What should a HEPA filter be capable of removing for it to be classified as such?

A HEPA (High-Efficiency Particulate Air) filter must be capable of removing particles of 0.3 microns in size at an efficiency rate of 99.97% or higher to meet the classification criteria. This level of efficiency means that when air passes through the filter, at least 99.97% of all airborne particles, including allergens, dust, and other contaminants, that are 0.3 microns in size are captured. The choice of 0.3 microns is particularly significant because this size is where particles tend to be most penetrating to filter systems, meaning that effective filtration at this size ensures greater efficiency across a wider range of particle sizes.

HEPA filters are particularly important in environments where air quality is critical, such as hospitals, laboratories, and homes with individuals who have respiratory issues, as they significantly reduce exposure to harmful particulate matter in the air. This makes B the correct choice, as it accurately reflects the standards required for HEPA classification.

While HEPA filters can capture a wide range of particle sizes, including those both smaller and larger than 0.3 microns, the defining specification for HEPA certification focuses on the 0.3-micron particle size because of its challenging