True HEPA VS HEPA Type filter: What’s the Difference?
What Is True HEPA filter?
True HEPA filter is a mechanical filter that captures 99.97% of airborne particles as small as 0.3 microns e.g. dust mites, pet dander, mold, pollen, bacteria, and viruses. 0.3 um size is known to be the Most Penetrating Particle Size (MPP or MPPS) to bypass a filter. A true HEPA filter is rated between 17-20 MERV. It can be found in an HVAC system, vacuum cleaner, air conditioner, or air purifier. All True HEPA filters are not washable and have to be replaced.
* Take note that the European standard HEPA filter has a lower filtration efficiency of 99.95%.
What Is HEPA-type filter?
A HEPA-type filter is an inferior version to a True HEPA filter. It is gaining traction in the air purifier world due to the low cost with relatable efficiency. HEPA-type filter has a 99% efficiency rate or less at capturing particles as small as 2 microns. It is made out of thin fibers glass but with less density; finer particles like germs would be able to sneak past. A HEPA-type filter is rated between 13-16 MERV. It is commonly found in lower-end air purifiers. Some HEPA-type filters are washable and reusable.
What Are The Difference Between HEPA And True HEPA?
 True HEPA Filter |  HEPA-type Filter | |
| Efficiency | ||
|---|---|---|
| 99.97% efficiency on particles as small as 0.3 microns. | 90-99% efficiency on particles as small as 2 microns. | |
| Price Group | ||
| $80-300 | $30-100 | |
| MERV | ||
| 17-20 | 13-16 | |
| Filter Density | ||
| High | Medium | |
The main differences between HEPA-type and True HEPA filter are the filtration efficiency. In general, HEPA-type filter has a 99% efficiency rate for capturing particles as small as 2 microns. True HEPA filter up the game with a better 99.97% efficiency rate at particles as small as 0.3 microns. As both filters are widely used in the air purifier industry, HEPA-type filter is often paired with the cheaper, compact air purifier. True HEPA filter on the other hand, is tagged with the bigger, premium air purifier.
In short, go with a True HEPA filter if mold, pollen, bacteria, and viruses are your concern. These microbes can cause many respiratory problems and viral infections. If you want a cheaper filter but still retain the HEPA goodness, go with a HEPA-type filter. Consider a medical grade H13 HEPA air purifier if you want the absolute best filtration.
How Do I Tell What Type of HEPA filter an Air Purifier Is Hosting?
The best way to tell what type of HEPA filter is used in an air purifier is to screen through the specification from its manual or website. You can also check out the HEPA labeled score that should be printed on the box. Regardless of the filter naming convention, if is at a 99.97% filtration efficiency on particles as small as 0.3 microns, it is a True HEPA filter. Anything poorer than that would fall under the HEPA-type filter.
How Many Types of HEPA Filters?
As stated by the Institute of Environmental Science and Technology (IEST), there are six types of HEPA filters from A, B, C, D, E & F. Each has its characteristics and performance, as shown by the table below.
| Filter Type | Penetration Test | Scan Test | Efficiency Ratings | ||
|---|---|---|---|---|---|
| Method | Aerosol | Method | Aerosol | ||
| A | MIL-STD 282 | Thermal DOP | None | None | 99.97%/ 0.3 um |
| B | MIL-STD 282 | Thermal DOP | None | None | 99.97%/ 0.3 um |
| C | MIL-STD 282 | Thermal DOP | Photometer | Polydisperse DOP | 99.99%/ 0.3 um |
| D | MIL-STD 282 | Thermal DOP | Photometer | Polydisperse DOP | 99.999%/ 0.3 um |
| E | MIL-STD 51477 or MIL-STD F51068 | Thermal DOP | Photometer | Polydisperse DOP | 99.97%/ 0.3 um |
| F | IES-RP CC007 | Open | Particle Counter | Open | 99.999%/ 0.1 to 0.2 um |
A Little History About HEPA Filter
HEPA is an acronym for High-efficiency Particulate Air or High-efficiency Particulate Arrestance. A certified filter produced, tested, and labeled with recognized industry standards (DOE, IEST, UL). The first-ever HEPA filter was created in 1940 by American scientists for the Manhattan Project during World War II. The purpose is to prevent the spread of airborne radioactive contaminants from the atomic bomb. Over the next decade, it was commercialized and became a registered trademark filter.
What Is HEPA filter Made Of?
HEPA is a fibrous filter made from interlaced fine glass fibers with a diameter of less than 1 micron. The fine glass threads are tangled and compressed in myriad directions to form a filter mat. There are multiple folded sheets of fibrous material that increase the surface area and efficiency of the filter. A standard HEPA filter will have around 2,500 layers of glass threads.
How Does A HEPA Filter Work
When air is pulled towards the HEPA filter, the high-density filter fibers trap contaminants that pass through in either Direct Impaction, Diffusion, Sieving, and Interception. Direct Impaction happens when particles travel straight, collide, and are stuck with a fiber. Diffusion happens when ultrafine particles move volatilely, collide with fiber, and are stuck to it. Sieving happens when the particles are too large to pass through the gaps and get ensnared by surrounding fibers. Interception happens when Airflow is rerouting the particles around the fibers but will eventually stick to the sides of fibers. With harmful particles trapped and removed from the air, only clean air will be released back out. Allergic symptoms like sinus, cough, wheezing, headache, and breathing difficulty will gradually be alleviated.
Where Is A HEPA filter Used?
HEPA filters are often used in residential and commercial applications requiring airborne contamination control. With constant improvement over the years, HEPA filters can be found in nursery homes, hospitals, health care, and medical facilities. It is regularly used in manufacturing plants such as FMCG, CPG, disk drives, and pharmaceuticals. HEPA filters can also be found in advanced industries e.g. aerospace, semiconductors, automobiles, and nuclear power.
