The letters H-E-P-A represent the words HighEfficiencyParticulateair. HEPA filters capture almost all particles in the air that are zero point three microns in size or larger.
On most commercial planes, at least half of the air comes from outside the aircraft and passes through a high-efficiencyparticulateair, or HEPA, filter which removes contaminants
在多数商用飞机上，至少有一半空气是来自于飞机外部，而且都经过了一种高效空气净化装置的过滤。
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Inside your home, use a high-efficiencyparticulateair (HEPA) purifier capable of removing PM2.5 particles, or install such a filter in your heating system.