Which statement accurately describes HEPA efficiency as stated in the material?

Which statement accurately describes HEPA efficiency as stated in the material?

• A. Filters down to 90% of particles equal to 0.3 micrometers
• B. Filters down to 99.97% of particles equal to or larger than 0.3 micrometers
• C. Filters down to 99.99% of particles equal to 0.3 micrometers
• D. Filters down to 99.97% of particles equal to 0.1 micrometers

Answer: (B)

HEPA efficiency is defined by how well the filter performs at the most challenging particle size, which is 0.3 micrometers. A true HEPA filter must remove at least 99.97% of particles at that size, and typically also does at least that well for particles at or larger than 0.3 μm. That makes the statement describing 99.97% efficiency for particles equal to or larger than 0.3 μm the correct description. The other options don’t fit because they either claim a lower or higher efficiency, or specify a different particle size (0.1 μm) that isn’t the standard rating for HEPA.

HEPA efficiency is defined by how well the filter performs at the most challenging particle size, which is 0.3 micrometers. A true HEPA filter must remove at least 99.97% of particles at that size, and typically also does at least that well for particles at or larger than 0.3 μm. That makes the statement describing 99.97% efficiency for particles equal to or larger than 0.3 μm the correct description. The other options don’t fit because they either claim a lower or higher efficiency, or specify a different particle size (0.1 μm) that isn’t the standard rating for HEPA.