HEPA stands for

• A. High Efficiency Particulate Air filter
• B. Ultra-Low Particulate Air filter
• C. Air Changes Per Hour
• D. Containment Primary Engineering Control

Answer: (A)

HEPA filters are defined by their high-efficiency filtration of particulates from the air. The full expansion of the acronym is High Efficiency Particulate Air filter. This means the filter is designed to capture a very large fraction of small particles as air passes through it, with standard tests showing about 99.97% efficiency for particles around 0.3 microns. That level of performance makes HEPA filtration essential in environments where keeping airborne contaminants down is crucial, such as hazardous drug compounding, where HEPA-equipped containment devices help protect both the worker and the product. The other terms don’t fit because they refer to different concepts: an ultra-low particulate air designation isn’t a recognized standard; air changes per hour describes how often air is replaced, not what the filter is called; and containment primary engineering control refers to the equipment class rather than the filter’s name.