The Facts about HEPA Filters in Air Purifiers

Now more than ever, we have customers asking if HEPA filters can filter out viruses.

We cover this point in many of our other blogs but wanted to go into more detail in this blog. 

It would be rare to find an air purifier where the manufacturer actually tells you the grade of HEPA filter they are using in their purifier according to a particular standard. This is because few air purifiers would pass efficiency testing to a particular recognised standard such as EN1822. Clean Air Delivery Rate (CADR) formulated by the  Association of Home Appliance Manufacturers in the U.S.A. is a lower efficiency test and does not focus on ultra-fine particles; therefore, this rating system is not designed for commercial settings or the efficiency of particles the size of common viruses.  

The majority of air purifiers you find in stores use synthetic filters and will lose efficiency during the life of the filter, and the CADR rating does not take this into account. A tell-tale sign a HEPA filter is synthetic is when the manufacturer recommends changing after every 6 months of operation. 

What are the Different Types and Efficiencies of HEPA Filters?

Below is a chart of the different types of HEPA filters and their removal efficiencies according to EN 1822 standards (European and Australian Norm). Unfortunately, the term HEPA is used loosely because this wide classification covers everything from 85 - 99.99% efficiencies @ 0.3 microns. 
So when you purchase an air purifier, the big question is: are you buying one with 85% or 99.99% filtration and how would you know? Many air purifiers will advertise 99.95% efficiency without stating the micron size. The only way to really tell is to verify with the manufacturer if it's not clearly written in specifications.

H13 and H14 HEPA grades are commonly used in medical applications and H13 is the minimum grade HEPA filter that can be used in operating theatres in Australia.
Filter Class (EN 1822) Filter Class (ISO 29463) Overall Efficiency (%)
E11 ISO 15 E ≥ 95
E12 ISO 25 E ≥ 99.5
H13 ISO 35 H ≥ 99.95
H14 ISO 45 H ≥ 99.995
U15 ISO 55 U ≥ 99.9995
U16 ISO 65 U ≥ 99.99995
U17 ISO 75 U ≥ 99.999995

When it comes to virus filtration at approx. 0.12 microns in size you want a filter that goes as fine as possible. Airborne viruses are usually spread when the virus is aerosolised in fine droplets in the air, and these are typically 0.5 microns in size and larger. 
At INOVA Air Purifiers we only use H13 medical-grade HEPA paper in all of our HEPA filters.