What ISO Class is specified for HEPA filters?

• A. Class 3
• B. Class 5
• C. Class 7
• D. Class 9

Answer: (B)

Air cleanliness for handling hazardous drugs relies on HEPA filtration to meet ISO Class standards. ISO Class defines how many particles of a given size are allowed in a cubic meter of air. For the critical work area where sterile compounding or containment occurs, ISO Class 5 is the typical requirement. HEPA filters are designed to remove at least 99.97% of particles as small as 0.3 microns, which helps achieve and maintain that ISO 5 level of cleanliness. The other classes represent environments that are either much cleaner or less clean than what’s needed for safe sterile work, so they aren’t the standard target for HEPA-filtered compounding areas.