chemical fumigants: varies by product label

Dosing and System Design for Enclosed Cold Rooms

Cold storage ozone dosing is lower and more continuous than the shock-dose approach used for empty-room disinfection. A typical design separates two modes: a low-level maintenance dose (roughly 0.05–0.3 ppm, room-dependent) run continuously or cycled while produce is present, aimed at ethylene and airborne mould control without affecting stored goods, and a higher shock dose run only when the room is empty between batches, for full surface and coil disinfection before re-loading.

Getting this wrong in either direction is the single biggest cause of ozone cold-storage installations underperforming, so treat system sizing as an engineering exercise, not a guess.

• Calculate room volume (not floor area) including any adjoining corridors or anterooms served by the same air handler
• Confirm air changes per hour of the refrigeration/HVAC system, since ozone needs to circulate with existing airflow to reach every corner
• Match generator output (g/hr) to volume and target ppm, not to a generic 'per square foot' rule of thumb some vendors quote
• Specify ozone-compatible seals and gaskets on the generator and ducting — ozone degrades some standard rubber compounds over years of continuous dosing
• Include a residual ozone monitor with automatic cut-off if the room needs to be entered, and interlock it with the door/access system
• Plan for humidity: cold rooms run high relative humidity, which is generally favourable to ozone's oxidising reactions but the generator's dew-point tolerance should be checked at commissioning

Cost Reasoning: Is Ozone Worth It for a Cold Room?

The financial case for ozone in cold storage is built on shelf-life extension and rejection-rate reduction, not on the disinfection alone. Consider a mid-size cold room storing perishable produce worth roughly ₹8–10 lakh in stock value at any time, with a typical spoilage/rejection rate of 4–6% attributable to over-ripening and mould before intervention. A modest 1–2 percentage point reduction in rejection — a realistic outcome of controlling ethylene and mould rather than a guaranteed figure — already offsets several years of the generator's electricity draw, since ozone generators for a cold room of this size typically run on a few hundred watts continuously, a fraction of the refrigeration compressor's own load.

The other side of the ledger is what an operator no longer needs to buy: sulphur pads, fumigant consumables, and the labour hours spent on manual chemical washdown between batches. Because the ozone generator itself is the main capital item and running cost is essentially electricity, payback for most cold storage installations is driven far more by how much spoilage is currently being written off than by equipment price — which is why sizing the system correctly, per the checklist above, matters more to ROI than shopping for the cheapest generator.

Common Mistakes in Cold Storage Ozone Installations

Most underperforming installations trace back to a small set of avoidable errors.

• Undersizing the generator for total room volume, including unaccounted-for adjoining spaces on the same air loop
• Running only a shock dose and skipping continuous low-level dosing, so ethylene rebuilds between cycles
• Placing the ozone diffuser where it doesn't align with existing air circulation, creating dead zones near the door or ceiling
• No residual ozone monitoring, leaving staff re-entry timing to guesswork rather than measured ppm
• Ignoring ozone-resistant material selection for seals and ducting, leading to premature wear in continuous-dosing rooms
• Treating ozone as a substitute for basic cold-chain hygiene (regular pallet rotation, coil cleaning) rather than a complement to it

Where Lotus Ozone Fits

Lotus Ozone Tech has manufactured ozone generation equipment in Chennai since 2010, building every core component in-house — including our own DSC ceramic-electrode ozone cells — rather than importing generic cells and assembling around them. That in-house control is what lets us size a generator to an actual cold room's volume, air-change rate and dosing profile instead of selling off a fixed catalogue size. Our systems are running across more than 1,000 installations in India, spanning water, wastewater and air treatment applications including a project for the Department of Atomic Energy.

For cold storage specifically, our air purification technology covers the same oxidation principles used for ethylene and mould control described above, and our dedicated cold storage solution page details system configurations for produce warehouses and reefer facilities. If you're evaluating ozone for food processing more broadly, our guide on ozone in food processing covers dosing for wash lines and processing areas alongside storage.

Get a Cold Storage Ozone System Sized for Your Room

Ethylene load, room volume, air-change rate and produce type all change the right generator size and dosing profile for a cold storage installation — there isn't one number that fits every warehouse. Get a quote from our engineering team and we'll size a system against your room's actual specifications rather than a generic catalogue figure.