Are True HEPA Filter Air Purifiers Better?

Many air purifier companies market their air purifiers as “True HEPA” air purifiers. For example, Philips touts the True HEPA filters in their air purifiers and its filtration efficiency.

Are True HEPA filters better?

Even some so-called “experts” claim you need a True HEPA filter in your air purifier.

Are True HEPA filters better?

So what exactly are True HEPA filters, and are they better?

True HEPA Filters: A Vague Marketing Term

True HEPA is a marketing term with no legal or scientific meaning. In fact, a True HEPA is simply a HEPA filter. Although there are different HEPA filter grades, “True HEPA” does not specifically refer to any one of them.

HEPA Filter Ratings

If you want to understand the filtration efficiency of a HEPA filter, look for the rating of the HEPA filter, rather than the “True HEPA” term. There are various HEPA filter standards set by different countries and organizations. Each standard has a different definition of the filtration efficiency of a HEPA filter.

HEPA filter standards

Two common air filter standards are ASHRAE’s MERV standard and the EN 1822 standard.

Filter Class (EN 1822)Filter Class (ISO 29463)Overall Efficiency (%)
E10 (H10)– (not covered)≥ 85
E11 (H11)ISO 15 E≥ 95
E12 (H12)ISO 25 E≥ 99.5
H13ISO 35 H≥ 99.95
H14ISO 45 H≥ 99.995
U15ISO 55 U≥ 99.9995
U16ISO 65 U≥ 99.99995
U17ISO 75 U≥ 99.999995

Myth: Higher Grade Filters Are Better

Air purifier companies like to market their HEPA filters as the highest-grade, highest-efficiency filters. But the truth is surprising: a weaker filter can make for a BETTER air purifier. How can this be?

The problem is a higher-grade filter comes at a cost. That cost is airflow. Higher-grade HEPA filters will capture more particles, but they’ll let less air through. Thus, there’s a sweet spot in the tradeoff between airflow and particle capture.

Weaker Filter Outperforms

We at Smart Air tested this with our own Sqair HEPA air purifier. The increase in airflow of a weaker H11 airflow allows it to remove more pollution from the air compared to the H12. Unfortunately, many air purifiers ignore the science and use the highest grade filter so they can market it based on filter grade .

HEPA filter efficiency

So How Should You Determine An Air Purifier’s Effectiveness?

The type of HEPA filter used does not tell you much about the effectiveness of an air purifier. A more useful measure of air purifiers is their overall effectiveness. Clean air delivery rates (CADR) are an official way to measure how much clean air an air purifier puts out.

Read More: 4 Steps to Choosing the Best Air Purifier

Bottom Line: True HEPA Is Just A Marketing Term

A True HEPA filter is a marketing term with no legal or scientific meaning. Check a HEPA filter’s rating for more information on filtration efficiency. But beware: less efficient filters can make for better air purifiers.

Smart Air


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Smart Air is a social enterprise that creates simple, no-nonsense air purifiers and provides free education to protect people’s health from the effects of air pollution. We are proud to be the only certified B-Corp dedicated to fighting air pollution.