HEPA stands for High Efficiency Particulate Air, and like the name says, these filters are designed to remove 99.97% of all airborne pollutants 0.3 microns or larger from the air that passes through the filter (these include tobacco smoke, household dust and pollen) which represents an extremely high filtration capability. This level of filtration can be very helpful for those managing asthma or allergies.

One of the best strategies is to keep away from allergens; this level of filtration can help you to do that.

The "True" HEPA filter was developed during World War II by the Atomic Energy Commission and it was designed to remove and capture radioactive dust particles from the air which might escape and present a health hazard to the researchers.

For a filter to be labeled "True" HEPA, it must be certified at least 99.97% efficient in capturing 0.3 micron respirable-size-particles (RSP) according to the U.S. Military Standard MIL-STD-282, commonly known as the DOP test.

Winix PlasmaWave™ Air cleaner 9000 series’ True HEPA filter boast 99.99% efficiency surpassing our competitors’ 99.97% efficiency.

Winix 4-in-1 Replacement HEPA Filter Cassette contains FOUR filtration systems in one cassette – they are effective and a money-savor!


Filtration 1: Washable Anti-Bacterial Pre-Filter
This reusable filter collects large airborne particles such as pollen, dust, pet hair and lint, etc.

Filtration 2: True HEPA Filter*
Captures 99.99%* of particles and impurities as small as .3 microns including smoke, dust, pollen, mold spores, and pet dander.

* In case of 9000 series. 5000 series are equipped with 99.97% True HEPA filter. 5000B is equipped with 99% HEPA filter.

Filtration 3: Nano-Silver Mesh
A shield of silver particles one billionth of a meter in size neutralizes bacteria on contact.

Filtration 4: Washable Carbon Filter
Activated granular carbon effectively collects chemical vapors and odors caused by cigarette smoke, organic decay and cooking.

Note: 5000B uses 2-stage filtration system with Carbon Pre-Filter and 99% HEPA filter.