HEPA vs HEPA-type explained
HEPA is a performance standard, not a material. A filter earns the name by capturing at least 99.97 percent of particles 0.3 microns in size, the size that is hardest to catch; both larger and smaller particles are captured at higher rates.
The labels you'll see
- True HEPA: meets the 99.97 percent standard. The marketing word "true" exists because of the next entry.
- H13 / H14: European grades. H13 is 99.95 percent, H14 is 99.995 percent, both effectively HEPA. Fine for home use.
- HEPA-type, HEPA-like, HEPA-style, 99 percent HEPA: not HEPA. These typically capture 85 to 99 percent of larger particles and much less of the smallest. We do not count them as HEPA, and the true HEPA rating on each model page reflects that.
- Medical-grade: no defined meaning in consumer products. Ignore it.
Why the seal matters more than the grade
Air takes the path of least resistance. A HEPA filter in a housing with gaps lets air bypass it, and a well-sealed H11 filter can outperform a leaky H14. This is why we rank on measured CADR rather than filter grade: CADR is measured on the whole unit, leaks included. A unit with a high CADR for its size has a good seal by definition.
Smaller than 0.3 microns
A common worry is that viruses and the finest smoke particles slip through. They don't, mostly: below about 0.1 micron, particles move erratically enough that they collide with filter fibers more often, not less. The 0.3 micron figure is the standard because it is the worst case.
Filter life
A HEPA filter doesn't stop working when it gets dirty; it gets more restrictive, so airflow and CADR fall. Replacement intervals in our filter cost figures use each maker's stated interval; heavy use shortens it.