What is PCO (photocatalytic oxidation)?
In one line: PCO uses UV light shining on a catalyst (usually titanium dioxide) to drive chemical reactions that break down gases and germs. The theory is appealing, but real-world effectiveness is limited and some designs can produce ozone or incomplete by-products — which is why we favour HEPA + carbon.
How it's meant to work
UV light hits a titanium-dioxide-coated surface, creating reactive species that oxidise passing pollutants — in principle breaking down VOCs, odours and microorganisms into harmless carbon dioxide and water. It's marketed as "destroying" pollutants rather than just trapping them, which sounds like an upgrade on filters.
The real-world limits
- Contact time — air rushes past the catalyst too quickly for complete reactions, so removal of VOCs is often modest in practice.
- Incomplete oxidation — partial reactions can create new by-products (e.g. formaldehyde or other irritants) rather than harmless end-products.
- Ozone risk — some UV/PCO designs generate ozone, a lung irritant (why that matters).
- No particle removal — PCO doesn't capture dust or PM2.5; you still need a filter for those.
The practical takeaway
Independent testing has generally found PCO less effective than manufacturers claim for real rooms, and the by-product/ozone questions are a real downside. For dependable, safe home air, mechanical filtration — HEPA for particles, activated carbon for gases and odours — remains the proven approach.
Next step
Prefer proven, ozone-free filtration? Browse HEPA + carbon units in the CleanAirKits store.
FAQ
Does PCO air purification work? In theory it breaks down gases and germs, but real-world effectiveness is limited by contact time and it can create by-products. Filtration is more reliable.
Is PCO safe? Some designs can emit ozone or incomplete-oxidation by-products. If you want to be sure, choose sealed HEPA + carbon with no UV/PCO stage.