How the technology works: HEPA, UV-C, ions and plasma

Where this conversation usually starts

Most buyers reach this page after a sales call full of terms nobody defined: "ionised", "photocatalyst", "medical-grade", "kills 99.9%". The honest starting question is simpler than the jargon suggests — is this an air purifier or an air steriliser, and does a clinic actually need the difference. A domestic HEPA unit traps particles rather than treating them. Whether that gap matters depends on the setting, which is what separates a medical-grade unit from a consumer one in practice rather than on the box.

Size the room before you compare technology

Technology comparisons are pointless if the unit is the wrong size for the room, so sizing comes first. Required clean-air delivery rate (CADR, in m³/h) equals floor area (m²) × ceiling height (m) × target air changes per hour (ACH). US CDC guidance sets a floor of at least 5 clean-air changes per hour for an occupied space. At 5 ACH, a room clears 99% of an airborne contaminant in roughly 55 minutes; push to 10 ACH and that drops to about 28 minutes, to 15 ACH and it is closer to 18 — a difference that comes entirely from air changes, not from which stage sits inside the unit. Our sizing calculator does this arithmetic for a specific room, and whether a unit is worth its technology claims starts with whether it is even correctly sized, which our honest look at whether air purifiers actually work covers first.

How the stack works, stage by stage

A medical-grade unit is not one filter — it is a sequence of stages, each doing a specific job, and the sequence matters as much as any individual layer. Our guide to the seven-layer filtration stack walks through the full sequence; here is what each stage is for.

Pre-filter

The washable pre-filter is the first mechanical barrier, catching hair, lint, larger dust and coarse particles before they reach the finer, more expensive stages behind it. Its job is protective — extending the working life of everything downstream — rather than doing the fine filtration itself.

Cold catalyst

Cold catalyst filtration works at room temperature to break down certain gaseous pollutants without needing heat or a separate energy source. It is a distinct process from activated carbon, and our guide to cold catalyst filtration sets out where it fits without the marketing gloss usually layered on top of it.

Activated carbon

Activated carbon adsorbs odour molecules and volatile organic compounds — cooking smells, cleaning agents, off-gassing from furnishings — rather than airborne particles or pathogens. It is doing a different job from HEPA, not a weaker version of the same job, which our guide to activated carbon filtration explains in more detail.

Antibacterial layer

An antibacterial-treated layer sits ahead of the HEPA stage to reduce microbial growth building up on the filter media itself over weeks of continuous use, rather than treating the air passing through it directly. It is a housekeeping stage for the filter, not a stand-alone treatment claim.

H13 HEPA

H13 HEPA is a specific efficiency grade, capturing particles down to 0.1 micron — a materially finer standard than the H10 to H12 grades sometimes sold under the general "HEPA" label. Our guide to the H13 micron rating sets out exactly what that number means. What HEPA does not do is treat what it captures: it traps particles, including viruses and bacteria, rather than neutralising them, which is why the filter medium itself can hold viable organisms after capture — our guide to whether HEPA filters kill viruses covers this distinction directly.

UV-C

UV-C light acts on organisms held in the filter media, working alongside HEPA rather than replacing it. The safety question buyers raise most is whether an enclosed UV-C lamp design is sound and whether it produces ozone as a by-product — our honest look at UV-C safety and our guide to the ozone question both address this directly rather than skipping past it.

Anion release and copper-silver ion

Anion release and copper-silver ion treatment are two separate mechanisms, not duplicate marketing terms for the same feature. Anions attach to airborne particles, encouraging them to settle out of the air faster, which our guide to anion release sets out plainly. Copper-silver ion sterilisation targets organisms on a different pathway from UV-C, working alongside it rather than repeating it, as our guide to copper-silver ion sterilisation explains.

What the chamber test showed, and its limits

Under chamber-test conditions, the active stages in AIRE's units eliminated over 99.99% of the tested organisms — E. coli, Staphylococcus albus and Influenza A — within 60 minutes. A comparison run using plain HEPA filtration alone, relying on passive decay with no active treatment stage, took roughly 4 hours 23 minutes to reach a comparable reduction. That gap is the practical argument for an active stage behind the HEPA layer. It is also a controlled result, not a promise: a sealed chamber has no open doors, no foot traffic and no continuous new air being drawn in, so results in occupied rooms may differ from the chamber figure.

Matching the unit to the room

Once a room is sized, the technology stack needs to sit inside a unit that actually fits the space. The Fillo Plus suits rooms up to 30 m² with a CADR of 300 m³/h, running under 53 dB, and pairs H13 HEPA with UV-C and Tuya WiFi connectivity for app-based monitoring — our guide to Tuya WiFi integration covers what that adds for a networked clinic setup. The Classic 400S covers 31–54 m² with the full seven-layer stack and a 480 m³/h CADR, running between 30 and 55 dB depending on fan speed. The Pro 800S is built for larger spaces, 56–96 m², with dual intake, castors for repositioning, a built-in PM2.5 sensor and a 26 dB sleep setting — our guide to reading a PM2.5 sensor explains what that on-board reading is measuring and its limits. Sensor-driven models also run a Smart Auto mode that adjusts fan speed to the reading rather than a fixed preset. Home settings are covered separately by the Reno 500S, a 20–40 m² plasma-ion unit with no filter changes, and the compact KJ100F desktop unit for a single workstation.

What we will not claim

We will not state that any unit reduces infections, sick days or any other health outcome — chamber-test results are a controlled measurement, not a clinical claim, and we will not describe treated air in absolute terms the test does not support. We do not claim approval from a Singapore health regulator, because that does not apply to a consumer or clinical air purifier in this market. AIRE units carry an FDA Class 2 medical device listing held by the manufacturer, H13 HEPA specification, CE and RoHS marking, and ISO 9001 and ISO 14001 management system certification — what each of those actually covers is set out on our verification page.

The next step is measuring your rooms, not comparing spec sheets

Technology comparisons only mean something once applied to your actual rooms. A Clinic Air Report costs S$150 per site visit, covers a minimum of two rooms, and measures every room on site rather than estimating from a floor plan — the report is emailed within two working days, with a sized-right guarantee: if a specified unit does not reach the report's air-change figure once installed, we upgrade or add a unit at no extra cost. From there, our product range, our solutions by setting, and our contact page are the next steps.