Does an Air Purifier replace VMC?

No. An Air Purifier recirculates the same air (HEPA = particles), while VMC brings in fresh outdoor air and removes CO₂, humidity and odours. Ideally they are used together.

Is the ioniser worth it in an Air Purifier?

No. An ioniser removes only 20-30% of particles (vs 99.97% for HEPA) and produces ozone that irritates the lungs. If the unit has one, switch it off.

Does UV-C kill viruses in an Air Purifier?

In theory yes, in practice no. Air passes the lamp in fractions of a second - too little time for effective inactivation. UV-C works properly only in hospitals with specialist conditions.

Air Purifiers: HEPA, Ionisers, UV-C - What Actually Works

Shelves packed with "Air Purifiers" shouting buzzwords: HEPA, Ioniser, UV-C, Plasma, Photocatalysis. Some of these are real technologies. Some are pure marketing. And a €300 unit does something entirely different from your VMC system.

Let's sort it out: which device does what, which myths need to die, and when an Air Purifier is your ally - or false security.

1. HEPA H13: The True King of Filtration

HEPA stands for High Efficiency Particulate Air. A genuine HEPA H13 captures 99.97% of particles at 0.3 μm (MPPS - Most Penetrating Particle Size). At this size, pollen, dust mites, bacteria, mould spores and viruses all "stick" to the filter's micro-fibres.

HEPA H13 Air Purifier - particle filter PM2.5, pollen, dust mites, viruses

✅ Where it excels

Pollen/dust-mite allergies, pet dander. Children's rooms for allergy sufferers. Offices on busy roads (PM2.5). Patient rooms (viral load reduction). A proper HEPA H13 Air Purifier dramatically reduces inhaled particles.

❌ What it does NOT catch

Gases! CO₂, VOCs, formaldehyde, cooking odours. For gases you need Activated Carbon (a separate filter). Serious purifiers combine HEPA + Carbon.

📏 Key metric: CADR

Look for the CADR (Clean Air Delivery Rate) in m³/h. Multiply the room volume × 3 = the minimum CADR you need. E.g. 20 m² × 2.7 m = 54 m³ → CADR ≥ 162 m³/h.

💰 Running costs

HEPA filter replacement every 6-12 months: €40-80. Consumption: 30-60 W (Night mode) - less than a light bulb. Noise: 20-30 dB on low speed.

2. Ionisers: The Biggest Marketing Myth

Air ioniser - negative ions, marketing myth, ozone by-product

"Produces negative ions - like being near a waterfall!" This tagline sells millions of units. What does an ioniser actually do?

⚡ The theory

Negative ions "stick" to airborne particles, making them heavy so they fall onto floors and walls. The air "appears" cleaner. Problem: the particles haven't disappeared - they've just moved to your furniture, sofa and bed.

🦨 Ozone: the hidden danger

Many ionisers produce Ozone (O₃) as a by-product. Indoor ozone irritates the lungs, worsens asthma and causes headaches. The EPA explicitly discourages ion/ozone generators in enclosed spaces.

📉 Proven ineffectiveness

Studies show ionisation removes less than 20-30% of particles in real-world conditions - versus 99.97% for a HEPA filter. It does nothing for gases (CO₂, VOCs).

🚫 The recommendation

Avoid ionisers as a primary cleaning method. If your Air Purifier has a "bonus ioniser", switch it off - it adds nothing meaningful, just ozone.

3. UV-C: It Works - But Not How You Think

Ultraviolet radiation at 254 nm (UV-C) kills bacteria and inactivates viruses - this is true and well-documented. However, effectiveness depends on contact time and radiation intensity.

UV-C lamp 254nm - bacteria and virus disinfection, contact time critical

⏱️ Time vs reality

Air in an Air Purifier passes the UV-C lamp in fractions of a second. In that time, microbes don't have time to be "cooked". You'd need ten times the intensity - which doesn't fit in a household device.

🏥 Where it does work

In hospitals and laboratories: large ducts with slow airflow and powerful UV-C lamps. On surfaces: UV-C robots disinfect empty rooms (e.g. ICU wards). Contact time there is minutes, not milliseconds.

⚠️ In a home Purifier

The small UV-C lamp doesn't have time to inactivate viruses/bacteria at airspeeds that produce acceptable CADR. Slow the fan for "more UV dose" and the CADR plummets.

✅ Real value

In a home Air Purifier, UV-C may have small supplementary value - but should never be the primary method. Its presence is mostly marketing. Trust the HEPA.

4. VMC vs Air Purifier: Two Entirely Different Things

The most common myth: "I bought an Air Purifier, so I don't need ventilation." Wrong. They do completely different things - you may need both, but one doesn't replace the other.

VMC brings fresh outdoor air vs Air Purifier recirculates existing air

🔵 VMC = Fresh Air

Brings outdoor air indoors (with heat recovery). Removes CO₂, humidity, odours and VOCs. Filters the incoming air (F7). Replaces the air - it doesn't recirculate.

🟣 Air Purifier = Recirculation

Sucks in the same room air, filters it (HEPA) and blows it back. No fresh oxygen. No CO₂ removal. No humidity control. Removes particles only (and VOCs if it has active carbon).

🏆 The ideal combination

VMC (24/7 ventilation with recovery) + HEPA Air Purifier in the child's room or allergy sufferer's bedroom = ultimate air quality. VMC replaces stale air; the Purifier polishes the last remaining particles.

💡 Golden rule

If you must choose only one: pick VMC. Fresh air cannot be replaced by any filter. If you already have VMC and want "extra" protection, then an Air Purifier is an excellent complement.

🧹 HEPA = the only reliable method for particle filtration. Ionisers = marketing + ozone. UV-C = works only in specific conditions. And nothing replaces fresh air: VMC first, Air Purifier second.

Air Filter Guide (G4 to HEPA): Pressure Drop & Myths VOCs & Formaldehyde at Home: Risks and Solutions Sick Building Syndrome (SBS) & CO₂: Symptoms and Solutions What is Heat Recovery Ventilation (VMC / HRV)? Guide

Ventilation & Indoor Air Quality (IAQ)

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