The difference between a HEPA filter and an air purifier is that a HEPA filter is a part of an air purifier, it's just the filter. An air purifier is a larger machine and it is made up of a filter, a fan, a body, and any other system it may have.

HEPA filters are just one piece of the package, something you're supposed to replace easily when needed. An air purifier, being the whole machine, is not what needs to be replaced.

The reason why so many air purifiers are called "HEPA air purifiers" and other similar expressions is that the HEPA filter is one of the most important parts of the air purifier. Without a filter, the air purifier would not work.

Not all air purifiers come with a HEPA filter, and so it's the fact that an air purifier comes with a HEPA filter that makes it special. This is what people look for when buying an air purifier consumer reports. The identity of the air purifier is linked to the filtration system it uses.

There are other air purifiers that also take their name from their filters and systems. One of these air purifiers is a water-based air purifier, which as you can see uses water as a filter.

So what is a HEPA filter?

A HEPA filter is a specialized type of filter that was originally created as part of the Manhattan Project (where the United States developed the atomic bomb). It was designed to capture hazardous radioactive materials from the air.

Over time, people learned that these same filters could be of great use in homes as well. These filters can capture 99.97% of particles larger than 0.3 microns. It's rather small! How small? Well, it's about 57 to 603 times smaller than human hair. (This range exists because some people have thicker hair than others).

So why is it important?

Particles smaller than 0.3 microns are incredibly small, as you may have noticed. The fact that HEPA filters can filter such small particles bodes well for us, because dust, pollen, dander, and tons of other particles floating around in the air are all larger than 0.3 microns. As such, a HEPA filter can pull them out of the air.

But HEPA filters don't stop there. Many air purifiers with HEPA filters incorporate other filters. These other filters include activated carbon filters and pre-filters, both of which can help you get better, cleaner air.