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The full form of HEPA is High Efficiency Particulate Air. These are mainly used for the filtration of air. The HEPA filters are classified into different classes based on the efficiency of retention of air particles. The HEPA filters were designed in 1940’s.

            The classification was done by standards of United States Department of Energy (DOE), Based on the efficiency 99.97% of 0.3 µm particles.

HEPA Class

Retention (total)

Retention (local)

E10

>85%

---

E11

>95%

---

E12

>99.5%

---

E13

>99.95%

>99.75%

E14

>99.995%

>99.975%

U15

>99.9995%

>99.9975%

U16

>99.99995%

>99.99975%

U17

>99.999995%

>99.9999%

 

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