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.
Even some so-called “experts” claim you need a True HEPA filter in your air purifier.
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.
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 |
| 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 |
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 H12 airflow allows it to remove more pollution from the air compared to the H13. Unfortunately, many air purifiers ignore the science and use the highest grade filter so they can market it based on filter grade .
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
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