ISO Class 5 is an atmospheric environment that contains less than how many particles of 0.5 microns in diameter per cubic meter of air?

ISO Class 5 is an atmospheric environment that contains less than how many particles of 0.5 microns in diameter per cubic meter of air?

• A. 352,000 particles 0.5 microns in diameter per cubic meter
• B. 3,520 particles 0.5 microns in diameter per cubic meter
• C. 3,520,000 particles 0.5 microns in diameter per cubic meter
• D. 352 particles 0.5 microns in diameter per cubic meter

Answer: (B)

ISO cleanroom classifications define the maximum number of airborne particles of a given size per cubic meter. For particles that are 0.5 microns in diameter, ISO Class 5 allows up to 3,520 particles per cubic meter of air. That makes 3,520 the correct limit for this class. Values higher than that correspond to poorer cleanroom classifications (ISO 6, 7, or 8), such as 352,000 or 3,520,000, which align with less stringent standards. The 352 per cubic meter option isn’t a standard limit for 0.5-micron particles in the ISO scale.

ISO cleanroom classifications define the maximum number of airborne particles of a given size per cubic meter. For particles that are 0.5 microns in diameter, ISO Class 5 allows up to 3,520 particles per cubic meter of air. That makes 3,520 the correct limit for this class. Values higher than that correspond to poorer cleanroom classifications (ISO 6, 7, or 8), such as 352,000 or 3,520,000, which align with less stringent standards. The 352 per cubic meter option isn’t a standard limit for 0.5-micron particles in the ISO scale.