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Activated Carbon Filter vs HEPA: What's the Difference?
Shopping for an air purifier, you'll see two filter types named again and again: HEPA and activated carbon. It's easy to assume they're rival versions of the same thing — pick the "better" one and move on. They're not. Each targets a completely different kind of pollutant, here's what actually separates them.
Quick comparison
|
HEPA |
Activated carbon |
|
|
Removes |
Solid particles |
Gases, odours, VOCs |
|
Catches |
Dust, pollen, mould, dander, smoke particulate |
Cooking/pet smells, formaldehyde, paint & solvent fumes |
|
How |
Mechanical capture |
Adsorption (gases stick to the surface) |
|
Blind spot |
Can't touch gases |
Can't trap fine particles |
What HEPA does
HEPA stands for High-Efficiency Particulate Air. Per the US EPA, a true HEPA filter removes at least 99.97% of airborne particles, using a standard defined by the U.S. Department of Energy. The famous 0.3-micron figure is the hardest case — particles both larger and smaller are caught even more efficiently. Its limit: HEPA only works on things with physical size. Gas and odour molecules pass straight through.
What activated carbon does
Carbon covers that gap. It's charcoal processed to be extraordinarily porous — hundreds to thousands of square metres of surface area per gram.
Gas molecules cling to that surface through adsorption; a peer-reviewed review on VOC adsorbents explains the mechanism. This targets the pollutants HEPA misses.
Why you need both
Indoor air is a mix of particles and gases. The practical answer is a layered stack: a pre-filter for large debris, a HEPA layer for fine particles, then a carbon layer for gases.
All PRISM+ air purifiers are built around this layered approach. Our filters use a 3-in-1 filter — pre-filter, HEPA H13, and activated carbon for odours, formaldehyde and other gases.