Clean Air Glossary
New to air-purifier jargon? Here's every key term in plain English. Each links to a fuller explanation on our independent reference site, Air Purifier Directory.
The essentials
- Air purifier — a device that draws room air through filters to remove pollutants and returns cleaner air.
- How an air purifier works — fan → pre-filter → particle filter → (carbon) → clean air, repeated many times an hour.
- CADR — clean-air delivery rate: how much clean air a unit delivers per hour. The key spec.
- ACH — air changes per hour: how many times it replaces a room's air each hour.
- ACH vs CADR — how the two relate, and which to use when.
Particles & pollutants
- PM2.5 — fine particle pollution under 2.5 microns; the main health concern.
- VOCs — gases from paint, cleaning products and furnishings; need carbon, not a particle filter.
- AQI — air quality index: pollution levels as a single number and colour.
- Air quality monitor — measures PM2.5, CO2 and VOCs so you can see and act on problems.
Filters
- HEPA vs MERV-13 — two ways to capture fine particles, and why airflow often matters more than grade.
- HEPA (H13/H14) — what the true-HEPA grades capture.
- True HEPA vs “HEPA-type” — why the qualifier matters.
- Activated carbon filter — removes gases and odours a particle filter can't.
- HEPA vs carbon — particles vs gases: which you actually need.
- Pre-filter — the coarse first layer that protects the main filter.
Designs & technologies
- Corsi-Rosenthal box — the high-airflow, low-cost MERV-13 design.
- Ionisers & ozone — how they differ from filters, and the ozone caveat.
- Negative ions — what they are and whether ionic purifiers clean air.
- UV-C — do UV-C purifiers work, and are they safe?
Choosing & sizing
- What size do I need — match CADR to your room.
- Sq ft ↔ m² — convert coverage areas.
- Where to place it — the best position for airflow.
- Running cost — how much electricity purifiers use.
Browse the full reference at airpurifierdirectory.com.